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Dash and tail lights not working?

Tiny
CARLOSV3326
  • MEMBER
  • 1998 HONDA ACCORD
  • 2.3L
  • 4 CYL
  • 2WD
  • MANUAL
  • 200,000 MILES
My dash and tail lights do not want to come on. I replaced both mcu's, checked the dimmer switch and replaced the combination light switch/headlight switch.
Tuesday, October 2nd, 2018 AT 7:11 AM

27 Replies

Tiny
KEN L
  • MASTER CERTIFIED MECHANIC
  • 43,290 POSTS
Hello,

It sounds like you have a tail light relay that is out. Here is a guide to help you test it and the relay location with the wiring diagrams so you can see how the system works:

https://www.2carpros.com/articles/how-to-check-an-electrical-relay-and-wiring-control-circuit

Check out the diagrams (below). Please let us know what you find. We are interested to see what it is.

Cheers, Ken
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Monday, May 17th, 2021 AT 12:29 PM
Tiny
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  • 17 POSTS
I checked the taillight relay and it is good. I checked all grounds and they look good.
My clock is working fine so the circuit must be good. I checked and tested the light fuses under the hood fuse box and everything checks out.
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Monday, May 17th, 2021 AT 12:29 PM
Tiny
CARLOSV3326
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  • 17 POSTS
When I connected my test light to this wire red with green stripe all the dash, taillights and climate control lights came on but it was like they stayed direct meaning it was as if they were getting direct power because they stayed on even with the key off the ignition and light switch off. If I had the wiring diagram for this plug maybe I could get somewhere.
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Monday, May 17th, 2021 AT 12:29 PM
Tiny
KEN L
  • MASTER CERTIFIED MECHANIC
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Hmm, yep I can get you the diagrams does that connector go to the HVAC system?
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Monday, May 17th, 2021 AT 12:29 PM
Tiny
CARLOSV3326
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  • 17 POSTS
No thats the connector to the passengers side multiplex unit. Also the plug to the passengers side fuse box has no power at none of the wires.
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Monday, May 17th, 2021 AT 12:29 PM
Tiny
KEN L
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I see the drivers side multiplex unit involved in the lighting system just two wires which are controls the taillight relay. Lets try jumping the wires to see if the system comes to life. Red/green - red/black let me know.
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Monday, May 17th, 2021 AT 12:29 PM
Tiny
CARLOSV3326
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  • 17 POSTS
On the taillight relay itself or on the drivers multiplex plug?
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Monday, May 17th, 2021 AT 12:29 PM
Tiny
CARLOSV3326
  • MEMBER
  • 17 POSTS
I jumped the red/green with the red/black on the taillight relay plug and the lights did come on, but I turn the light switch on and off and the lights stay on even with the key out of the ignition and light switch on the off position. Then when I un-jump the connection they turn off and do not work anymore. Here are the two wires I jumped on the taillight relay plug!
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Monday, May 17th, 2021 AT 12:29 PM
Tiny
KEN L
  • MASTER CERTIFIED MECHANIC
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Can you make sure the bulb are grounded? Here is a guide to help confirm. Check the wiring diagrams to see where you are losing power.

https://www.2carpros.com/articles/no-tail-lights-exterior-running-lights-tail-lights-out

Please run down this guide and report back.

Cheers
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Monday, May 17th, 2021 AT 12:29 PM
Tiny
CARLOSV3326
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  • 17 POSTS
I have no clue what wires I have to check to see if the bulbs are grounded or not and or what wires are power?
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Monday, May 17th, 2021 AT 12:29 PM
Tiny
KEN L
  • MASTER CERTIFIED MECHANIC
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Sorry, here is a guide that will help you get started. See if there is power coming out of the red and black wire from the tail light relay with the lights on.

https://www.2carpros.com/articles/how-to-check-wiring

Please run down this guide and report back.

Cheers, Ken
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Monday, May 17th, 2021 AT 12:30 PM
Tiny
CARLOSV3326
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I think that red and black wire is a ground and the red and green is power. Correct me if im wrong! I hooked the multimeter to both red and green wires also the red and yellow wire and got 10 volts my batties need charge and I did a continuity test on the red and black wire (red probe on the red and black wire and black probe on ground wire) and it went beep and marked 000.
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Monday, May 17th, 2021 AT 12:30 PM
Tiny
KEN L
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Red and black should have power when the relay is engaged.
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Monday, May 17th, 2021 AT 12:30 PM
Tiny
CARLOSV3326
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No it does not. The red and green has power. I checked the taillight plugs for power as well and nothing.
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Monday, May 17th, 2021 AT 12:30 PM
Tiny
CARLOSV3326
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When I check for voltage at the red and black wire nothing happened. I even hooked up my test light just for a little reassurance and nothing.
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Monday, May 17th, 2021 AT 12:30 PM
Tiny
KEN L
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If the relay is working the red and black should have power check out the wiring diagrams above it shows the connection.
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Monday, May 17th, 2021 AT 12:30 PM
Tiny
CARLOSV3326
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  • 17 POSTS
Red and green is power or am I reading the diagram wrong. I highlighted the wires on the diagram below that are hot at all times. Does that not make it a power wire? Also, I checked the relay and it was good, I even replaced it with a new one to be 1000% sure. If the red and green is power then the relay is getting power to it.
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Monday, May 17th, 2021 AT 12:30 PM
Tiny
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Also, does the 1998-2002 Accord Coupe exterior lighting circuit schematic differ from that of the 1998-2002 Accord Sedan four door or is it the same thing?
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Monday, May 17th, 2021 AT 12:30 PM
Tiny
KEN L
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See the wiring diagrams and the switch of the relay goes to red and black which goes to the lights. Put power down red and black to see if the lights come on.
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Monday, May 17th, 2021 AT 12:30 PM
Tiny
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Yes they did come on.
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Monday, May 17th, 2021 AT 12:30 PM

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