Hello, I have a 08 gtc and my high beam headlights do not work, they will activate with the handle to “pass” but, they will not stay on. Any suggestions on what may be wrong. Thanks Pat

 

A cursory glance at IETIS suggests that the headlamps are switched by the Front Body Control Module (BCM). There appears to be no difference in the path between the BCM and the bulbs depending on which headlight function is required (flash or 'permanent').

That BCM receives discrete control signals from the “Light Switch Illumination” panel; seemingly grounding the appropriate pin to command each lighting function.

Your fault is therefore likely to be:

• A faulty BCM, probably because of water ingress.
• A faulty light switch.
• Faulty discrete cabling twixt switch and BCM.

A poor ground at that lighting panel would cause a problem, and you can check for this by whether the panel dimming switches operate correctly, because they share that ground path.

It is of course possible that if the panel lights aren’t working anyway, then it will be impossible to deduce whether the dimming function is ok. (The same applies to the fog lights).

Rather than using discretes, the BCM receives CAN Bus signals from the Steering Column Stalk, and that you say is working correctly.

To check the wiring, if you can get to the back of the switch panel with a DVM then Pin 1 Yellow should have 12V on it.

Grounding this pin through a diode (because there is one in the switch panel) should cause the BCM to illuminate the headlamps. This will prove a test of the switch panel.

That yellow wire should connect to Pin 17 of the BCM connector, so you can repeat the 'ground through a diode' test here.

If this last test doesn't cause the lights to illuminate then it’s your BCM I’m afraid.

HTH

 

HTH, Thanks for the quick response. I will do the checks this week and let you know how it turns out. Thanks Again.

 

​​​​​​Hello @pdunigan ,
So I follow correctly, when you pull the stalk towards yourself the highbeams illuminate for flash to pass, but when you push the stalk forward you get nothing, when you push the stalk forward does the blue highbeam indicator illuminate in the cluster as it does with FTP ?

Johnny

 

Johnny, no illumination or high beams when pushed forward to engage them, they work when pulled to pass. Thanks Pat

 

Question, what is the process for replacing the BCM? Battery disconnect, and programming needed? Thanks Pat