fixbroke

Hi gents.
I've got an interesting problem that I'm hoping someone here might have some experience with. I've been getting a "service stability system" message in my V for a while, and I finally got my VCX Nano working with Tech2Win so I could read the code and diagnose the problem.

The codes were C0136 (Base Brake System Pressure Circuit) and C0137 (Base Brake System Pressure Circuit Range/Performance), and I was seeing 4.92 volts from the brake pressure sensor.

I unplugged the sensor from the harness and checked the voltage again on Tech2Win, and it was still reading 4.92 volts. Strange! I put a multimeter on the harness connector and sure enough, I had 4.92 volts from both the signal and the +5 reference wire to the low reference wire (with the sensor unplugged), but no continuity between the signal and +5 ref wires.

Looking at the wiring diagram, it seemed that the problem must exist within the EBCM so I pulled it out and had a look. There was evidence of some moisture getting in there, so I thought I had surely found my culprit. I ordered a used one off Ebay and swapped it in, only to find (frustratingly) that the problem persisted.

I've been poring over the wiring diagram to figure out how the signal wire is getting a constant 5 volts when not connected to the sensor, but I'm out of ideas. Does anyone have some guidance on what to look for? Any help would be much appreciated!

fixbroke

The car is an 05 CTS-V with ~120k mi.

Here are the relevant sections from the wiring diagram. We're looking at wires 11, 12, and 17 (B13, B14, and C10 at the EBCM connector).

It's worth noting that the wire run from the sensor to the EBCM is very short (less than a foot), and I couldn't see any harness damage, so I'm skeptical that the signal wire has shorted to another +5 volt reference.