V1 Dash not working properly

[dastrups]

I have noticed several things not working properly on my dash. Speedo, mileage, and coolant temps not showing at all. Rpms and other things work fine. I have a brand new coolant temp sensor and a brand new sensor on the transmission for the Speedo. Any ideas?

 

[Gtstorey]

Did you check the resistance on the VSS? My original and the new one on the transmission that I bought from DF were both out of spec. The replacement I bought was in spec. I don’t know for sure that it was a problem since it turned out to be a bad stepper motor on the speedometer.

I would bet you have a wiring problem though and need to start tracing. Probably two different issues though since the data wiring seems to be working.

 

[Gtstorey]

A bad VSS might should show a code although I’m not sure? Tracking down the speedometer trouble shooting in the service manual is a little iffy since it is several different sections.

 

[Ark :D]

Mileage comes from the BCM, so if you're not seeing mileage in your cluster, to me, it would indicate a problem in the wiring between your BCM and cluster. Not very helpful, I know...

 

[Gtstorey]

On some of the transmissions, I think the reverse sensor and the VSS have the same connector so make sure they aren’t swapped.

 

[Ross]

Is the GM LAN working at the OBDII port? (Can you pull the engine codes)
This test will tell us if the data is flowing from the PCM & BCM, to the OBDII port.

 

[dastrups]

I get P0119 and P0128. But the engine and sensors are all brand new. Even the fuse box is new. I would say my wiring is probably goofed up somewhere. I don’t really have the expertise to know what to look for.

 

[Gtstorey]

What donor? If it’s one of later ones I can post the diagnostic steps.

Both codes are engine coolant temp issues.

 

[dastrups]

2008 Chevy cobalt ss

 

[Gtstorey]

Since the first code is an intermittent signal, let’s start with the wiring diagram and few checks. Inspect the wiring from the sensor to the ECM. Especially the connector on the sensor. If that checks out good check the resistance across the sensor to the table included. If that checks, you should get pretty close to the same readings at the ECM connector. If I need to walk you through it a little more let me know.

 

[dastrups]

I am a special kind of stupid. After doing some searches on the cobalt forum I found someone as dumb as me. I had switched the Speedo and coolant temp plugs. Changed them and everything works great haha. Thank you guys!