I am trying to diagnose a no buss message . I have eliminated all sensors and cleaned as many grounds as i can find. I had my voltmeter out and was checking ground voltage and 5v reference. i put my ground probe in the wrong pin o my harness and got 6.2 v. Is this a power to ground short i have checked relays and sensors but i must be missing something or have a wire short or a pcm short. I have checked and replaced for good measure the crank position sensor, tested the cam position sensor. coolant temp sensor, intake temp sensor, iac, tps, mass airflow sensor. can anyone provide any help on what other sensors could be shorting or a common place for wire shorts.

 

First of all what kind of Jeep are you talking about? Also year an engine. They are all not the same.

 

sorry 01 xj 4.0

 

I sauppose you could check for voltages at the CPS connector (disconnected) a different way than what you describe.

Turn ignition switch to RUN, without starting the engine.

Using your Voltmeter, touch the pin cavity of the CPS body harness connector with the Orange wire, and the meter (-) probe to engine as a ground. You should see around 5 +/- .5 Volts. 6.2 Volts would be too high.

Touch the pin cavity with the Brown/Yellow tracer wire. You should see around .016 +/- Volts. This is the ground circuit for all the sensors. There will be a low Voltage present here as long as the key is to RUN, and zero Voltage with the key to OFF. If you are seeing 6.2 Volts here, there is a short to power somewhere.

If you are seeing above 5.5 Volts at the Orange wire, try checking at the TPS and Map sensors as well. The Orange wire is the 5 Volt reference for the engine management sensors. If they too are above 5.5 Volts I would suspect battery voltage leakng accross to the PCM through the clockspring (via the cruise control circuit and horn relay). Or the PCM has a defect causing this.

If you are, in fact, seeing above 5.5 Volts at the sensors, remove the cover from the Junction Block and remove the horn relay (the middle of the three relays), then recheck the voltages. If they return to 5 +/- .5 Volts it's the clockspring. If they don't return to normal Voltage, the problem lies elsewhere.

 

My voltage at the cps ( i have a 3 wire) are both 5.2 and my ground is 0.13v batt is around 11.7v. when i hook the negative probe of my volt meter to a 12v power source ( to test for clean grounds) and put the positive probe in a power wire ( i did it on accident) i get 6.2 volts does that indicate anything or is it just because i am a retard.