Hey guys, I know there are some threads with similar issues but I just haven't found a solutions to my problem. I installed after market stereo and the running tail lights, shifter lights in the center console, and cluster dimmer stopped working everything else works fine. I replaced the multiplex unit brand new from honda and still no running rear lights etc... please help. I've checked and double checked all fuses. I also read some where that a faulty turn signal switch solved this issue for another guy, would a bad turn signal switch assembly be related to the rear running lights ? please help.

 

1. In regards to the aftermarket radio installation, most aftermarket wire harness kits have a dash dimmer wire (generally it is an orange colored wire on aftermarket wire harness kits). If that orange wire from the aftermarket radio is hooked up to the car’s gauge cluster's dimmer wires, it can and will blow out the multiplex control unit (mcu). – Leave the aftermarket dash dimmer wire unconnected to make it simple.

The car’s dash light brightness control (dimmer – located in the gauge cluster) has two wires (a Wht/Red wire and a Red/Wht wire) which are bus communication wires leading to the driver’s mcu. Connecting a wire to these dimmer bus communication wires can blow out the mcu. In addition, hooking up any wire incorrectly to the red wires (which are the ground source wiring coming via the mcu) at any interior illumination that can be dimmed, can also blow out the mcu.

2. If the wiring was not corrected for the aftermarket radio installation, you can blow out a new MCU.

You can check whether it is still related to the MCU by following this video:


3. If it is not the MCU, then I can guide you do some troubleshooting to narrow down the problem area. You will need a voltmeter/multimeter.

 

Thank you for the response, I will be picking up a voltmeter/multimeter tonight after work, since I corrected the wiring issue before installing the new mcu.

 

The following will be tests to try to narrow down the area of the problem. Do not replace anything yet, report your results and I will give you further guidance, to step through what may be the issue.

On your EX, you have a tail light relay located on the passenger side. See attached images for location.

Power for a lot of various lighting issues you mentioned has to run through this relay. If you have a voltmeter, you can test a few wires there to diagnose to narrow down the area of issue(s). You will want to backprobe a few wires. Backprobing is either using a backprobe set or using a thin needle or something and making contact with the metal terminal of the connector without piercing the wire in the back of the still connected connector. Care must be taken to ensure that the wiring does not get damaged. You can use something like a T pin, available at Walmart, etc., and backprobe. These pictures are just to give a picture of the concept of backprobing without piercing any wires.

https://www.hondaaccordforum.com/foru...%5D-t-pins-jpg

https://www.hondaaccordforum.com/foru...back-probe-jpg

1. At the tail light relay (with it still plugged in), with the voltmeter’s black lead touching chassis/body metal ground, use the voltmeter’s red lead to backprobe the Red/Blk wire at the tail light relay. There should be voltage at the Red/Blk wire with the combination light switch turned on (i.e., parking lights or headlights on). (Red/Blk wire should be a wire with red color insulation and a blk stripe.)
2. If no voltage in above procedure;, with the voltmeter’s black lead touching chassis/body metal ground, use the voltmeter’s red lead to backprobe the Red/Grn wires at the taillight relay with the combination light switch on. There will actually be two separate Red/Grn wires there, one Red/Grn wire (terminal connector 2 pin) is coming from Fuse No. 10 in the passenger side fuse box, the other Red/Grn wire (terminal connector 5 pin) will be coming from the driver’s multiplex control unit. There should be voltage.

Post your results to help give info. on whether the issue may be before or after the relay.

 

You said you check all fuses but I really think you simply blew a fuse. You can't always visibly see a fuse is blown. It's best with a multimeter checking the outside for continuity as it will beep.

 

OK guys, Thank you for all the responses and apologies for the late response.SO, it was a freaking fuse had to check them with mulit meter, everything is back to normal. Thanks again for the help, couldn't have done it with out your help.