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Hummer H3For the Hummer driver who wants the rugged look and off road capabilities of the Hummer, but in a smaller size and with a more fuel economy friendly engine.
Did some testing on my switch tonight, using the wiring diagram from Page 19 of the electrical manual linked on Schwarttzy's site. For reference pin 3 (purple) is ground, pin 1 (blue w/ white stripe) is the positive from the master cut off switch and pin 11 (also purple) is the positive from the dome light trigger on the dimmer slide wheel. results are as follows:
- When dimmer slider is up to the top (in the position that would turn on the interior lights) I get continuity between pins 3 and 11. If I turn the slider down I get no continuity on these pins
- When the master off switch is pushed in I get continuity between pins 1 and 3. When it's in the out position I get no continuity.
- Both of the above happen independent of each other.
- I'm also getting continuity between pin 3 and some of the other pins but didn't search through the manual to see which was which. I'm guessing that pin 3 is a common ground to more than just the interior lighting.
Based on how I think the switch should work all the above checks out to the switch still being good, do you all agree?
I also tried pulling the fuse that the remote starter is wired into (e-brake) and there was no change. When I pull the fuse for the BCM the lights go out, but I'd expect that since the wiring runs from the switch, through the BCM and into the lights themselves.
I've booked an appointment for Tuesday to take it into the shop but I really hate giving up (and paying shop rates). If this is just a short somewhere would the circuit fail in a completed state to keep the lights on? If the fuse for the remote starter doesn't affect the lighting I'm really worried it's something in the BCM.
Any ideas from anybody before I give up and go to the shop? I'm concerned they'll burn a lot of hours chasing the problem and default to a bad BCM, which will come with an expensive price tag...
I would try disconnecting the switch that controls the interior lights and then operating the vehicle like normal. The headlamps should not work either so do this during the day. If the interior lights stay on it is not the switch. The prints I have for the 2007 show 2 purple wires and a blue/white. One purple is a ground reference supplied by the BCM and the other 2 are input signals to the BCM. By removing the switch you eliminate those inputs to tell the BCM to turn on the interior lights. That is, unless one of those wires is grounded. Let us know the final verdict; I've had to chase a few electrical gremlins myself and they are never fun.
Heard back from the shop, they say it's a white wire (not sure on the pin number) coming out of the BCM that is supposed to cut ground signal but is staying live (if live is the correct term for a ground). Hard to say if that is also the only thing causing the battery drain issue because it's a new symptom, He wasn't convinced that removing the remote starter would fix the drain issues and thinks that the BCM is the main culprit. Waiting for a call back from the dealer for BCM replacement and programming. Having trouble justifying the ~$800 that they would charge me to replace the BCM just to turn off some lights that I could just unplug.
As for the switch diagnostic I tried running things without the switch present and everything still worked normally, headlights, dash illumination, interior lights. I did notice some flickering in the dash lights though - maybe there's a capacitor somewhere that wasn't wired in?
Lastly my side mirror control has never worked on the truck as long as I've owned it. On the one wiring diagram I looked at it showed a tie-in to that and the lighting inside the BCM. That shouldn't be the issue, right?
Plug in a good scan tool, look under Inputs in the BCM section. You can see all of the switch input status including doors and dash switch. Close all of the doors, wait for at least one minute for the timer to time out. All switch inputs should read Off. If one of them reads On, remove that switch and try again.
Plug in a good scan tool, look under Inputs in the BCM section. You can see all of the switch input status including doors and dash switch. Close all of the doors, wait for at least one minute for the timer to time out. All switch inputs should read Off. If one of them reads On, remove that switch and try again.
While I don't have a scanner that could read the BCM the mechanic told me two codes came up, one for door switch low voltage (replaced the switch about 6 months ago and has been working since) and one for the white ground wire off the BCM. The switch is sending the correct signals to the BCM but the BCM isn't switching off the ground like it's supposed to.
This does make me want a new scanner though, does anybody have experience with the Blue Driver bluetooth pro module? (
) It has good reviews so I'm tempted and alludes to the fact that it will read the BCM but confirmation that it works for the H3 would be fantastic if anybody else has used it.
I'm asking Hummerz if the LAUNCH X431 CRP123 Diagnostic Tool OBD2 Auto Scanner can read data from the BCM? Kind of like the guy in his garage scanner, doesn't cost an arm and a leg.
I know they can do a bunch of stuff, used one to diagnose an SRS problem couple years back with a friends H3.
I'm asking Hummerz if the LAUNCH X431 CRP123 Diagnostic Tool OBD2 Auto Scanner can read data from the BCM? Kind of like the guy in his garage scanner, doesn't cost an arm and a leg.
I know they can do a bunch of stuff, used one to diagnose an SRS problem couple years back with a friends H3.
I don't think so Doc. If your looking for a reasonably priced multi systems scanner:
I heard back from Tech support at BlueDriver and they said it will read BCM codes. Only one way to know for sure I guess, and I can always return it if it's a no-go.
For anybody curious, I received my BlueDriver unit and confirmed that it does in fact read BCM codes on the Hummer H3 (at least the 2016 one that I have). The only one that came up was the low voltage warning to my driver's door window/lock switch which I replaced previously. The other fault that the mechanic talked about didn't show up, though he probably cleared it last time he did the reading. I tried plugging in the dome light again but it's still on constantly. For the time being I'm driving with all interior bulbs unplugged to mitigate unnecessary draining. Trying to decide if I want to pay for a new BCM or not.
07-31-2019, 11:26 PM
