P0420 and Voltages at Sensors...Please Explain
03-10-2008, 02:12 PM
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P0420 and Voltages at Sensors...Please Explain
While getting the other work done at Limbaugh today, I had them check the voltages on the sensors with their massive OBDII hand held. If I read them correctly (and the screen was awfully dirty), here is what they read....
B1 S2 Varied between 0.09 and 0.75 mV
B1 S1 Stayed pretty constant right at 3.25 mV
This was with the engine in park and him reving it to 2500 rpms. Is the first sensor listed the one after the cats and the other the one in front of the cats? I seem to recall reading that if the after cat sensor's voltage jumped around then that indicated a problem with the converters. My problem...I don't know if I got the right readings or which of these is which. Can someone shed some light on this for me? Thanks.
Matt
B1 S2 Varied between 0.09 and 0.75 mV
B1 S1 Stayed pretty constant right at 3.25 mV
This was with the engine in park and him reving it to 2500 rpms. Is the first sensor listed the one after the cats and the other the one in front of the cats? I seem to recall reading that if the after cat sensor's voltage jumped around then that indicated a problem with the converters. My problem...I don't know if I got the right readings or which of these is which. Can someone shed some light on this for me? Thanks.
Matt
03-10-2008, 03:30 PM
#2
A couple of things about that code:po420 Catalyst system efficiency below threshold.
From Toyota Engine Control systems 2,Course 874 Technician Handbook:
Catalyst effiency is monitored by comparing the pre-catalyst O2 or A/F sensor output signal with the signal recieved from the post-cat O2 sensor.The ECM uses voltage variations between these sensors to measure the catalyst performance.
When the converter is operating properly,the post-catalyst sensor is significantly less active than the pre-cat sensor.This is because the converter stores and releases oxygen as needed during its reduction and oxidation process,thus the post-cat sensor is exposed to exhaust gasses with very little variation in oxygen levels.
The sub-sensor signal will make slow transitions in voltage,however,they occur over long periods of time.The sub-sensor signal from a catalytic converter that is NOT functioning properly will have a pattern with a frequency and amplitude similar to the main O2 sensor when viewed in waveform.
Note: After the engine and catalyst are warmed up and the conditions listed are met,the ECM will run the catalyst monitor (test).Catalyst warm-up is determined by calculation in the ECM's internal programming.Engine load,engine coolant temp,and run time are the primary factors used to determine catalyst temp.
......
So basically to test for the code you have to meet all the vehicals test criteria.Drive the vehical,while driving you have to monitor the scan tool oscilloscope of both the pre and sub sensors(just sitting and reading voltages without load on the engine will not get the ECM into "cat test monitor"),And if they start to move at all in the same frequency ECM store/throws a code po420....
SOOOO....99% chance you have a bad cat...Sorry
From Toyota Engine Control systems 2,Course 874 Technician Handbook:
Catalyst effiency is monitored by comparing the pre-catalyst O2 or A/F sensor output signal with the signal recieved from the post-cat O2 sensor.The ECM uses voltage variations between these sensors to measure the catalyst performance.
When the converter is operating properly,the post-catalyst sensor is significantly less active than the pre-cat sensor.This is because the converter stores and releases oxygen as needed during its reduction and oxidation process,thus the post-cat sensor is exposed to exhaust gasses with very little variation in oxygen levels.
The sub-sensor signal will make slow transitions in voltage,however,they occur over long periods of time.The sub-sensor signal from a catalytic converter that is NOT functioning properly will have a pattern with a frequency and amplitude similar to the main O2 sensor when viewed in waveform.
Note: After the engine and catalyst are warmed up and the conditions listed are met,the ECM will run the catalyst monitor (test).Catalyst warm-up is determined by calculation in the ECM's internal programming.Engine load,engine coolant temp,and run time are the primary factors used to determine catalyst temp.
......
So basically to test for the code you have to meet all the vehicals test criteria.Drive the vehical,while driving you have to monitor the scan tool oscilloscope of both the pre and sub sensors(just sitting and reading voltages without load on the engine will not get the ECM into "cat test monitor"),And if they start to move at all in the same frequency ECM store/throws a code po420....
SOOOO....99% chance you have a bad cat...Sorry
03-10-2008, 03:46 PM
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My only question is how fast was B1S2 switching between 0.09 and 0.75 mV? Was it quick like every second or two of was it more like a 20-30 second cycle between high and low voltage. There are a lot of arguments on here about P0420 but the fact is that if your rear sensor (B1S2) is switching quickly then your CAT is not working. I like to use the front sensor as a reference. If they are switching close to the same rate (~1-2 seconds) then the CAT is bad. The rear sensor on a vehicle with a good CAT will stay steady at around 0.1-0.2 V (lean) for a long period of time (20-30 seconds or even longer).
Have you had any other problems with your rig? Misfire, run it out of gas, recent CEL? Usually a bad CAT is caused by some other lean air fuel ratio condition.
Have you had any other problems with your rig? Misfire, run it out of gas, recent CEL? Usually a bad CAT is caused by some other lean air fuel ratio condition.
03-10-2008, 03:50 PM
#4
Oh, and the B1 S1 is the sensor before the cat,yours is an A/F sensor(3.25 mv)...
And the B1 S2 is the sensor after the cat(regular old O2 sensor)...
So it should be rock solid..if it swings in voltage,its picking up that the cat is not working.
And the B1 S2 is the sensor after the cat(regular old O2 sensor)...
So it should be rock solid..if it swings in voltage,its picking up that the cat is not working.
03-10-2008, 06:32 PM
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No it was switching quickly...like every couple of seconds. Sounds like I've got a bad cat. Problem is....I've got a California emissions equipped truck so I don't know if it's the front one, the back one, or both! I guess it's just when do I want to drop $1,500 on new OEM cats. This sucks! I'll just keep putting up with it before I spend that much on catalytic converters, especially when there has been no loss of performance what so ever. Thanks guys.
Matt
Matt
03-10-2008, 06:50 PM
#7
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This solved my P0420 CEL:
http://www.urdusa.com/product_info.p..._id=1230100014
I too have a 2 cat ECU, but I'm only running one cat.
http://www.urdusa.com/product_info.p..._id=1230100014
I too have a 2 cat ECU, but I'm only running one cat.
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03-11-2008, 02:37 AM
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If I were you I'd drop by or call your local Toyota dealer. I beleive you may have a 7 or 8 year emissions warranty on that car. If so you'd get your CATs (both of them) replaced for FREE!
No it was switching quickly...like every couple of seconds. Sounds like I've got a bad cat. Problem is....I've got a California emissions equipped truck so I don't know if it's the front one, the back one, or both! I guess it's just when do I want to drop $1,500 on new OEM cats. This sucks! I'll just keep putting up with it before I spend that much on catalytic converters, especially when there has been no loss of performance what so ever. Thanks guys.
Matt
Matt
03-11-2008, 03:25 AM
#9
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03-11-2008, 04:15 AM
#10
in a normal system, you are looking at the waveform, not voltage numbers.
rear sensor in cali vehicle should be flat line pretty much always
california:
the waveform of the before cat air fuel sensor will be spiky, with fairly level,
smaller sine wave intervals during the toyota test
the waveform of the after cat oxygen sensor should be a flat line
on non-cali vehicles the before cat o2 sensor will be sinewave, and the
after cat will not be flat line
----------
warm up vehicle
then stay at 3000 rpm for 3 minutes
now enter testing phase
2 second intervals at 2000 rpm, then back to 3000 for 2 seconds,
and repeat. here is where you look at the waveforms, when you are
doing the 2 sec at 3000, 2 sec at 2000, ...etc...
-----
ALSO note, it is impossible to confirm A/F sensor voltage with any OBD II or Toyota scan tool, so don't
base any decisions on readings from b1 s1. it is basically a fixed value.
What you can determine, is an open or short. The ECU controls
the voltage, not the sensor itself. You are looking for either an open or short which a scan
tool can tell you, but the actual operation of the sensor cannot be determined.
rear sensor in cali vehicle should be flat line pretty much always
california:
the waveform of the before cat air fuel sensor will be spiky, with fairly level,
smaller sine wave intervals during the toyota test
the waveform of the after cat oxygen sensor should be a flat line
on non-cali vehicles the before cat o2 sensor will be sinewave, and the
after cat will not be flat line
----------
warm up vehicle
then stay at 3000 rpm for 3 minutes
now enter testing phase
2 second intervals at 2000 rpm, then back to 3000 for 2 seconds,
and repeat. here is where you look at the waveforms, when you are
doing the 2 sec at 3000, 2 sec at 2000, ...etc...
-----
ALSO note, it is impossible to confirm A/F sensor voltage with any OBD II or Toyota scan tool, so don't
base any decisions on readings from b1 s1. it is basically a fixed value.
What you can determine, is an open or short. The ECU controls
the voltage, not the sensor itself. You are looking for either an open or short which a scan
tool can tell you, but the actual operation of the sensor cannot be determined.
Last edited by edzo; 03-11-2008 at 04:27 AM.
03-11-2008, 06:23 AM
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Who or where should I take the truck to get these voltages checked? A dealer...another place like Meineke or something? Thanks!
BTW...I will call Toyota and see if I'm still under the emissions warranty. I'd rather that than the local dealers.
Matt
BTW...I will call Toyota and see if I'm still under the emissions warranty. I'd rather that than the local dealers.
Matt
03-11-2008, 06:48 AM
#12
you really don't want voltages. you want the waveforms.
the voltage you mention for b1s1 is fine. unlike an o2 sensor, that voltage is determined by the ECU anyway. but it is in range of normal
the voltage for the rear o2 sensor should be flat line basically. if it is spiking then yes maybe cat efficiency is gone
-
it is almost certain that you have a bad cat. if your sensor front or back was actually bad it is likely you'd be getting more codes than 0420. You also be getting 0125 and possibly others if the signals from the sensors were out of spec. if all you get is 0420 chances are the cat is used up
the voltage you mention for b1s1 is fine. unlike an o2 sensor, that voltage is determined by the ECU anyway. but it is in range of normal
the voltage for the rear o2 sensor should be flat line basically. if it is spiking then yes maybe cat efficiency is gone
-
it is almost certain that you have a bad cat. if your sensor front or back was actually bad it is likely you'd be getting more codes than 0420. You also be getting 0125 and possibly others if the signals from the sensors were out of spec. if all you get is 0420 chances are the cat is used up
Last edited by edzo; 03-11-2008 at 07:07 AM.
03-11-2008, 07:05 AM
#13
To answer your question about the front or rear cat.It's probably both.If the sub2 is switching,basically it means that the cat(s) inbetween the front and rear sensors are not working(S1-S2).It would be possible that the front one went bad and if caught quick enough you could just replace that one,but once it goes the rear one gets overworked and then goes bad.
In my area of the country we had a problem when they decided to start reformulating fuel,This fuel was full of sulfur.Started seeing tons of cat,drivability issues.They finaly changed the formulation and all is well now..But the damage was done.
I actually removed a few CEL bulbs from vehicals untill people could come up with $$$ to have cats replaced.That simulator sensor from URD sounds like a viable option instead of yanking CEL bulb.
I guess it dosen't matter what you decide to do.The damage is done to the cats and unless you fail emissions and can't register vehical.....Drive on,it wont hurt anything.
In my area of the country we had a problem when they decided to start reformulating fuel,This fuel was full of sulfur.Started seeing tons of cat,drivability issues.They finaly changed the formulation and all is well now..But the damage was done.
I actually removed a few CEL bulbs from vehicals untill people could come up with $$$ to have cats replaced.That simulator sensor from URD sounds like a viable option instead of yanking CEL bulb.
I guess it dosen't matter what you decide to do.The damage is done to the cats and unless you fail emissions and can't register vehical.....Drive on,it wont hurt anything.
03-11-2008, 07:11 AM
#14
To answer your question about the front or rear cat.It's probably both.If the sub2 is switching,basically it means that the cat(s) inbetween the front and rear sensors are not working(S1-S2).It would be possible that the front one went bad and if caught quick enough you could just replace that one,but once it goes the rear one gets overworked and then goes bad.
In my area of the country we had a problem when they decided to start reformulating fuel,This fuel was full of sulfur.Started seeing tons of cat,drivability issues.They finaly changed the formulation and all is well now..But the damage was done.
I actually removed a few CEL bulbs from vehicals untill people could come up with $$$ to have cats replaced.That simulator sensor from URD sounds like a viable option instead of yanking CEL bulb.
I guess it dosen't matter what you decide to do.The damage is done to the cats and unless you fail emissions and can't register vehical.....Drive on,it wont hurt anything.
In my area of the country we had a problem when they decided to start reformulating fuel,This fuel was full of sulfur.Started seeing tons of cat,drivability issues.They finaly changed the formulation and all is well now..But the damage was done.
I actually removed a few CEL bulbs from vehicals untill people could come up with $$$ to have cats replaced.That simulator sensor from URD sounds like a viable option instead of yanking CEL bulb.
I guess it dosen't matter what you decide to do.The damage is done to the cats and unless you fail emissions and can't register vehical.....Drive on,it wont hurt anything.
as long as the cat is not plugged
03-11-2008, 07:29 AM
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I realize what you are saying but what do you think those waveforms are created by? Fluctuating voltages... Most people don't have a $500 o-scope setting around to check O2 sensors with. It's not that critical of a measurement. Either the rear O2 is switching quickly or it's flat lined lean. I know your probably going by the toyota training manual description but you don't have to be that detailed to diagnose this problem. Sounds he's already identified the O2 as switching so the diagnosis is bad CAT.
you really don't want voltages. you want the waveforms.
the voltage you mention for b1s1 is fine. unlike an o2 sensor, that voltage is determined by the ECU anyway. but it is in range of normal
the voltage for the rear o2 sensor should be flat line basically. if it is spiking then yes maybe cat efficiency is gone
-
it is almost certain that you have a bad cat. if your sensor front or back was actually bad it is likely you'd be getting more codes than 0420. You also be getting 0125 and possibly others if the signals from the sensors were out of spec. if all you get is 0420 chances are the cat is used up
the voltage you mention for b1s1 is fine. unlike an o2 sensor, that voltage is determined by the ECU anyway. but it is in range of normal
the voltage for the rear o2 sensor should be flat line basically. if it is spiking then yes maybe cat efficiency is gone
-
it is almost certain that you have a bad cat. if your sensor front or back was actually bad it is likely you'd be getting more codes than 0420. You also be getting 0125 and possibly others if the signals from the sensors were out of spec. if all you get is 0420 chances are the cat is used up
03-11-2008, 08:03 AM
#16
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ALSO note, it is impossible to confirm A/F sensor voltage with any OBD II or Toyota scan tool, so don't
base any decisions on readings from b1 s1. it is basically a fixed value.
What you can determine, is an open or short. The ECU controls
the voltage, not the sensor itself. You are looking for either an open or short which a scan
tool can tell you, but the actual operation of the sensor cannot be determined.
base any decisions on readings from b1 s1. it is basically a fixed value.
What you can determine, is an open or short. The ECU controls
the voltage, not the sensor itself. You are looking for either an open or short which a scan
tool can tell you, but the actual operation of the sensor cannot be determined.
EDIT: Never mind, I get it--sort of. So what input does the ECU react to, if not the voltage? Current? And is there any A/F failure that is NOT an open or a short? (From the point of view of the ECU).
Last edited by TheDurk; 03-11-2008 at 08:17 AM.
03-11-2008, 09:43 AM
#17
A/F sensors are not your father's o2 sensors.
The A/F sensor is a wide ratio sensor.The A/F sensor Changes its current(amperage) output in relation to the amount of oxygen in the exhaust stream.
A detection circuit in the ECM detects the change and strength of current flow and puts out a voltage signal relatively proportional to exhaust oxygen content.
The A/F sensor is desighned so that at stoichiometry,there is no current flow and the voltage put out by the detection circuit is 3.3 volts.A rich mixture,which leaves very little oxygen in the exhaust stream,produces a negative current flow.The detection circuit will produce a voltage below 3.3 volts.A lean mixture,which has more oxygen in the exhaust stream.produces a positive current flow.The detection circuit will now produce a voltage signal above 3.3 volts.
With an A/F sensor,the ECM does not follow a rich lean cycle.
...............
P0125: related to output voltage.the A/f sensor is monitored for activity(voltage change) when; rpm 1500 or more,vehical speed 25-62 miles per hour,tps off idle,condition continues for 90 seconds,140 or more seconds have passed since engine was started,DTC is one trip code.
P1130,P1150: This monitor is concerened with A/F sensor voltage output.These DTC(s) are found if the output voltage remains fixed for a perdetermined period.Note:Voltage output changes take place inside the ECM.The diagnostic tester must be used for diagnosis.
P1133,P1153: The ECM monitors the A/F sensors responce characteristics.If the sensor responce rate deteriorates,a fault will be recorded.The responce rate cannot be confirmed by tests performed at the sensor.The responce rate calculation is a function of the ECM only.The ECM compares the A/F sensor's responce to the specifications stored in the ECM's programming.
P1135,P1155: All A/F sensors are monitored for abnormal heater condition.The ECM checks the amount of current required for the sensor heater.If the current is too high,or too low,a DTC will be set.If the current level is too high,the ECM will shut off the heater.When this happens,a P0125 can set..In early models,heater DTCs are two trip detection.Beginning with 2001 models,a phased change to one trip DTC detection began.
Note:When an A/F sensor DTC is found,it is important to look at each DTC description carefully before proceeding with diagnosis.In addtion to P0125,the A/F sensors each have three DTCs,one for a sensor range/performance malfunction,one for responce malfunction,and one for the sensor's heater circuit malfunction.Each DTC requires a different approach to diagnosis.
Also second generation A/F sensor(planar A/F sensor) is not interchangable with the older,cup element A/F sensor.
Heater resistance for the planer A/F sensor is slightly higher than the cup element A/F sensor(early).Heater resistance can be checked with DVOM (meter):.....
Diff in resistances for heater circuit in diff types of sensors...(heater temp at 68*F),ambient testing conditions=Planer A/F 1.8-3.4ohm;cup element A/F 0.8-1.4 ohm;02 sensor 11-16ohm.
The A/F sensor is a wide ratio sensor.The A/F sensor Changes its current(amperage) output in relation to the amount of oxygen in the exhaust stream.
A detection circuit in the ECM detects the change and strength of current flow and puts out a voltage signal relatively proportional to exhaust oxygen content.
The A/F sensor is desighned so that at stoichiometry,there is no current flow and the voltage put out by the detection circuit is 3.3 volts.A rich mixture,which leaves very little oxygen in the exhaust stream,produces a negative current flow.The detection circuit will produce a voltage below 3.3 volts.A lean mixture,which has more oxygen in the exhaust stream.produces a positive current flow.The detection circuit will now produce a voltage signal above 3.3 volts.
With an A/F sensor,the ECM does not follow a rich lean cycle.
...............
P0125: related to output voltage.the A/f sensor is monitored for activity(voltage change) when; rpm 1500 or more,vehical speed 25-62 miles per hour,tps off idle,condition continues for 90 seconds,140 or more seconds have passed since engine was started,DTC is one trip code.
P1130,P1150: This monitor is concerened with A/F sensor voltage output.These DTC(s) are found if the output voltage remains fixed for a perdetermined period.Note:Voltage output changes take place inside the ECM.The diagnostic tester must be used for diagnosis.
P1133,P1153: The ECM monitors the A/F sensors responce characteristics.If the sensor responce rate deteriorates,a fault will be recorded.The responce rate cannot be confirmed by tests performed at the sensor.The responce rate calculation is a function of the ECM only.The ECM compares the A/F sensor's responce to the specifications stored in the ECM's programming.
P1135,P1155: All A/F sensors are monitored for abnormal heater condition.The ECM checks the amount of current required for the sensor heater.If the current is too high,or too low,a DTC will be set.If the current level is too high,the ECM will shut off the heater.When this happens,a P0125 can set..In early models,heater DTCs are two trip detection.Beginning with 2001 models,a phased change to one trip DTC detection began.
Note:When an A/F sensor DTC is found,it is important to look at each DTC description carefully before proceeding with diagnosis.In addtion to P0125,the A/F sensors each have three DTCs,one for a sensor range/performance malfunction,one for responce malfunction,and one for the sensor's heater circuit malfunction.Each DTC requires a different approach to diagnosis.
Also second generation A/F sensor(planar A/F sensor) is not interchangable with the older,cup element A/F sensor.
Heater resistance for the planer A/F sensor is slightly higher than the cup element A/F sensor(early).Heater resistance can be checked with DVOM (meter):.....
Diff in resistances for heater circuit in diff types of sensors...(heater temp at 68*F),ambient testing conditions=Planer A/F 1.8-3.4ohm;cup element A/F 0.8-1.4 ohm;02 sensor 11-16ohm.
03-11-2008, 10:28 AM
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Thanks for the history lesson on AF sensors. It's good information for those who are not aware of the differences.
I'm not sure how we got off the subject of the p0420 but the fact is that you need to monitor the rear sensor, which is an O2, to determine the condition of your catalytic converter. switching = no good, flat lined = good.
Lets help this guy actually figure out what's wrong with his vehicle...
I'm not sure how we got off the subject of the p0420 but the fact is that you need to monitor the rear sensor, which is an O2, to determine the condition of your catalytic converter. switching = no good, flat lined = good.
Lets help this guy actually figure out what's wrong with his vehicle...
A/F sensors are not your father's o2 sensors.
The A/F sensor is a wide ratio sensor.The A/F sensor Changes its current(amperage) output in relation to the amount of oxygen in the exhaust stream.
A detection circuit in the ECM detects the change and strength of current flow and puts out a voltage signal relatively proportional to exhaust oxygen content.
The A/F sensor is desighned so that at stoichiometry,there is no current flow and the voltage put out by the detection circuit is 3.3 volts.A rich mixture,which leaves very little oxygen in the exhaust stream,produces a negative current flow.The detection circuit will produce a voltage below 3.3 volts.A lean mixture,which has more oxygen in the exhaust stream.produces a positive current flow.The detection circuit will now produce a voltage signal above 3.3 volts.
With an A/F sensor,the ECM does not follow a rich lean cycle.
...............
P0125: related to output voltage.the A/f sensor is monitored for activity(voltage change) when; rpm 1500 or more,vehical speed 25-62 miles per hour,tps off idle,condition continues for 90 seconds,140 or more seconds have passed since engine was started,DTC is one trip code.
P1130,P1150: This monitor is concerened with A/F sensor voltage output.These DTC(s) are found if the output voltage remains fixed for a perdetermined period.Note:Voltage output changes take place inside the ECM.The diagnostic tester must be used for diagnosis.
P1133,P1153: The ECM monitors the A/F sensors responce characteristics.If the sensor responce rate deteriorates,a fault will be recorded.The responce rate cannot be confirmed by tests performed at the sensor.The responce rate calculation is a function of the ECM only.The ECM compares the A/F sensor's responce to the specifications stored in the ECM's programming.
P1135,P1155: All A/F sensors are monitored for abnormal heater condition.The ECM checks the amount of current required for the sensor heater.If the current is too high,or too low,a DTC will be set.If the current level is too high,the ECM will shut off the heater.When this happens,a P0125 can set..In early models,heater DTCs are two trip detection.Beginning with 2001 models,a phased change to one trip DTC detection began.
Note:When an A/F sensor DTC is found,it is important to look at each DTC description carefully before proceeding with diagnosis.In addtion to P0125,the A/F sensors each have three DTCs,one for a sensor range/performance malfunction,one for responce malfunction,and one for the sensor's heater circuit malfunction.Each DTC requires a different approach to diagnosis.
Also second generation A/F sensor(planar A/F sensor) is not interchangable with the older,cup element A/F sensor.
Heater resistance for the planer A/F sensor is slightly higher than the cup element A/F sensor(early).Heater resistance can be checked with DVOM (meter):.....
Diff in resistances for heater circuit in diff types of sensors...(heater temp at 68*F),ambient testing conditions=Planer A/F 1.8-3.4ohm;cup element A/F 0.8-1.4 ohm;02 sensor 11-16ohm.
The A/F sensor is a wide ratio sensor.The A/F sensor Changes its current(amperage) output in relation to the amount of oxygen in the exhaust stream.
A detection circuit in the ECM detects the change and strength of current flow and puts out a voltage signal relatively proportional to exhaust oxygen content.
The A/F sensor is desighned so that at stoichiometry,there is no current flow and the voltage put out by the detection circuit is 3.3 volts.A rich mixture,which leaves very little oxygen in the exhaust stream,produces a negative current flow.The detection circuit will produce a voltage below 3.3 volts.A lean mixture,which has more oxygen in the exhaust stream.produces a positive current flow.The detection circuit will now produce a voltage signal above 3.3 volts.
With an A/F sensor,the ECM does not follow a rich lean cycle.
...............
P0125: related to output voltage.the A/f sensor is monitored for activity(voltage change) when; rpm 1500 or more,vehical speed 25-62 miles per hour,tps off idle,condition continues for 90 seconds,140 or more seconds have passed since engine was started,DTC is one trip code.
P1130,P1150: This monitor is concerened with A/F sensor voltage output.These DTC(s) are found if the output voltage remains fixed for a perdetermined period.Note:Voltage output changes take place inside the ECM.The diagnostic tester must be used for diagnosis.
P1133,P1153: The ECM monitors the A/F sensors responce characteristics.If the sensor responce rate deteriorates,a fault will be recorded.The responce rate cannot be confirmed by tests performed at the sensor.The responce rate calculation is a function of the ECM only.The ECM compares the A/F sensor's responce to the specifications stored in the ECM's programming.
P1135,P1155: All A/F sensors are monitored for abnormal heater condition.The ECM checks the amount of current required for the sensor heater.If the current is too high,or too low,a DTC will be set.If the current level is too high,the ECM will shut off the heater.When this happens,a P0125 can set..In early models,heater DTCs are two trip detection.Beginning with 2001 models,a phased change to one trip DTC detection began.
Note:When an A/F sensor DTC is found,it is important to look at each DTC description carefully before proceeding with diagnosis.In addtion to P0125,the A/F sensors each have three DTCs,one for a sensor range/performance malfunction,one for responce malfunction,and one for the sensor's heater circuit malfunction.Each DTC requires a different approach to diagnosis.
Also second generation A/F sensor(planar A/F sensor) is not interchangable with the older,cup element A/F sensor.
Heater resistance for the planer A/F sensor is slightly higher than the cup element A/F sensor(early).Heater resistance can be checked with DVOM (meter):.....
Diff in resistances for heater circuit in diff types of sensors...(heater temp at 68*F),ambient testing conditions=Planer A/F 1.8-3.4ohm;cup element A/F 0.8-1.4 ohm;02 sensor 11-16ohm.
03-11-2008, 03:04 PM
#20
Matt - from what I remember about your truck - you have over 100k miles. I think the warranty is 8 years or 80,000 miles? I seem to remember that.
I'm in the same boat as Matt but I have decided to spend $$ on replacing my sensors. My MPG wasn't as good so I was convinced my front A/F sensor was bad since I have over 120k on it. Well, replaced the A/F sensor and the CEL came back after 8 days. I have a new rear sensor ... going to swap that out this weekend.
I know this probably is a waste of $$ - but it makes me sick thinking I'd have to pay $1500 for CATs...I'm hoping something less expensive fixes this issue.
If it doesn't work (replacing the O2 sensor) - I'll think about he URD simulator. I'm just wondering how that will work once I trade the truck in/sell it. I don't know if that would become an issue if it was discovered after the vehicle was sold.. ?
I'm in the same boat as Matt but I have decided to spend $$ on replacing my sensors. My MPG wasn't as good so I was convinced my front A/F sensor was bad since I have over 120k on it. Well, replaced the A/F sensor and the CEL came back after 8 days. I have a new rear sensor ... going to swap that out this weekend.
I know this probably is a waste of $$ - but it makes me sick thinking I'd have to pay $1500 for CATs...I'm hoping something less expensive fixes this issue.
If it doesn't work (replacing the O2 sensor) - I'll think about he URD simulator. I'm just wondering how that will work once I trade the truck in/sell it. I don't know if that would become an issue if it was discovered after the vehicle was sold.. ?
