Any suggestions on this issue? It just started happening yesterday A.M. The parking lights come on for a bit then turn off then back on. Have to disconnect battery to keep them from running when car is parked for the night. I can't control them with the headlight switch unless ignition is in ON position.

The BCM reads the lamp switches (only) from the combination switch when the vehicle is off, so most likely you have a problem with the combination switch contacts. However, it's also possible the problem is in the IPDM, which actually drives the tail/park relay. You need to catch it in the act with a streaming scanner that can read the combination switch from the BCM. If the BCM shows the switch going on and off then it's most likely a bad switch, if there's no action on the switch then it's most likely a bad IPDM.

PS - Both the BCM and IPDM should be "alive" on CAN with the ignition off, so you should be able to scan both in a key-off doors-closed condition by dropping the driver's window with the scanner connected before closing up the car.

Thanks for your input! I was talking to auto tech yesterday and he said something similar to this. However forgot to add that I hear clicking sound from the fuse box behind battery(ipdm) when the lights turn on and off.

You're most welcome. That will be the taillamp relay you're hearing, but since the IPDM runs the lights under CAN instruction from the BCM, you need to know whether the BCM is telling the IPDM to turn the relay on. If there's no instruction then the IPDM is defective, but if there is, either the switch or BCM is the culprit.

What switch is being mentioned? my headlight control switch by steering wheel?

so it is possible the headlight switch is now defective and is turning them on and off when the car is off?

Yes, the headlight stalk, if it has a failing diode or a resistance path (usually carbon) in between switch throws.

I know you can self test the Ipdm (self diagnose) but is there a way to test the BCM diy. I'm hoping it is just the headlight switch.

JJM158 wrote: ↑

Wed Apr 21, 2021 2:52 pm

I know you can self test the Ipdm (self diagnose) but is there a way to test the BCM diy. I'm hoping it is just the headlight switch.

Not that I know about. The BCM is a much more complicated beast than the IPDM. For most purposes the IP is nothing but a smart relay driver, while the BCM is the brainiac for practically everything but the engine and trans. You could try simply pulling the steering wheel trim and unplugging the Combination Switch to see if the lights stay off. The BCM may throw some codes, but it should tell you if the switch is responsible. If not, I can help you locate the combo switch connector at the BCM, unplugging it there should indicate whether it's an issue with the switch-matrix wiring. If both of those prove good, then it's either a bad IP or a bad BCM. At that point you'll definitely need a scanner to determine which.

My car was doing good for past 2 days and since went through car wash today it started again. My ipdm has clicking relays and is making a humming sound, and noticed that there's a bit of water by fuses...

The IP's are water-resistant but not proof, hope you didn't drown it. Rice may work if you did, but find out how the water is getting in there.

Yeah it was strange that it happened again after a few days of no issues, when I got home after car wash the lights, relay etc started acting up

Reminds me of this thread - crazy-electrical-problem-t566725.html#p6668904

EdBwoy wrote: ↑

Sun Apr 25, 2021 8:46 pm

Reminds me of this thread - crazy-electrical-problem-t566725.html#p6668904

Wow, good info! Must be an "M" thing, I've never seen an IPDM enclosure holding water. Relay boxes yes, if the cover is off, but not an IP.