2004 XC90 Electrical Gremlins - Ignition Switch?

[ChipStewart]

I hate electrical problems.

My 2004 XC90 was working fine when I turned off the ignition switch. When I turned it back on, the instrument cluster was dark, all the instruments were at zero (speedo, tach, temp, gas, etc.), turn signals weren't working, backup lights were out, power locks wouldn't lock or unlock, the audio system was out, mirror controls didn't work. The engine ran, windshield wipers worked (though not the fluid pump), and I had brake lights. Later, my wife drove home and all worked (at least it worked for her).

Today, I it's not working again. I noticed a few of the times the LED messages would light for a few seconds then turn off. A few of the times, the instrument cluster would light, then fade out (but still no instruments). I tried jiggling the keys, but it didn't seem to make a difference.

Any ideas? I'm thinking it's the ignition switch. Tomorrow, I'll take the case off the steering column and check voltage at the terminals.
I found this diagram:

Ignition Wiring.png (37.28 KiB) Viewed 748 times

but I'm not sure how to read it. I think I should see:
∙ Key out - I should see 12v on Red-Black
∙ I (accessories) - I should see 12v on Yellow
∙ II (run) - I should see 12v on Red-Black, Blue-Red, Violet, Blue, Yellow
∙ III (start) - I should see 12v on Red-Black, Blue-Red, Yellow, Yellow-White

Is this correct? Or am I barking up the wrong tree? Any hints, tips, suggestions, or advice?
Thanks,
Chip

[June]

Sounds like the symptoms my 2004 S80 T6 had when the CEM was on it's way out due to water intrusion. A common problem on these P2 cars. June

[BlackBart]

I went through something very similar recently with my ‘04 XC70. I don’t know if they’re the same. But it was the DIM (“drivers information module” - or the gauge cluster assembly). The lead-free solder mandated then became brittle and many connections on the circuit board fail through heat or vibration. Many of those systems you mention are wired through that DIM.

But verify first if this is an issue with the XC90.

[ChipStewart]

Oh great - just the answers I was hoping I wouldn't get. So, how do I determine if the problem is the DIM and/or the CEM?

[ggleavitt]

Maybe start here- https://xemodex.com/us/dim-cem-low-spee ... flowchart/