ABS/Traction Control Problems

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erndog72

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Please help me figure this one out. For quite some time now my 2004 Montana has been turning on the ABS light, Trac OFF light, and Service Traction Control System message when the engine is started. At the same time the brake pedal vibrates violently and you can hear the traction control system kicking in. For a couple of months prior to this starting, the traction control would kick in randomly while driving.
My wife won't drive the van anymore because twice when she went to back out of a parking spot it did this and wouldn't stop until she smashed the brakes with all her might. The first time she almost hit another car. The second time she nearly ran over some people. Therefore, it is no longer a minor annoyance.

I had the ABS codes read with the following results (probably several weeks/months accumulation):
C1216 EBCM COMMAND PRESSURE RELEASE IS TOO LONG
C1225 LF EXCESSIVE WHEEL SPEED VARIATION
C1226 RF EXCESSIVE WHEEL SPEED VARIATION
C1227 LR EXCESSIVE WHEEL SPEED VARIATION
C1228 RR EXCESSIVE WHEEL SPEED VARIATION
C1254 ABNORMAL SHUTDOWN DETECTED
C1255 EBCM INTERNAL MALFUNCTION
C1277 REQUESTED TORQUE SIGNAL CKT MALFUNCTION
C1291 OPEN BRAKE LAMP SWITCH CONTACTS OPEN DURING DECELERATION
C1298 PCM CLASS 2 SERIAL DATA LINK MALFUNCTION
U1000 CLASS 2 COMMUNICATION MALFUNCTION

I am leaning toward a blown ECBM, but I would like others' opinions.
 
I will look into that, but it sure seems to be presented as a sales pitch more than experience.
 
Your first link did. The second one is much better. Actually, after doing some more research I feel it may likely be a C305 issue, since the gas gauge has been either failing high or low for about six months, too. That, as well as ABS and Traction system wires pass through this thing and it is notorious for issues from moisture.
 
As near as I can tell, the replacement for the c305 connector is an ACDelco PT1123. They are readily available, come with the leads, and are pretty cheap, even for the genuine ACDelco brand.
The only question I have is what is up with a single wire coming off one of my two smaller connections that doesn't seem to show up in any of the pictures of the PT1123 that I have seen.
 
I ordered both the PT 1123 and PT 1176 off amazon hopefully this will fix my problem just the 1176 was 70 bucks at autozone
 
Every PT1123 I see says "EXCEPT RR SEAT DVD PLAYER ENTERTAINMENT package(U32)". My van has that package. What part number do I use??
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OK, so I got the GM part# for the PT1123 C305 connector and ordered it. However, it only had two of the three gangs pinned out. Mine has three wires going to the third (2A, 2B, and 2C). I installed the unit, but will have to just hardwire the last gang. Now for my issue. The three wires are Lt Blu (Axle Actuator - Control), Pnk (Ignition 1 Voltage), and Black (Ground). However, the downstream connector only has the Lt Blu wire. What is up with the other two wires? I can't make heads or tails of the "wiring diagram" in the shop manual. I looked high and low for two loose wires underneath, including peeling back the wire loom to see if they pulled back. Nothing. Help?? Advice??
 
Yes, I did.
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Well, I finished replacing the C305 unit. I merely drilled a "pass-through" hole for the single wire in question and did a hard-wire connection. Nothing has changed. All of the symptoms are still there. One important symptom I forgot about - Usually, if I keep my foot hard on the brake while starting the engine, neither the ABS or the TRAC OFF light will come on, and they stay off until the next restart.
Ideas??
 
Your C1291 points to a switch problem. Have you had someone step on the brake pedal while you check if your brake lights come on?
 
Solved

After a week at the dealer, it is solved. Turned out to be the dreaded EBCM after all. Found a new one on Amazon for only $480. Dealer wanted $896 and wasn't even sure he could find one.
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I kinda suspected it all along, but didn't want to fork out the big bucks until everything else was exhausted.
 
ABS & Traction Control

Reading the post I see several others are having the same problem as I am with my 2005 Pontiac Montana. I have had mine in the Dealer for the past 3 weeks. They still have not found out why it turns the ABS light and Traction light on. They say it sets no codes,,,,,or they have not got it to set codes. So I'm not sure taking it to the experts (dealer) is the best either.
 
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