No Start, guages dead

I have a 94 xj 4.0 HO. Started having no start problems. Needed jump start, found alt bad, replaced. Everything fine for a few months. Then started again with no start. Found CPS bad and replaced with NAPA cps. Again ran fine couple months. Now no start, no guages move with key on or check engine light. Did usual check all relays, fuses, check PCM for batt volts in, found wire from PCM to mil light and powered with power probe, lamp turned on on dash. Have 5v on wire 6 and 9v on wire 7. Have batt volts on wire 9 with key on. Could PCM be bad? What else do I need to check?
Thank you for any info.

Could be bad PCM. Dumb question, did you disco the battery and clean the posts / cables?

Yes, cleaned batt post and cables. Then replaced cables with new #1 size cables to body grounds and positive cable to starter, replaced battery with new battery. Still same, spins over, not fire up.

I may be wrong, as I'm least experienced with the obdI HO chassis, but aren't the gauges still wired directly to senders and not run through the PCM?

if that's the case it sounds like you have a chassis wiring issue. Have you chcked for voltage at the interior fuse panel for the gauges? Checked the relays/fuses underhood? Checked the ignition switch?

Check the CPS with a meter. Could have gotten a bad one. Maybe not but it's worth checking.

Ignition switch under the dash column? It has known to cause no gauge scenarios.

When I get no MIL light I start by unplugging sensors. Turn the key to the run position ever time you unplug a sensor and see if it lights up.

They bundle the supply voltage to various sensors in different ways depending on the year, but I'd start by unplugging the CPS, then the sync sensor and then (maybe) the engine temp sensor on the thermostat housing.

If you test for supply voltage at the CPS do it with the connector connected. The CPS can short internally and it may not show up with the standard CPS ohm test.


All your gauges being dead is worrisome. I doubt the PCM controls all the gauges on the 94.

I'll have to search through the FSM on the 94 (if I have one), but the usually setup is one power wire to the PCM is from the ignition switch and basically just turns on the PCM. The other power wire comes directly from the PDC and is the main power. The PCM is usually my last choice when troubleshooting, other than the regulator function for the alternator, it rarely fails. Grounds are always to be suspect. The grounds next to the PCM on the inner fender well, are often overlooked, as is the main ground from the block to the firewall.