davepl

I asked in the general C7 section, no one knew. Maybe someone here has a little more background!

I had my third brake light out, and OnStar emailed me about a malfunction with it.

I connected HPTuners and pulled the DTCs, but there were none. I reset them anyway, logged into OnStar, and see there are no warnings, everything is green and good to go.

Is it possible that HPTuners can reset DTCs that it can't read? And/or are things like burned out/defective lamps kept wholly separate from ECM DTCs?

I don't know that much about it, but I've got a hunch that pulling DTCs only pulls them from the engine or trans module you're connected to, but perhaps clearing DTCs does a broadcast that erased the brake light warning from whatever module it was in, even though it wasn't reported when I pulled them.

Anyone know? I don't know Jack about OnStar diagnostics.

Thanks,
Dave

davepl

This site is all geeks and no nerds? Come on, someone must be into the gory technical details. I can't be the only one with a laptop and a scan tool!

Bill Dearborn

HTC Tuners doesn't have any access to body codes so is pretty much useless seeing ~ 45% of the codes that can occur on the car.

Bill

davepl

I know, but I think my question is "does a DTC reset clear codes in ALL modules, not just the ones that HPTuners is aware of"?

So it can't read from the Body Module as an example, but it appeared to be able to clear the trouble.

My guess, then, and what I was hoping to learn/confirm, is that a DTC reset is a "Broadcast" to all modules listening on the CAN bus rather than a module-by-module or DTC-by-DTC reset?