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Dan, ASE Certified Technician
Category: GM
Satisfied Customers: 2270
Experience:  20+ years in automotive repair work
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2007 Pontiac Grand Prix: low beam..(intermittently)..10 minutes

Resolved Question:

What causes the low beam headlamps to go out (intermittently) on my 2007 Pontiac Grand Prix? I still have the inside high beam lamps, but have to turn the multifunction switch to headlamp from the auto function. This usually happens a short time after starting the car (5 to 10 minutes or less). At times they will come back on for a short period of time. This is very inconvenient when driving at night as I have to keep the high beams burning in order to be able to see and not being certain the low beam lamps are on or not. I have replaced the multifunction switch and this problem subsided for a short time (3 to 4 weeks). I have recently had the vehicle to a GM (chev) dealership but they could not (or would not) find a problem. Could this be a problem with the low-beam headlamps relay #35 for the 3800 V6 engine?
Submitted: 6 years ago.
Category: GM
Expert:  Dan replied 6 years ago.
Hello JACUSTOMER-kxd0t8dg-

The Multifunction switch will not make the low beams go out. It can affect the high beams but not the low beams. The BCM ( Body Control Module ) controls the Lighting functions. When the BCM sees that its dark enough for the headlights to be on from the readings from the light sensor, It turn the low beams on unless the high beams are selected on the switch, Then it will turn the low beams off and the high beams on, With this problem your having, You have either a Bad BCM, Light sensor or a HDM Module( low beam relay). This is hard to diagnose due to the fact that it doesn't act up long enough to do some tests. What I do on these cars with this problem is to check for codes in the BCM and if no codes, I replace the HDM module. I have never had one come back after I replaced the HDM module for this problem. I have seen probably around 10 of these cars with this problem. The HDM Module is like a relay but it has a Logic board in it that can go out when it gets hot.
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