Jeep Repair Problems? Ask a Mechanic for Answers ASAP
Hello and welcome to Just Answer!
It sounds like the PCM has failed or you have a power/ground issue to the PCM. The PCM controls the cooling fan, asd relay and purge solenoid. If the power and grounds check ok and you still have no communication to the PCM, you will need a PCM.
The first thing I would do is check all your power and grounds to the PCM. Do you have a wiring schematic or would you like me to send the PCM pinout?
I have PCM pinout. I have voltage at the ASD relay (from the PCM). Could the PCM still be bad if I have power there? Also,will the vehicle run with the ASD bypassed if the PCM is bad? What pwer and ground checks at the PCM I you suggesting to check?
You think the Crankshaft sensor is ok?
The ASD relay should have power at all times on one terminal, the PCM just controls the relay coil. When you first turn the key on, the PCM will energize the relay for a couple seconds and then turn it off. When you start cranking the engine and the PCM sees a valid crank position signal, the PCM will re-energize the relay.
Here is what I need you to check for power and grounds.
In the C1 PCM connector(black), I need you to check terminal #2(orange-blue wire) for key on power.
Terminal #22(red-black) for battery power. Terminal #31(black-white) & 32(black-tan) for ground. Check these and let me know!
Thanks again for the help with this. With the black connector removed from the PCM, I have 12v ignition at #2 , ground at # XXXXX and 32, nothing at # XXXXX I ohmed # XXXXX and it is not shorted to ground.
I do have 12v at the ASD relay terminal #30. With the relay removed and I ohm out #30 to #22 on the black connector, it is open.
Sorry I didn't get back to you sooner, My son had a hockey game.
Can I get you to check fuse # XXXXX(10 amp) in the fuse box in the engine compartment? The power is fed to the PCM through this fuse.
I understand about other commitments.This is my daughters Jeep and I am trying to work on this and have several other things going on also.
All the fuses in the engine compartment are ok. I haven't checked any inside the vehicle.
So far, with what we have done, do you suspect anything?
If this helps your diagnosis, with ignition on, the fuel and voltage gauge won't work,and at one point, the fan was running but seemed to be sluggish,so I tapped on the fuse/relay box and the fan changed rpm. I removed the bottom tray of the relay/fuse box to check for corrision or bad wiring,however it all looked good.
I made a mistake on a couple things, I thought we were working on a Grand Cherokee
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dark green-black, not red-black and the fuse should be #22(15 amp) If you don't have power to terminal #22 at all times we will have to see if fuse # XXXXX has power to it. Can you check both sides of the fuse and see if you have power to both sides? Leave the fuse in and see if you have power to both sides.
There isn't 12v on both sides of the fuse. I turned the fuse/relay center over and there isn't 12v at the green-black terminal.
Is there other things I can check or do you have an idea of what may be the problem.
I am out of town tomorrow for two weeks and would like to at least get a diagnosis of the problem. Hopefully we can resolve it today, depending on your availability.
Thanks again for your help.
The fuse was burnt. They were the first thigs I checked when all this started. ?? Maybe I had my finger on the Multimeter lead ..... it was very cold out at the time. I replaced the fuse and the fan isn't running now and the relays aren't chattering.
I have to reinstall the CKS before I attempt to start it though, and it is a pain to get in that area.
do you think this was the problem all along then?
Yes, I think that was likely the problem all along. The PCM can do funny things when it's missing a power or ground. Let me know how you make out!
I will get back with you later on today, and if it doesn't start or it happens again, I will try and get back with you in a couple weeks when I return. regardless of that I will accept the answer this afternoon so you can be compensated. ( I think thats how it works)
Thank you very much! If you have anymore problems, just reply back and I will get back to you asap! Good luck!!
That's great, I am glad I was able to help you! If you ever need help in the future, feel free to contact me again.
Take care and thank you very much!