Oh. That's why we like to be able to see what the PCM is reading on these sensor inputs. What happens at the TPS ref voltages if you disconnect the jumper at the MAP harness?


George

 

Engine running and Fused jumper across map 5v ref and map sensor output- 0v across 5v ref and return, same for tps

Engine running fused jumper disconnected- 5v across 5v ref and return, same for tps

For some reason when that fused jumper is connected is dropping power to tps and map

 

This leaves the ECM in play. Did you ever test the disconnected MAP sensor input for resistance to ground?

George

 

Input to the ecm that is.

George

 

I have open loop across sensor output to ground with map disconnected

 

What are your resistance measurements going into the ecm from sensor input to ground with the sensors disconnected for both the MAP and TPS? I am trying to see of your MAP senor input is fried in the ECM by comparing the input impedance vales, assuming that the circuits are the same.

George

 

Key off both sensors unplugged 212 k ohms on the tps and open loop on the map

 

The MAP sensor input on the ECM reads infinite resistance (OL), not shorted to ground? Apparently its open with no power and shorted to ground under power which is why it pulls down the +5V ref voltage

The problem is that I do not know what the input circuit is in the ECM for these two sensors and proper input impedance measurements are more complicated than this. We are just doing a crude test.. I had you check them both on the assumption that they are the same input circuit since they both receive an analog 1-5v signal. If that's true then it looks like your ECM may be bad. Its odd however that the MAP sensor wire is shorted to ground AND the input to the ECM is bad. Inputting ground to an amplifier input should not destroy it. The other problem is that if I am wrong and the imputs are different, the MAP resistance reading would be different. Was your DVM on the highest ohm range?

George

 

If this rain will stop I will go out to my 2002 and measure the input resistance at the ECM of my MAP sensor input and see what I get.

George

 

Since my computer may have a different circuit, if anyone with a '95 is reading this thread can you measure your resistance to ground of the signal wire to the ECM for the MAP sensor with the MAP sensor unplugged with key on engine off?

George