Puzzling Fog Light Error Code

[jcerrona]

I've got a 2010 RS, SE5.
The check-engine light almost always comes on when I first turn the key when the engine is cold.
I brought it to a dealer who pulled the code: P1678 "Fog Light Relay Circuit Shorted to Ground or Open Circuit".
The annoying thing is that there are no fog lights on this vehicle. :sour:
I've taken the whole front end apart, cleaned every lighting harness connection, and checked every fuse in the hopes that it was something simple. No success.
The only way the check engine light goes away is if I start the engine, turn the key off, and then turn the key back on (and then start the engine).

Not a big problem right now, just really annoying, but potentially a big problem if I just learn to ignore the check engine light and I don't take heed when something serious goes wrong.

The only electrical modification this spyder has was that the previous owner wired in a 12 VDC adapter for his GPS.

Anybody have any ideas?

Thanks!
Jon

 

[DrewNJ]

Where is the GPS adapter wired in to? Its not wired into the nonexistent foglights is it?

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[jcerrona]

The cable going to the 12 VDC is bundled together with the horn cable. I can't tell where it goes from there.
As far as I can tell it was a professional job done by a dealer. I doubt it is related to the fog light error code problem, but you never know...

 

[Chupaca]

Don't know..!!

has it always done this..?? Have you checked the fueses..?? You may have to seach the wiring to see if any have been damaged. Something is affecting the fog light circuit. Check engine light should come on when key is switched on as well as all the indicator lights. Once the engine is started they should all go out if all is well. Let us know what you find...:dontknow:

 

[NancysToy]

P1678 - ECM - Fog Light Relay circuit shorted to ground or open circuit

Cause - Blown fuse, damaged or disconnected accesory relay, damged circuit wires, damaged connectors, or damaged ECM output pins.

Service action-
Check fuse F12
Disconnect 2-HLC connector
Measure voltage between harness connector 2-HLC-1 and ground (expected value 11 to 13 volts)
Measure resistance from harness connector 5-ECM-B16 to 2-HLC-6 (expected value <2 ohms)
Measure resistance between headlamp harness connector 2-HLC-1 and 2-HLC-2 (expected value 120 ohms)

 

[jcerrona]

Thanks for your help

Thanks everyone for your input, especially for the error code cause and service action.
I will definitely try these things and let you know if I'm able to solve it.
There is no fog light fuse because there are no fog lights, but I have checked all the other fuses for the heck of it. I couldn't find any blown fuses.

 

[billybovine]

Thanks everyone for your input, especially for the error code cause and service action.
I will definitely try these things and let you know if I'm able to solve it.
There is no fog light fuse because there are no fog lights, but I have checked all the other fuses for the heck of it. I couldn't find any blown fuses.

When you do find an answer please let us know.

 

[jcerrona]

Solved

DrewNJ, you were right about it being wired into the fog-light circuit.
Chupaca, I did check all the normal fuses, just not the one that mattered :shocked:

Apparently whoever installed the 12 volt adapter used the un-used fog light power circuit to do so. It turns out the cheap 12 volt usb power adapter (used to power a GPS) had a broken fuse and missing parts. I replaced the 12 volt usb power adapter and the problem went away. The power circuit needs to be closed for the ECU to think the fog light circuit is OK.


I'm not a happy that the previous owner/dealer thought it was a good idea to use the fog light circuit to power the 12 volt adapter, but glad it's solved...maybe someday I'll re-wire it.
I doubt the solution to this problem will help many other people, but thank you all for your comments.

 

[DrewNJ]

Its an easy unused circuit to tap into. I have a friend that used the same circuit to wire up his alarm. That's what gave me the idea.

Glad you got it straightened out!

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