07 G6 4 door. This car has active ABS sensor so most of the diagnostics you read on line will not work. The troubleshooting for active sensors if quite different than for passive.
On active sensors one of the wires going to the sensor will have close to battery voltage. The other wire is the return signal wire and in my case gave a reading of abouut .06 V.
For any one interested I'll give you a simple trouble shooting procedure. Even if you are old and slow like me you can do this in less than an hour. Jack up both wheels on the end of the car where the problem sensor is, assuming you have used a code reader to locate which wheels (s) it is. Remove both tires if you want to. Don't forget to use jack stands.
In my case it was left rear that had the issue. Since I had a pig tail and a spare battery the rest was easy. First I determined which was the power wire going to both wheels. I used a multi-meter and a long jumper from the car battery's (not the spare on) negative post back to where I was working. This ensured a good ground. I checked both sockets on the left and right right wiring harness with them unplugged from the sensors. This told me which wires were which. Key needs to be on.
To make sure the left sensor was actually doing anything I plugged the pigtail into the sensor and connected the wire that was on the power side if the sensor to the positive post of my spare battery. You need an LED testlight for this, one with a light bulb will not work. The test light is connected from the signal wire on the pigtail to the spare batteries negative post. If the sensor is working the led will light up and change intensity as the wheel is rotated. This will not confirm a good or bad sensor but will tell you if the sensor is at least sending a signal.
Since my sensor was sending a signal it was off to the next step. I ran a jumper from the pigtail power wire to the right side wiring harness's power wire and a jumper between the pigtail signal wire and the right side harness signal wire. Cleared the codes and rescanned. Scan came back with a left side code. This was to be expected since the left side harness wasn't connected to anything. This also meant the the left wheel sensor was working correctly and the problem most likely was a broken wire somewhere in the left sensor harness.
Next I moved the pigtail to the right wheel sensor and connected the jumpers to the corresponding wires on the left harness. Cleared the code and rescanned. Now I had a right and left side code. This confirmed the problem was in the left harness.
There is a connector under the car on the right side. It's in the area of the rear door hinges. I found a broken wire right at the plug on the infeed side of the connector.
Before fixing the wire i wanted to check for other possible issues with the harness. I moved the pigtail back to the left wheel and connected the jumper to the broken wire and pigtail power wire. The pigtail signal wire was connected to the left signal wire at the connector. They're color coded. Cleared the codes and crossed my fingers that all I would get back was a right side code. And that's what come back. Fixed the wire and all is good.