Quick history: 2005 LS Sport Coupe. Massive front end damage back in October 2006. A few weeks ago, corrosion killed some cheap butt connectors on the front wiring harness. I replaced all the connectors with soldered connections, unwrapped and inspected the entire front harness, rewrapped it and rerouted the front harness from in between the washer bottle and the frame to inside the gap between the radiator and the header support. I relocated the front harness ground directly to the chassis ground on the battery box.
Everything was fine up to yesterday.
I put the car in drive and the DRL indicator on the dash and the relay started clicking then stopped and the service indicator came on. DRL's inoperative. Low beams inoperative. High beams work. Fog lights work. All turn, marker and taillights work. All fuses intact. Three BCM codes came up.
B2600 Daytime running lamp error
B2965 Key in Ignition Fault
B2662 Park lamp switch circuit fault
Starting with the first, I used the scan tool to turn on the DRL's. The relay clicks but no lights. Checked the relay connections and probed the positive circuit of the relay coil and relay output. Checked the relay control circuit into the BCM for ground. All as it should be.
Checked the headlight connectors themselves. Battery voltage at the B wires. Ground the C wires (pink) and the high beams come on. Ground the A wires (blue) and the low beams come on. So the bulbs are good.
Move to the mulifunction switch. Disconnect the blue connector C1 and jump wires B (high beam signal) and ground E and high beams come on. Jump wires C (low beam signal) and ground E and nothing. HOWEVER, I'm getting battery voltage from wire C at the connector. There's continuity between wire C at the connector, post B6 at the BCM connector, and wire A at the headlights.
Could a bad BCM throw me off this much? I don't understand why I could be getting battery voltage from the low beam signal to ground with my voltmeter but when I ground the wire nothing happens. The ground must be good because when I ground the high beam signal the high beams come on. I am absolutely stupified.
