2002 Honda Civic, A/C and Door Locks Do Not Work

This 2002 Honda Civic came in with several complaints among which were the a/c compressor would not turn on, the power door locks did not work, the wipers did not work, the interior lights did not work, the warning chimes did not work and the brake warning light on the dash stayed on. The only commonality I could find between all symptoms was the multiplex unit that is part of the interior fuse box.

The next part of my testing was to perform the self diagnostic check of the system. To do this, I first had to locate the diagnostic connector. It is located to the right of the yellow connector, that is slightly left of center in the picture below.

The manual states to use a “special tool” into the diagnostic connector. The special tool is a jumper wire. I hooked up one of my fused jumper wires as shown below. The test actually begins with turn the ignition switch on (position II). With the driver’s seat belt unbuckled the seat belt reminder chime will beep 6 times. Next, set the ceiling light switch to the center position and close all doors. Now, we are supposed to install the “Special Tool”. I had previously installed my jumper with the fuse/circuit breaker removed and simply installed the fuse/circuit breaker at the appropriate time. I had surmised that this would be much easier to do than trying to install the connector, while sitting in the driver’s seat with the door closed.

After about 5 seconds the ceiling and spot lights were suppose to go into diagnostics and flash codes. This system would not go into diagnostics. After not being able to go into diagnostics, you are supposed to check for power and ground circuits, as outlined later in this post.

Testing begins at the underhood fuse box.

My Mitchell information system stated that fuse number 9 in the under hood fuse box needs to be tested. It is also listed on the cover as “Backup”.

I checked the fuse and it was good and had power on it.

Going to the interior fuse box the instructions state to check fuse #10 (7.5 amp). It was good, so I dropped the fuse box down to do more testing. I checked for ground at the black wire (position #4) in connector “J” as shown below. It was good.

Next in the same connector, I checked for battery power at white/red wire, terminal “J2”. It was present. By the way that wire is supplied power from fuse #9 in the underhood fuse box. I have now confirmed that the the wire is good between the fuse #9 and this terminal.

Since the power and ground signals were all present and the multiplex unit would not go into self diagnostics, my conclusion was that the multiplex/fuse block unit was faulty. I installed a new unit (purchased from my local Honda dealership) and all systems were back working properly.