H3T Problem with Metra Harness for new stereo

[SedonaBound]

I used a Metra GMOS-04 harness as specified for OnStar systems to install a new Pioneer head unit. This harness gets direct battery 12V power (i.e. not accessory power) and has a processor that controls the head power, warning chimes, etc. per data from the BCM. The new head unit works great, but the Metra harness is not turning it on/off dependably with the ignition and I'm hoping someone has dealt with this.

About 30% of the time, I have to turn the ignition on/off twice for the head unit to turn on. About half the time, it doesn't turn off until a full minute after the key is pulled and door is opened. It seems to be looking for an on/off pulse sequence that's out of synch. Metra tech support told me to pull the new head, re-install the OEM radio, and go through the full on-off sequence to reset the BCM's radio status, and put the new head back in. I did that, and it didn't correct the problem. Did it again and also disconnected the battery. No joy. I also asked Metra if I could just bypass or parallel the power lead from the Metra box to the head by directly tapping a switched circuit; the tech said no. The tech spt seem to read from a list and can't really discuss alternatives. The seat belt, door, and key chimes aren't working right either. I bought the harness with the unit at a Best Buy 70 miles away, so returning it is a big deal. Any ideas?

I've had other issues with the Metra harness too. Next time, I'll pay for the installation; this has been a royal PITA because of the harness.

 

[sjwoodwalker]

I had bought the same one but mine has worked fine so far. I know i read that alot of people had all different kinds of problems with these. Usally they said that they exchanged it for a new one and it worked fine. Hope this helps some what.

 

[napalmsticks]

Mine works fine also.

 

[derian06]

Wire the harness to the ignition fuse not the battery.

 

[Graham2990]

I'd try what others suggested. Wire the harness power directly to a 12v RAP circuit. Not sure why the Metra tech said not to do that. Colorado's actually require that you run your own 12v RAP directly to the radio, bypassing the harness entirely like you'd described.

If that doesn't help I'd say you've gotten a bad unit somehow and an exchange is in order.

 

[SedonaBound]

The head unit needs both battery 12V (for the clock and memory) and RAP for normal operation, and I still need to provide battery to the harness module for the chimes and OnStar. I'll probably do it Saturday and see what happens; I think I can take the head unit out blindfolded now.

 

[SedonaBound]

Mea culpa. Not a Metra issue. I pulled the head again and looked real closely at everything. I discovered that I wasn't connecting the Metra plug directly to the factory harness plug, but to a harness extension with a branch leading to something not visible. Maybe to the sat radio receiver or OnStar? The plugs and wrap looked exactly like the factory wiring. I looked on the wiring diagrams that ID every plug in the harnesses and it shows no extension or extra plugs there for any version or audio option. I went back out and tugged on the branch wires, and up came an little iPod adapter box jammed way down under the ducting. I removed this harness extension and plugged the Metra harness directly into the actual factory plug and, voila, the RAP power and warning chimes are all working as they should. Oops. It would be nice if installers would label non-stock stuff that looks like it's factory.