hey guys i just bought an ALDL cable and read whats going on with my laptop. i have been having an issue where my SES light comes on at idle only after the car has warmed up. it says code 22 low voltage to the tps, ive checked the tps and at closed throttle its at 0.55 so i know its not showing low voltage. any ideas on what else it could be? its a 2.8L 87 firebird...

 

Did the light come back on while the scanner was showing 0.55v?

 

The light only comes on when the car is warm at idle, like at a stop light. When i checked the voltage with my scanner the engine was not on, i just had the key turned on for electricity so i could get the voltage reading of the tps which said 0.55 at closed throttle

 

So now what you have to do is have someone running the scanner while you are driving, engine warm and have him watch what happens when the problem actually occurs.

btw, it was me you were talking to at Red Devil River helping you get the cable set up.

Problems that don't occur all the time are harder to troubleshoot. You have been blessed with one of these occurrences. It might take a few tries to finally see what is happening but if you can re-create the problem you should be able to troubleshoot it.

I can't come up with any scenario that would cause a low volt on the TPS sensor only when the engine is warm and only at idle. If indeed you are seeing this happen with the scanner when the engine is warm, and only at idle, what I would do next is backprobe the gray wire - which should always have +5v on it and see if the +5v also drops when the return voltage drops when the problem happens. If the 5v is dropping then you have to chase the problem that way. If the 5v stays solid, but TunerPro RT is showing the TPS voltage dropping, then you need to troubleshoot a problem with the Dk. Blue wire.

http://www.enduringautomotive.com/ho...robe-a-sensor/

Finally - be safe. Don't crash your car by trying to run TunerPro RT while you are driving. Have someone watch the scanner/meter for you while you drive, or vice versa.

Let us know what you find is the problem.

 

great man thanks for all the info on the phone it was great. well i took the car out for a drive with the scanner plugged in. when i was decelerating from normal driving speed the tps showed the voltage drop to 0.20 and the SES light came on but then turned off after pressing the gas pedal. so what does that mean? and also tunerPro is showing an error next to code 34. do these two codes have anything to do with each other? i changed the MAF and the MAF relay i thought i fixed the code 34 problem but now its back... im totally frustrated and stumped and i need this car fixed and reliable its my everyday driver right now!!

 

Ok - I hear you that the fact that your problem is still existing is frustrating. The good news is that you are closer to solving the problem. The thing is however is this is like a long line at a theme park, and you just got to the end of one waiting area just to turn the corner and find a second long line waiting area.

Looking at the wiring for your ECM I see the wires for the MAF and TPS are on different connectors.



That eliminates a loose connector causing both problems at once.

Check for damage on your wiring harness. It runs from the engine, through the passengers fender and then to kick panel on the right and then to the ECM under the passengers side of the dash. I wouldn't take things apart to look for damage but just look and feel where you can. Damage to the harness isn't very likely but always a possibility.

What are your thoughts of back probing the TPS connector? You can also probe the at the ECM if that makes things simpler.

I would try swapping the ECM. You can get a used one on ebay for not too much. Your ECM for a 87 Firebird 2.8 is a 1227302. You will have to swap the PROM from your ECM into the replacement ECM. It is pretty much impossible for the PROM to be causing the problem.

http://www.ebay.com/sch/i.html?_trks...at=0&_from=R40

The TPS voltage dropping to 0.20 clearly is what is causing your Code 22. The TPS voltage could be dropping because the signal return wire - Dk Blue - is opening up or shorting to ground. It could also be caused by the +5v, supplied by the ECM to the TPS on the Gray wire is also either opening up, shorting to ground, or that perhaps the ECM isn't sending the +5v out.

So here is something to look at.

The TPS should give you are response between about 0.5v at rest to 4.5v at WOT. When this problem was happening the voltage dropped to about 0.2 at rest. Did the entire voltage range move or did only the at rest voltage move? It is a subjective question but perhaps you can determine it.

If the entire range slipped down, then the problem is only showing up at deceleration only because the throttle is closed and the range is slipped. If however the range is good all the time except at deceleration that would be something different. Not sure exactly what to look with it but it might be a clue to figuring this problem out.

How does the connector that plugs into your TPS look? Are the metal terminals inside the connector corroded? That could be causing the Code 22.

http://www.ebay.com/itm/Throttle-Position-Sensor-TPS-TP-Connector-Pigtail-Harness-85-92-TPI-TBI-GM-/300875132294?pt=Motors_Car_Truck_Parts_Accessories&hash=item460d8e2d86&vxp=mtr
If you do replace the TPS connector the wires must be soldered and shrink tubed. If you don't solder them expect them to fail. Crimps fail all the time.