69gto96z

iTrader: (13)

So I got my car tuned last week after the cam/Walbro 255/nitrous install. To me, it is a coincidence that this issue happened the same day. Trailered the car to and from the tuner. I now have a ABS INOP light, complaining about the left rear sensor, as well as a P1639, 5 Volt reference B2.

I have checked the voltage at the TPS, 5v. Checked voltage at the high side A/C sensor, getting about .082. Checked voltage at the Fuel Pressure Sensor on the tank, getting 0. Checked the A/C sensor with the fuel sensor unplugged, same, .082 volts again. I have checked all of the wires at the bulkhead, as well as the wires going to the left rear ABS sensor, all look good.

I am completely stumped. The car runs great, all gauges work fine. My first thought was maybe i cut a wire with a strap while loading onto the trailer on accident, but have found nothing.

My next thought is the wires from the bulkhead on the interior. My nitrous bottle is mounted on the hump. I came across some pictures of my TA with the carpet out, and noticed that the wires from the bulkhead run along the tunnel inside the car. I am thinking I may have pinched a wire somehow installing the bottle mount.

Does anybody know what wires run through the interior to this bulkhead? Any and all help is greatly appreciated. The SES and ABS light are aggravating. I plan to delete ABS, so I am not too worried about fixing it, but the check engine light has go to go!

RockinWs6

I would contact the tuner before doing anything. At least save this tune and then swap in a stock tune to see if the trouble goes away.

G8One2

Was it dyno tuned? If so, check or reconnect the left rear wheel speed sensor. They most likely disconnected it during the dyno run to keep the abs and traction control from activating during the run, and may have forgot to plug it back in. That'd be my guess...

69gto96z

iTrader: (13)

Yes it way dyno tuned, but it threw the codes right before it got on the dyno. It didn't have these codes before the nitrous install. I put about 50 miles on the car with the cam on the stock tune, before swapping injectors and installing the nitrous kit. After that was done, the car ran for less than about 2 minutes.

I checked the connection back at the wheel sensor, unplugged it, and removed all of the plastic loom to make sure the wires were good, put it all back on and plugged it back in.

I would like to check to make sure the pcm is reading OL from the 5v reference pins, but i do not know which ones they are, or how to do it properly since the plastic cover is over the wires.

G8One2

I could be wrong, but i dont think your wheel speed sensor gets a 5v ref. They are just a magnetic pick up that show a PWM to the ABS module. You could check resistance between the 2 pins going to the wheel speed sensor, it should show some resistance (under 5 Ohms) and should not be an open circuit. If it is open, then you would need to replace the wheel speed sensor. I know on big trucks like Semi's have a different system in which they generate a voltage when the wheel is spinning, but i dont think cars have that type of system generally.

69gto96z

iTrader: (13)

No, ABS does not have a 5 volt reference. I will check resistance too. I think my issue is going to lie in the wiring around the bulkhead, as the 5v reference wire and abs sensor running through that connection threw codes at the exact same time.