I'll keep it short and to the point so here it goes....

Keep in mind that i never heard this truck run before last night when i got it running so i have no idea what it used to run like.


Ok its a 1994 Gmc S15 Jimmy, 4.3 vin W, 4x4 and i had to change the FPR and the fuel leak problem is fixed. It runs rough but smooths out after it idles for a min or two. When you tap the throttle it revs up but sounds like it has a miss but not real bad though then when it comes back down it about dies then comes back to normal. It almost sounds like a big cam.

I checked the OBD1 codes and they are as follows:

DTC 22 Throttle Position Sensor error ( signal low)

DTC 34 MAP Sensor circuit error ( signal low indicating high vaccum)

Is there any adjustment on the TPS on these to get the signal up where it needs to be or just change it? Does the code 34 mean the MAP is bad or possible plenum leak? I couldn't see the plenum leaking b/c i used a new gasket and cleaned the crap out of both gasket surfaces but i guess its possible.


I appreciate any help possible thanks.

 

Since both of those sensors are powered off of the same 5V reference from the ECU, I would check to make sure that they are getting the full 5V from the ECU and that they both have good grounds. If either of those two things is messed up, it will trigger those codes.

 

just check it at the plugs?

 

Yes. Key-on, there should be 5V on one of the wires and a good ground on another one of them (I do not have the pin-outs in front of me so I'm shooting from the hip here). Ohm out the ground. It should be quite low. You can also ohm out the wire from the sensor back to the ECU. While you have the multimeter connected, move the harness around to check for the possibility of broken/damaged wiring inside the harness.

 

Ok, I'll check out the voltage and wires and post the results. If you could get the pin outs or tell me how to find them that would be awesome! No super big hurry though. Thanks

 

I checked the volts going to the TPS and MAP and they are as follows:


TPS-10.70 volts

MAP-4.72 volts

haven't checked ohms yet. it seems to be getting proper power to the MAP sensor but not sure about the TPS. Any ideas anyone?


Thanks,


Dustin

 

Here are the schematics for both the TPS and MAP sensor (see attached). Both show 5V reference from the PCM. Sounds like the TPS wiring is either shorted out somewhere or the PCM has somehow failed and is pushing 12V to the TPS sensor.

 

Thanks for the schematics. I feel like an idiot b/c i tested a sensor that was not the TPS. i went back out and tested the TPS and i got 4.98 volts. LOL

 

Just wondering, where is the pcm located on this jimmy?

Thanks to all for all help.

 

Under the dash near the glove box.