I have intermittent H74 LED Dimming Circuit Open or Shorted.

I ALSO have a CONSTANT - --- --- pic below, on A/C Control Head (should be --- --- ---), for E & C Bus Failure.

Neither diagnostic flow chart defers to anything related to the other (that I see yet).

Does this pic look like it could be 3 identical dashes?

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THAT'S HOW THE AC CONTROL HEAD ON MY '96 LOOKED WHEN IT DIED.

I wish. But I have issues with radio head unit too...

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Schrade, I've had the same code for 10 years.
I haven't looked in the FSM lately (cause I don't care anymore)but IIRC it's the circuit that dims the dash when it gets dark out.
There's a sensor on top of the dash that reads ambient light for that circuit.

I've never seen this cause a problem, dash dims like it's supposed to. So, I ignore it. Clear it when I check codes but it always comes back.

Good luck with the A/C stuff.

If the AC head has died, Dr Dons can fix... my bigger concern is the AC Programmer...

Besides the A/C LED Code - pic above, my blower is running constantly.

And radio is inoperative, along with A/C head Unit.

Haven't pulled the dash yet, which is necessary in all 3 diagnostic flow charts.

I've read all 3 flow charts to the end, looking for convergence to common source. It SEEMS to be CCM, but I have to know for sure.

Back-probing circuits is the hardest job I think, above motor pull, tranny pull...................

Non defer to other symptoms, for FIRST diagnostic, which occurs often with multiple DTC's.....

No common ground faults?

The CCM might fail, but I would be surprised if it caused those items to fail. The CCM monitors, for the most part, not controls.

CCM ground was part of Top End Resto:

CCM grounds (Yellow circle) got same treatment as ground in hand - cleaned, dielectric grease, re-seating.

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