Gauge assembly and AC controls backlight not working

Maintenance/Repairs
1

I am having a problem with my 2002 Civic LX. My gauge assembly only works intermittently. For the most part it does not work at all. Speedometer, tachometer, fuel gauge, etc. all do not work. Also, both the backlight of the gauge assy and the one for the AC controls do not work.

I have checked fuses, pulled apart the gauge assy to check connectors, checked the cruise control switch (operated by the clutch) and all seem to be in good shape. Has anyone else had this problem or know of anything else I can check? I’m thinking it could be a bad ground somewhere but I’m not really sure where to check.

2

You’ll probably need a schematic to figure this out. The gauges are probably intimately connected with the computer. So it could be a computer problem. But the gauge module at the minimum needs to be supplied battery voltage and ground, so you might could check for that at the connectors. But you’ll need a schematic to see what the wire colors are. Usually battery voltage is red or has a red stripe at least on the wires. And they’ll be a fuse in that wire somewhere, usually either in the engine compartment, or under the dash, kickpanel fuse/relay box, etc. And ground is usually black. But don’t guess, find a schematic for the gauge cluster first. Once you have that, post it here and maybe the folks here can decipher it.

3

The trouble is most likely due to a lack of power rather than a bad ground connection. Verify the fuses in the panel under the hood are getting power through them using a test light probe and placing the probe on the slits on each side of the fuse. There should be a yellow wire going to the cluster that should have 12 volts on it from fuse 10 in the panel under the hood.

4

Thanks for the comments. I’ll try a wf things and let you know.

5

All the lights you’re having problems with could be caused by a faulty multiplex control unit located in the fuse box under the dash.

Enter “Honda Multiplex Control Unit” in any search engine and find out about it.

Tester

6

I’m having trouble finding a gauge assembly schematic but I ran the diagnostic on the MCU that is described in the service manual. I am getting an error code saying that the MCU cannot receive signals from the ECM (DTC 2). Do you think this is the source of my problem? I have gotten to the ECM but I don’t have schematic for that either.

I’m not exactly sure how to proceed. I don’t really want to buy a new one unless I know it’s faulty and what caused it to fault. I installed an aftermarket stereo and I’ve heard that they can cause problems in the controllers. Do you think this has something to do with it?