AWD light 1999 Bravada

[YooperJ]

My AWD lamp never comes on. When turning the key to run with engine off, nothing. I have no "check" of the lamp. Fuses are all good and there is power to the TCCM. Would this indicate a problem with the TCCM?

Thanks,

YooperJ

[Blue Bowtie]

I don't understand the concern. I mean, it's not like the iron range ever gets any snow or anything...

It may indeed indicate a problem. The "SERVICE AWD" lamp should turn on for about 1-2 seconds when the ignition is first turned on. If all the other warning lamps on the IP are turning on during bulb check, the GAUGES fuse is probably intact, as this also acts as the source for the AWD warning lamp. The ground for the lamp is via the TCCM through a splice pack (SP201) which connects to the Class 2 serial bus between the VCM and TCCM. The electronics in the IP decode the serial data to drive the lamp.

Is there evidence that the AWD is working? I know it's a little tough to determine with the 136 transfer case and fully automatic control system, but if you head over to your local Pat's IGA before they clear the lot, you might try spinning them a little to see of the rear axle is acting alone or if the front locks in.

If you have the ability, it may also be informative if you can raise the vehicle onto four stands, start it, and place it in gear. All four wheels should turn once the TCCM gets VSS input from the rear and quickly turn the TCM to lock the front driveshaft into drive.

If so, you might simply have a failed lamp. If not, you have some work to do before the REAL snow arrives.

We'll be waiting.

[YooperJ]

I had it parked for the summer as it is my main winter run-about. I also have a Saab 9-7 that is my main winter runner and a 1995 GMC 4x4 that is the workhorse so I do have alternatives. We had an early snow and when I accelerated, it spun the rear wheel and not the front. The other day I made room in the garage for a vehicle and brought it in to change the alternator and do some checking. The terminals on the TCCM had some corrosion so I cleaned them with a small screwdriver and electronic contact cleaner. I tried it last night the best I could and when I accelerated on a snow covered road, it did not spin out, but not sure how slippery it really was. Still no light and all other lights work. We got snow snow last night so I'll try it later and report back.

Thanks for the help,

YooperJ

[Blue Bowtie]

Originally Posted by YooperJ

... We got snow snow last night so I'll try it later and report back.

Yes, here too, but not as much (although it isn't done yet):



If the TCM is locking up the front driveshaft as it seems, you may only be fighting a failed lamp. That would be a good thing.

[YooperJ]

Tried the AWD today and no light but it is not working. Going to try and change the TCCM to see if that is the problem. It get power to the unit so, I think the corroded terminals I cleaned go further than the terminals. Will pull it apart to get a good look later this week.

More snow coming!!

YooperJ

[Blue Bowtie]

At least you don't have to dive under the vehicle to get to the control module. Good luck.

If your module has a blue connector shell (RPO Code NP1) it should be P/N 15741322.

If it has a green connector shell (NP4) it should be P/N 12577420 or 15748801.

If it has an orange connector shell (NP8)it should be P/N 12577412.

My best guess is that yours is green.

None of them are what I would consider a bargain. If you can find one at a salvage yard from a Bravada, Astro, Safari, or whatever to match your OEM part number, it might be worth checking out. I've also seen them on eBay for under $50.