Ikeep getting a DTC P1635 reading about the 5 Volt Reference Circuit. I have replaced sensors but still get the error. I foun d a electrical diagram and troubleshooting guide for a 99 firebird but I'm sure that my 2003 Park Ave Ultra is different. I have searched but cannot find the diagram for the PA. Does anyone have a valid link?

Which sensors did you replace?

https://www.gmforum.com/showthread.p...ighlight=P1635

did you check the sensors connectors for 5v?

To answer both questions

I changed the MAP sensor and the EGR.
The reason I am looking for a link to the circuit diagram for the 2003 ParkAve Ultra is so I can find out which terminals between the PCM and sensors to check. The diag I have is for a 99 Firebird. The PCM for the buick has a lot more connections.

Thanks for the responses.

GREAT ! ! This is exactly what I was looking for. The one I had for the firebird only had 2 sensors.

Thanks !