C0327 while in A4WD?

Maverickxeo

Registered Member
Original poster
Jan 25, 2021
40
Alberta, Canada
On my 04 Envoy 4.2L, I've noticed twice a 'minor' error.

The first time, I was driving on the highway and it was pouring rain. I put the Envoy into A4WD just in case and it worked flawlessly - but it tripped a C0327 code. It would NOT shift to 4WD or 2WD (by turning the switch). Once I shut off the engine and turned it back on, it was good and all worked as expected.

The second time, I was driving on a gravel road and I put the Envoy into A4WD. This time, I forgot to take it out of A4WD while on (mostly) dry pavement. The code tripped while on dry pavement, but it worked as expected. I had the same issues of being unable to shift it out of A4WD, and was able to 'fix' it again by turning off the engine and turning it back on.

Is this just a minor 'quirk' while in A4WD? Like I said - when in A4WD, it shifts from 2WD to 4WD properly even while the code is tripped.
 

Mooseman

Master Blaster
Moderator
Dec 4, 2011
21,859
Ottawa, ON
Already lots of info in this thread:

 

Maverickxeo

Registered Member
Original poster
Jan 25, 2021
40
Alberta, Canada
So as an update, I had the same thing happen - but this time, it was more 'serious.' The code tripped (and the dash light) and I lost ALL the lights above the switch. I turned off the engine and shifted it to 2WD, and the four lights (plus N) would show up on the switch when I fired it up, but the lights would all go out and it would NOT shift. It seemed to be stuck partially in 4wd - if that makes sense since it seemed to hop slightly. I disconnected the battery, and moved the switch, checked the fuses, etc. and it made no difference. I slowly returned home, and then turned off the engine, and turned it back on - it was functioning 'normally' again.

I had an assistant shift the TC while I laid underneath and moved the wiring around - no difference in shifting. I then noticed that going from A4WD to 4WD, there was a normal motor 'sound,' however, going back to A4WD, it seemed to 'lug' if that makes sense. It took longer and it sounded like the TC motor was straining REALLY hard. This was NOT present in going from 2WD to 4WD, 4WD to 2WD, or 2WD to A4WD (or back).

I am going to replace the motor since I believe that the motor straining is causing it to 'overheat' and then stop working - am I on the right train of thought?
 

Mooseman

Master Blaster
Moderator
Dec 4, 2011
21,859
Ottawa, ON
All the lights going out usually indicates that the TCCM is bad. This was the problem with the 02's and some 03's. I'd try and replace it with one from a junker. Be sure to get one from an 04+.

Although 04 were not affected by this particular defect of the 02's, it's possible that these trucks are getting so old now that they're all starting to suffer from age.
 

TJBaker57

Guru
Aug 16, 2015
2,000
Colorado
the four lights (plus N) would show up on the switch when I fired it up, but the lights would all go out and it would NOT shift.


Sounds like you experienced a C0550.

Screenshot_20211127-101639.png


Mine has done this but I just tap a few buttons on the phone, reading, recording, and clearing all codes for the TCCM and go on my way. If it were to recur I guess I would swap out the TCCM for one of the newer ones I have.

If you go looking for a TCCM I would look for one of these two numbers on the labels...

12590220
12577480
 

Maverickxeo

Registered Member
Original poster
Jan 25, 2021
40
Alberta, Canada
So I would like to update. I did change the motor several hundred KM ago. Since then, I have had NO issues - no codes, all the lights work, and it shifts as intended (I think it might shift *faster* in auto mode now - we have had a LOT of freezing rain here).
 

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