2003 8.1 Kodiak, Code P0650

[Maynard Tolman]

I'm trying to work through this code. MIL stays on all the time. No other codes. Did a 'check' of the IPC and can turn on all lights in the IPC and turn them off with my Launch scan tool. Once exiting the test, the MIL is still on. I used a flow-chart for a C3500 as I can't find one for the 4500 and the MIL is supposed to be turned on via a signal on pin 46 of ECM Connector #2. Wiring of this connector looks just like the wiring diagram for the 3500. When removing the C2 ECM connector the light says on in the dash. When I unplug the C1 connector the light will go out. So, the MIL is being turned on by something in connector #1. I was wondering if anyone on here has any ideas. Thank you,

[asilverblazer]

I would disassemble the IPC and look for shorts. Some careful probing with a multimeter ought to be able to track it down. 

 

I suspect the C1 connector has an 'always on' circuit in it that is back feeding the MIL circuit and thus throwing the code.

 

I don't have a diagram to refer to to try narrowing it down further.

[asilverblazer]

2 minutes ago, asilverblazer said:

I would disassemble the IPC and look for shorts. Some careful probing with a multimeter ought to be able to track it down. 

 

I suspect the C1 connector has an 'always on' circuit in it that is back feeding the MIL circuit and thus throwing the code.

 

I don't have a diagram to refer to to try narrowing it down further.

See this link...

 

https://www.gmupfitter.com/wp-content/uploads/2021/05/2004_MD_CSeries.pdf

[mjm-1957]

I hope these load correctly.

Document ID 721284.htm Document ID 792612.htm

[asilverblazer]

Did you work through those? What did you find?