V1 Bouncing Tachometer and slight blinking of cluster???

[viperbmw69]

I am having an issue with the Cluster Tach bouncing it boucing from like 1k rpm to 3k back to 2 back to 1k and then 3k and keeps doing it. This is Tach only the engine is idling smooth. Also the cluster is going blank and back blank and back. Seems like an electrical issue sure but I have not idea where to look ANy help

 

[Joebob]

Have you pulled any DTC codes. That can help. Usually the gage cluster freaks out when there is a communication fault to the BCM. This would be the tan/black and tan twisted pair that run through the system. Check your grounds first, in the back and under the hood. make sure they are clean and tight and the wires themselves are not corroded. Next would be to check the network health through the OBD2 port. It could be loose connectors to the BCM/ECM/power steering or loose pins within the connectors. Disconnect the battery before unplugging those to avoid messing with the computers.

Good luck.

Joe

 

[Joebob]

This is what I use to check the CANbus.

Joe

 

[viperbmw69]

Have you pulled any DTC codes. That can help. Usually the gage cluster freaks out when there is a communication fault to the BCM. This would be the tan/black and tan twisted pair that run through the system. Check your grounds first, in the back and under the hood. make sure they are clean and tight and the wires themselves are not corroded. Next would be to check the network health through the OBD2 port. It could be loose connectors to the BCM/ECM/power steering or loose pins within the connectors. Disconnect the battery before unplugging those to avoid messing with the computers.

Good luck.

Joe

What voltage should I see on the tan tan/blk wires? Is it 12 everywhere? I think I seen 6ish.

 

[Desert Sasqwatch]

The tan black/tan or green black/green twisted pairs should not have 12 or even 6ish volts on them. These circuits run on a PWM 2.5 volts signal and not a voltage level. If you are seeing a constant DC voltage, then something is wired incorrectly or shorted.
SECTION ‘X’ CONTENTS (aeswave.com)

 

[Ross]

The GM high speed LAN is +3.5 volts on the tan wire to indicate a binary 0, and +2.5V to indicate a binary 1.
The low line is and +1.5V to indicate a binary 0, and +2.5V to indicate a binary 1.