2004 Tahoe/Viper 4606 case review ACC outputs

This install was done in a 2004 Chevy Tahoe. Basic r/s install, the owner did not want any kind of horn/sirens connected to unit.

Main harness 6 pin
H/1 12v constant
H/2 Ground
H/5 Park light (-) to bcm

Door lock 3 pin
1 To GMDLBP unlock
3 To GMDLBP lock

R/S 8 pin
1 12v at IGN harness
3 to IGN 2 at IGN harness
4 12v at IGN harness
5 to START at IGN harness
6 to ACC at IGN harness
7 12v at IGN harness
8 to IGN1 at IGN harness

Aux/shutdown 24 pin
5 to GMDLBP gwr
9 to hoodpin
12 tach wire at cluster
13 Ground
15 to gmdlbp door output -
20 to brake switch
23 to 85 of acc2 relay

ACC2
87/86 12v at IGN harness
30 ACC2 at IGN harness
85 Aux harness pin 23
1n4007 85/86

GMDLBP
brown gwr to aux harness 5
green to 3 pin #3
blue to 3 pin #1
violet to obd2
pink/white to aux harness #15
red 12v constant
black ground


Two weeks or so after the install, the following symptoms were present:

1-ABS light/service stabilitrac message during r/s, light/message went out after key takeover
2-Vehicle battery dead after sitting 2-3 days
3-Antenna LED would not flash when r/s active


Diagnosis:

1- BCM would show ACC:INACTIVE during a remote start and show ACC:ACTIVE after key takeover.
   Note, in this truck the BCM calls orange ACC "IGN 3" and brown ACC2 "ACC".
   Pin 23 of aux harness not grounding acc2 relay during remote start. Diode intact.
2- Key off draw measured 380mA after tahoe hvac/bcm went to sleep.
   Further testing found pulling fuse from RED / black of 8 pin connector brought draw to roughly 10mA.
   As soon as fuse was installed, had power on pin 6 of 8 pin connector.
   When the fuse was installed I could hear an on board relay click inside the brain.
   BCM would show IGN3:ACTIVE at all times when fuse installed.
3- I had no responce from the antenna. No programming or LED. The antenna still responded to key fobs.
   This was a fluke - when I probed pin 23 with piercing probe I accidentally cut through the wire. The LED immediately came on and could go through programming.

I double checked my connections and was able to warranty a new brain.
New brain install and programming went smooth.
It's been several weeks since the brain swap and the owner has reported no issues.
I wish I had the resources to get an "official" root cause but if I cracked the brain open I couldn't have returned it.
And if I had cracked the brain open I wouldn't know what to do anyway.

Sorry for the novel but this forum has helped me a ton over the years and I wanted to give something back.

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2003 Trailblazer LT
2007 Envoy SLT

Sounds like it worked out in the end. The only thing that would be a concern on those vehicles is drawing too much power through too small of a fuse. I prefer DEI units in these trucks as the loads are more evenly distributed. Then of course the ground..as these trucks age out the factory grounds that were poor when new are getting worse by the day. Really have no choice but to ground to the painted body (paint scraped away obviously) anymore.

On the other hand electronics fail. Regardless of brand or maker, or anything else. They are still made as cheap as possible to maximize profit. I wouldn't sweat it too much unless you have a rash of bad units. Consider it a fluke and as long as the customer has what they paid for everyone can forget about it.

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To master and control electricity is perfection. *evil laugh*