bobejones

I will have to eat shi* on the BCM deal. I determined the dash switch had issues and was not pulling logic power down to ground good enough. I reworked the switch and the fog issue is considered 'fixed', or at least the dash switch was the confirmed issue. Have had a LOT of switch problems in this truck. I have had to tear down every door switch in the truck. Anyway, this now leaves the HVAC. I have never seen a knock off TechII, but would you have a link? I would certainly be very open to just owning one. I do have contacts to borrow a real techII, but always a hassle. Obviously most OBD goodies don't work outside of emissions related stuff.

truck, 2008 3500hd LMM, LTZ, bought used 2 Separate issue. throwing them in the same thread since I rarely get much help on this stuff. Didn't want to waste the air space. 1. Confirmed that BCM will not turn on fog lights on. Switch confirmed to work, and BCM is required to switch a relay under hood. It will not send output to relay. Wondering if there is a way to reference the numbers on BCM to find a salvage piece? I won't pay to reprogram because I don't know if that is really an issue. I am in electronics but without the schematic, the PCB loses me fast so I can't trace the circuit otherwise to verify anything. I do know for a fact the dash switch sends power requesting lights to turn on. 2. For years I have fought with the vent selector actuator switching to default defrost. If in AC dash vent mode, truck VERY consistently starts up with the correct vents, then switches to defrost within 1-10min of running. If I stop the truck and restart it (drop power to climate unit), it will go back to the correct vent setting and will never change the rest of the trip. In many cases, I just leave the truck running to avoid the hassle. For this reason, I am sort of leaning towards the climate dash unit rather than actuator. As an aside, climate unit many times will switch to 'fresh air' mode instead of 'recirc' even though cabin temp is no where near controlled. I will say that even in heating mode, the vent selection issues continue. I have not found anyone with similar symptoms to relate this issue.

Deleted until I can gather more details on my factory GM 350ss truck that did exist.

Sounds like a low voltage issue to me. You need to start looking close at everything electrical. Start at battery and charge system and work forward from there. Sounds more like the main power wire from the battery to the fuse buss. Check the voltage in the fuse box main to see how much loss you have. You may also have a ground issue. When you have something alerting to "low voltage" that coupled with firing issues is VERY related! No, your ABS system should not cause a miss.