GMC Troubleshooting Questions? Ask a Mechanic for Answers
Did you pull speed sensors from transfer case?
The site is definitely real. Do you have access to an ohmmeter?
Connect meter leads across each sensor (one meter lead to each terminal on the sensor) Should read in the range of(###) ###-####ohms. Another test you can do is to swap around the position of the two rearward sensors to see if the speedo starts working again.
The money you paid stays in your account. None of it is paid to the expert until you are satisfied with the service.
When you lose speed signal, the computer will not shift the transmission. Also no speed signal to instrument cluster for speedometer. No speed signal to ABS computer so abs and brake warning lights will be on. Also cruise control will be inoperative. Most common problem is a failed sensor. Since you have them all out and have no way of knowing which one was in the position of vehicle speed sensor, best to take ohmmeter reading and replace the one that reads bad.
One is vehicle speed. One is output speed for transfer case control module, one is transfer case input speed.
Left (drivers side) rear should be the one in question.
Set on Ohms. Meter should automatically adjust scale.
Good morning. I have seen this problem numerous times before. Check the picture attached. The main sensor for speedometer and computer operation for shifting, abs, etc. is highlighted. Wire colors for this sensor are Purple/White and Light Green/Black.
Try reinstalling the sensors. Install the new sensor to the drivers side rear location and test drive to see if the problem is still present. Let me know.
Follow wiring harness up towards rear of transmission. Check connector there to make sure it is fully plugged in.
You can take ohmmeter reading at the PCM connector. If you want to to this, let me know and I will get you the connector diagram of the PCM.
If you are satisfied with my service then we are done. Certainly let me know if you need any assistance in the future. Glad I could help you.