ECU affecting Instrument cluster?


New Member
Jan 29, 2023
My 1998 TJ Sport has very few lights (illumination lamps) on the cluster working, the brake lamp does not work, the turn signals...exterior turn signal works but not the ones on the cluster. I have checked fuses, examined wires and even traced them to their sources, all good, even bought a used instrument cluster that had the very same lights out when I installed it in my Jeep. Fuses are good, wiring good.... Is it possible the ECM is bad? Cannot get it inspected without the brake lamp in Texas...tried and they failed me.
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The ecm controls the instrument cluster and it is a common failure. Have you had any codes?

We can know for certain if you send the pcm into us for testing. We run it in our jeep and apply testing costs towards repair or replacement cost if it is the ecm.


Which specific grounds have you checked, verified and cleaned?

I can think of a couple...under the drivers side dash on the kick panel...just under and behind the connector block.

You've also got grounds behind the headlights.

And the ground on the firewall between the battery and valve cover.

Completely agree with testing the PCM...just trying to help!

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While tracing the wiring; did you inspect the wiring harness from the PCM to the sensors and instrument cluster ?
There is a known problem where the wiring harness rubs against the threaded head stud (right rear corner) causing the split wire loom and wiring insulation to wear thru exposing the copper wiring to break or short to ground.
Please inspect the split wire loom that runs along the firewall near the right rear corner of the engine to verify there are not broken or exposed copper wires.