Electrical Distribution Question


amphib72
07-02-2015, 05:53 AM
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 MALFUNCTIONI was leaning toward a blown ECBM.

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.

Now for the electrical question:
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??
By the way, the problems still exist.
http://www.pontiacowners.com/pontiac/images/smilies/confused.gifhttp://www.pontiacowners.com/pontiac/images/smilies/frown.gifhttp://www.pontiacowners.com/pontiac/images/smilies/frown.gifhttp://www.pontiacowners.com/pontiac/images/smilies/frown.gifhttp://www.pontiacowners.com/pontiac/images/smilies/frown.gifhttp://www.pontiacowners.com/pontiac/images/smilies/frown.gifhttp://www.pontiacowners.com/pontiac/images/smilies/confused.gif

Tech II
07-02-2015, 02:54 PM
If you clear all the codes, which one comes back first?

C305....are you talking about the connector, underneath the van, driver's side, approx, where the back edge of the driver's seat is? If yes, were the contacts corroded?

amphib72
07-03-2015, 02:40 PM
Yes. No, they weren't.

Tech II
07-04-2015, 07:20 AM
The only reason to replace that harness, is if they were corroded....

amphib72
07-07-2015, 05:26 AM
I wasn't sure if perhaps some of the contacts were no longer making good tight connections, so I replaced it anyway.

amphib72
07-07-2015, 05:28 AM
One thing I forgot to mention is that if I start the engine with the brake applied I don't get the trouble lights or the pedal vibration. Ideas??

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