Hey guys I need help. I have a 5.9 swapped in my 98 TJ. I drove it about 1000 miles with a 5.2 PCM with no real problems once I started driving it. I recently got a5.9 PCM and drove it a few times, then a few days later it would not start. Here is what I have. I have 5V to the CKP CPS MAF and TPS from the primary wire. I also have 5V to all of the sensors from the PCM on the sensor wires on all of the same sensors. I had 2V coming from the VSS sensor with the supply wire disconnected from the PCM. I disconnected the transmission connector and the 2V goes away so I know there is a problem inside the transmission. I get fuel and 12V to coil when the key is turned on and 9.7V while cranking. I believe that I have a bad PCM. I temp installed my 5.2 PCM and it does the same things. Recent CKP replacement with a Mopar one. O2 sensors connected or disconnected has no effect on systoms. Any help will be appreciated!!!!

 

Same symptoms with 2 different PCMs? Not likely PCM issue then. DO you have wiring diagrams?

 

i read this story, didnt do it my self. after having the engine shout off again again. he found that the computer had a tab with a wire soldered to it. the tab was steel regular solder doesnt stick to steel very good. by using silver solder the trouble was gone hope that helps.

 

Make sure you are getting a good ground to the coil. It receives a constant power but spark is controlled by pcm intercepting the coils ground.

 

Does this not seem way too low?

 

do you have spark at the plugs?
do you have steady fuel pressure when cranking the starter? (not just at initial ignition on).

have you tried spraying starting fluid down the throttle body? does that have any effect?

 

Yeah.....

I cannot read through long stuff with no line spacing at my old age. I saw the first part of the post, and the last. But this could be an issue!

 

Hey, I admit to having needed to read it 3x to pick up on it. I'm certainly not saying it is a culprit as I've not had the need to check the voltage during cranking, but it just stands out like a sore thumb to me.

Of course, the root cause(s) could be indirectly related to this....given the context of this tech query.