b17gsr

Hi all,

New here after recently picking up a non starting XJ as a project vehicle for my son. Here’s the debugging we’ve done to date (won’t bore you with things corrected to get to this point...):

1. When turn ignition key to run, fuel pump does not prime.
2. Checked fuses in PDC, look and test ok.
3. Moved relays around (I know starter relay is good), and still no fuel priming when ignition in run position. I can feel the starter relay clicking (any relay In that socket while cranking), but can’t feel any relay click at the fuel pump socket.
4. With fuel pump relay removed, if I short out pins 2 & 8, fuel pump works and there’s good fuel pressure at the rail (don’t have pressure tester, so cannot confirm exact fuel pressure).
5. Battery power present on pin 4 when we turn the ignition to run & crank.
6. Checked continuity of pin 6 back to the PCM. All good.

Since the fuel pump won’t prime when the key is turned to run position, I’m suspecting that the PCM is faulty. Is there anything else I should check before going to the local wrecker and pulling a PCM? I did check all the fuses in PDC, but forgot to check if all fuses in the Junction Block are ok, other than fuse 11 (it was good). Are there any fuses in the Junction Box that could prevent the PCM from grounding pin 6 for the fuel pump relay to latch?

I did notice that one of the wires to the upstream O2 sensor was melted, so I repaired it and re-routed the harness. Fuse in PDC is good.

Thanks

b17gsr

After reading another thread, figured I should check the CPS. Read infinite between pins A-B, B-C and C-A (not only at 20k ohm, but even at 2,000k ohm). Does that make sense?

b17gsr

With CPS plugged or unplugged, the only gauge that moves with ignition turned to run is the oil pressure and odometer displays. Complete cluster seems to work when doing the self diagnostic test.

Pulled code 1694. Started testing the PCM. At the DTC, read 2.41V between pins 3 - 5 and 11 - 5 with ignition set to run. With ignition in lock position and negative battery terminal disconnected, resistance between pins 3 and 11 was 59.9 ohms.

Will have to continue troubleshooting when time and weather permit.

b17gsr

With more than 12V at the battery and ignition to run, voltage to ground at CPS orange wire is 0.5V,..

time to find a used PCM.

b17gsr

This problem is fixed. Faulty PCM replaced and all issues resolved.

timesx2

b17gsr I've got the same problem per say so from reading your post I figure that the pcm was not sending the ground for the relay??? I bought this 98 xj and replaced the wiring loom under the hood entire and not only the fuel pump but a lot of electrical ploblems… any help on this manner that you can think of the asd doesn't have a ground also they have fuse power and key power but no ground from the pcm

b17gsr

Are you also having voltage issues on the bus with the sensors unplugged?

if yes, I recommend trying a replacement PCM.

good luck!

snagster123

How did you test the ground/power at the CPS (I assume you mean Crank Pos Sensor)? how did you understand that 0.5V was not accurate? How is this related to the Powertrain Control Module (PCM)?