flatbed

89 22re 4x4 M/T
Trying to check connection from o2 sensor to rest of truck. Have been getting codes 25/26 rich and lean and 13mpg. Owner before me hacked and spliced. Put in a new o2 sensor and code 21 went away but 25/26 still come on and off.

-What wire would control the signal to ecm? ox1? B+?
-Does the black wire actually heat up the o2 sensor?
-What does B+ do?
-Is pink/green wire ground?
-Brow is spliced tp brown and black, just grounds maybe?

In the middle of cross country road trip and need to fix before we head back home with 13mpg!!

alltracman78

I don't have a wiring manual for the 89, so this is general Toyota wiring info, but it SHOULD be correct.

The O2 sensor creates the signal, and sends it to the ECU via the Ox1 wire.
The O2 sensor heater gets power from a generic power wire [key on power], the ECU provides the ground to the circuit [HT pin at the ECU].
B+ is switched on power from the EFI fuse, basically key on power.
Don't know
Brown and white/black are usually grounds, black is not.

If you have hacked up/questionable wiring you're best off forgetting about the DIAG box signals for now and checking directly at the ECU. This way you see what the ECU sees [in case the wiring to the DIAG box is bad].
Honestly, to check the O2 signal the easiest thing to do is buy a cheap A:F gauge and hook it up. This will give you the same signal the ECU sees and is easier than trying to read it from a digital mulitimeter [it changes too fast for the display].

The other thing you can do is check the VF signal. This will show you ROUGH fuel trim [how much fuel the ECU is adding or subtracting from the base fuel maps].
Check this with the engine running, ideally driving around, because the fuel trim changes as you drive.
Take the positive lead from the multimeter and hook it to the VF signal wire, and the negative to E1 [or any good ground]. Make sure you don't have TE1 [or T1/T] grounded, this will give you a different signal.
You'll have 1 of 3 readings; 0V, 2.5V or 5V [you may also get 1.25V or 3.75V but I don't think your ECU has that much resolution].
0V means the ECU thinks the engine is running rich, so it's taking away fuel [negative fuel trim].
2.5V means it's right on target.
5V means it thinks the engine is running lean so it's adding fuel [positive fuel trim].
1.25V is negative, just not as much as 0V.
3.75V is positive, just not as much as 5V.

Remember, this is a rough reading. Your ECU isn't super accurate.
This will hopefully give you a rough ballpark of your problem.
If the trim is positive it's adding fuel, so you're running lean. For example a vacuum leak, or dirty injectors.
Negative trim means your running rich, for example leaking CSI.

Don't forget that the ECU is stupid and can only go by what the sensors tell it.
So if the engine isn't completely combusting the fuel/air mix the O2 is going to tell the ECU it's lean and will cause a positive fuel trim.

Sorry for the rambling, it's late and I'm trying to get sleepy.

flatbed

Thanks for the quick response and great info!!
Tried to find VF pin on ECU with no luck. Found VF1 on DIAG box, could be same?

Also main concern is voltage from O2 sensor. I measured 0.00v from black double insulated wire from O2 sensor (also blue on O2 sensor harness) after warm up and running at 2500rpm. Twice in 10minutes it jumped around from .2v-.8v for 3sec then back to 0.00v. Double insulated black wire from blue is the siganl wire correct? Is this normal or should it always jump from .3-.7?

Red/Wht B+ is putting out 13v.
Pink/Grn is grounding.
Brown is grounding

Toyota tech at local shop said it should have two O2 sensors even if it isn't a CA model???

alltracman78

Yup, VF1 is the same wire, it comes directly from the ECU.
You can check the signal at the DIAG box, I just suggested the ECU pin because it's pretty much guaranteed to not be hacked there. It will be the same color as the wire at the DIAG box [purple maybe?].

If you can't find in in pinouts, if you remove the top cover of the ECU the pinouts SHOULD be printed on the circuit board at the connectors.

If the ECU isn't getting an O2 signal it's going to run rich. No question there.
It should always jump from ~ .3 - .7V. Unless the engine is in cold start or WOT. Then it should be a steady close to 1.0V. You should never see 0V.
It isn't actually a double insulated wire, it's a wire covered with shielding [steel braid].

Make sure the heater is working first [you should have 12V at the heater V supply wire and 0V at the heater ground wire [both measured at the sensor].
If the heater is working, check the signal at the sensor. You should have that switching voltage you mentioned. But, if the ECU isn't getting the O2 signal it's going to run rich, so you may get that steady .8V reading.

If you're getting a good reading at the sensor, check at the ECU. If you have problems there you know the wiring is bad somewhere in between.

I don't know specifically on your truck, but I wouldn't think a Federal Emissions 88 would have a second sensor behind the cat. However I'm not going to tell you it doesn't.
If you are supposed to, it should be a 2 wire O2 sensor after the cat.
You could always go to a Toyota parts dep with your VIN and have them take a look at the exhaust diagram, it should show if you're supposed to have 1 or 2.

noglu10

I have a 90 pickup with 22re and A/T. Getting solid 21 error code with a CEL. I replaced the sensor but still getting error. I uplugged the connectors from the efi computer. I metered all four wires. I get continuity from the black and brown wires to the ECU. I get continuity from the red/white wire to the ECU. I don't get continuity from the pink/green wire to the ECU. I don't have a wiring diagram. What is the pink/green wire for and does it go anywhere else but from the sensor harness to the ECU. It is hard to trace the harness because it goes over the tranny and I have not been able to remove it to check it for a broken wire.

Tom

scope103

Brown is ground (so your continuity is just checking that one of the ECU grounds eventually connects to the sensor ground, but that's good enough). Black is the shielded signal wire. White/Red is the B+ (power to heater) line. And Red/Green is grounded at the ECU to turn on the heater. If Red/Green at the sensor connector does not get through to Red/Green (pin 22) on the ECU, the sensor heater will not turn on. More importantly, the open on pin 22 throws code 21.

So your Red/Green wire is broken. Replace it (or if you're lazy, just run a separate wire) and you should be back up.

noglu10

Thanks for the reply. I'm pretty sure the circuit is open somewhere. I concur with running a parallel wire to see if the error goes away. If so I will attempt to find and repair the break. Thanks again.

flatbed

My problem was a burn in the wires where they get close to the exhaust, just before o2 wires join the main harness at transmission signal wires. Make sure it is oem harness, could have been spliced for universal o2 sensor at some point and lost continuity. Pink/Green should go straight to ecu.

noglu10

Pink/green wire broken near oil filter. Repaired. It was a major PITA getting arms and hands to where I could work on the splice. Ended up taking off front right wheel and using access through the wheel well. Still got lots of scratches and scrapes on my arms and hands. Damage to wire harness may have been the result of a rodent or squirrel while I was on vacation a couple of weeks ago. Felt good to trouble shoot the problem using diagrams and a meter. Thanks again for the info.

Tom