The Knock Sensor from Hell
11-04-2014, 03:36 PM
#21
I believe Scope mentioned in this thread before... but here it is again fyi zombie. When the ecu doesnt get a good signal from the knock sensor, it shows the check engine light and retards the timing. The resulting power loss and fuel guzzling is ridiculous. This is to save the engine from potential damage.
11-04-2014, 03:37 PM
#22
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Yep, we have done the external knock sensor several times with several sensors. I did it yesterday, using the 1990 sensors (2 different ones) and both still returned the 52 code.
11-04-2014, 05:09 PM
#23
Sorry for making this part for my education, but every time this code is detected, it makes the ignition retard and guzzle gas? Is that what's been going on besides not passing inspection due to a check engine light? I'm sorry if it's been painful to suggest before that this vehicle just needs to be parted out or something, unless that different year ECU changes the state of things, or unless the engine in the other truck is satisfactory.
Last edited by zombie_stomp; 11-04-2014 at 05:12 PM.
11-06-2014, 08:48 PM
#24
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The knock sensor only picks up a specific frequency which is equal to a ping.
The ECU detects a impedance reading to know its there.
The only thing the ECU (OBD1) will do is retard timing or go limp mode when not detected at all, Other then that, Nothing.
The ECU detects a impedance reading to know its there.
The only thing the ECU (OBD1) will do is retard timing or go limp mode when not detected at all, Other then that, Nothing.
11-07-2014, 06:58 AM
#25
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I don't think that's how it works. First, the explanation of code 52 is "With engine speed between 1,600 rpm – 5,200 rpm, signal from knock sensor is not input to ECM for 6 revolution. (KNK)."
Second, the knock sensor is a piezo sensor, which should have infinite impedance at rest.
Third, if the ECU detected the sensor by impedance alone, you know that someone would have "bypassed" his knock sensor with a resistor.
I'm pretty sure the ECU is listening for the signal from the sensor, and when that's gone (for 6 revolutions), it throws the code. I don't think impedance has anything to do with it.
Second, the knock sensor is a piezo sensor, which should have infinite impedance at rest.
Third, if the ECU detected the sensor by impedance alone, you know that someone would have "bypassed" his knock sensor with a resistor.
I'm pretty sure the ECU is listening for the signal from the sensor, and when that's gone (for 6 revolutions), it throws the code. I don't think impedance has anything to do with it.
01-04-2015, 10:00 AM
#26
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the end of mine broke but hasn,t thrown check engine light, pushed the end back together and epoxied it hope it works. not sure what it is for but will look for another one at wrecking yard. over 200.00 is ridiculus for a new one, excuse the spelling
01-06-2015, 08:23 AM
#27
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I don't think that's how it works. First, the explanation of code 52 is "With engine speed between 1,600 rpm – 5,200 rpm, signal from knock sensor is not input to ECM for 6 revolution. (KNK)."
Second, the knock sensor is a piezo sensor, which should have infinite impedance at rest.
Third, if the ECU detected the sensor by impedance alone, you know that someone would have "bypassed" his knock sensor with a resistor.
I'm pretty sure the ECU is listening for the signal from the sensor, and when that's gone (for 6 revolutions), it throws the code. I don't think impedance has anything to do with it.
Second, the knock sensor is a piezo sensor, which should have infinite impedance at rest.
Third, if the ECU detected the sensor by impedance alone, you know that someone would have "bypassed" his knock sensor with a resistor.
I'm pretty sure the ECU is listening for the signal from the sensor, and when that's gone (for 6 revolutions), it throws the code. I don't think impedance has anything to do with it.
The link in my signature below has pictures I uploaded of the Toyota manual regarding the Knock Circuit.
01-16-2015, 04:34 AM
#29
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When the Knock Circuit functions properly, it's 100% invisible to the end user. When it does not function properly, code 52 is set.
The problem exists somewhere between:
ECU (not common)
Sensor (reasonably common at this age, replace with OEM, not parts store junk!)
Wiring (most common)
01-16-2015, 08:39 AM
#31
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As Schaeff says, code 52 appears when there is NO signal from the knock sensor.
01-16-2015, 10:32 AM
#32
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My peabrain tells me if the piezo device from Radio Shack gets rid of the cel, everything to the sensor is good. After reading this I can't remember, did you use a factory knock sensor? If not I would.
01-16-2015, 12:55 PM
#33
I would be really surprised if Fords work this way, but we know Toyotas do not. A rattling bracket wouldn't produce the right frequency to do anything. But even if it did, "too many" knock detected signals would only retard timing, not throw a code.
As Schaeff says, code 52 appears when there is NO signal from the knock sensor.
As Schaeff says, code 52 appears when there is NO signal from the knock sensor.
06-24-2018, 03:28 PM
#34
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Code 52
Ok, here's the latest on the Knock Sensor from Hell:
1) We double checked ground connections. We added additional grounding/bonding straps just for fun. This sucker is grounded. This made no difference whatsoever.
2)Researched the grounding at the knock sensor issue. Gevo and Scope you were correct. It as absolutely NOT grounded at the sensor. The pig tail is two pole and reduces to one pole right before the sensor connects to a one pole plug. The shield is just flying and taped/heat shrunk at the factory. I stand corrected.
3) Tried mounting the knock sensor outside of the engine again. Same result. Check Engine. Code 52.
4) My son did some more Googling and found a guy somewhere with a similar problem with a knock sensor on a Honda. The Honda guy solved it by buying a piezo transducer at Radio Shack (part #273-0073) and installing it in place of the knock sensor. I'll be damned if it didn't work! No more "check engine" light, no more code 52.
I understand that we currently do not have any anti-knock protection, but on the flip side, we also do not have a check-engine light and we can get the stupid thing smogged.
It only took two years. Technically, we still have not solved the problem, but we have treated the symptom and for the time being we're calling it a victory. I'm hoping that the check engine light stays off long enough to just get past the smog test.
What a PIA.
1) We double checked ground connections. We added additional grounding/bonding straps just for fun. This sucker is grounded. This made no difference whatsoever.
2)Researched the grounding at the knock sensor issue. Gevo and Scope you were correct. It as absolutely NOT grounded at the sensor. The pig tail is two pole and reduces to one pole right before the sensor connects to a one pole plug. The shield is just flying and taped/heat shrunk at the factory. I stand corrected.
3) Tried mounting the knock sensor outside of the engine again. Same result. Check Engine. Code 52.
4) My son did some more Googling and found a guy somewhere with a similar problem with a knock sensor on a Honda. The Honda guy solved it by buying a piezo transducer at Radio Shack (part #273-0073) and installing it in place of the knock sensor. I'll be damned if it didn't work! No more "check engine" light, no more code 52.
I understand that we currently do not have any anti-knock protection, but on the flip side, we also do not have a check-engine light and we can get the stupid thing smogged.
It only took two years. Technically, we still have not solved the problem, but we have treated the symptom and for the time being we're calling it a victory. I'm hoping that the check engine light stays off long enough to just get past the smog test.
What a PIA.
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