Circuit/System Testing

WARNING: This page is about a different car, the 2023 GMC Sierra 3500 HD and 2023 GMC Sierra 2500 HD. However, it is still accessible from the selected car via links, so may be relevant.

NOTE:

This Diagnostic Procedure Will Only Diagnose Factory Installed Components. It Will Not Diagnose Upfitter Provided Equipment. If The Cover For The Frame Rail X176 Provisional Connector, Which Includes A Jumper Wire, Is Removed DTC P251E May Set.

Ignition Off And All Vehicle Systems Off, Disconnect The Harness Connectors At The K44 Power Take - Off Control Module And Connector X3 At The K20 Engine Control Module. Remove The Frame Rail X176 Provisional Connector Cover. It May Take Up To 2 Min For All Vehicle Systems To Power Down.
Test For Less Than 1 V Between The K44 Power Take - Off Control Module Connector X2 Terminal 28 And Ground.
- If 1 V Or Greater
  Repair The Short To Voltage On The Circuit.
- Go To Next Step: If Less Than 1 V
Test For Infinite Resistance Between The K44 Power Take - Off Control Module Connector X2 Terminal 28 Circuit And Ground.
- If Less Than Infinite Resistance
  Repair The Short To Ground On The Circuit.
- Go To Next Step: If Less Than 2 Ω
Test For Less Than 2 Ω End To End At The K44 Power Take - Off Control Module Terminals Listed Below:
- K20 Engine Control Module Connector X1 Terminal 25.
- K44 Power Take - Off Control Module Connector X2 Terminal 28.
- If 2 Ω Or Greater
  Repair The Open/High Resistance In The Circuit.
- Go To Next Step: If Less Than 2 Ω
Test Or Replace The K20 Engine Control Module.
Verify DTC P159C Does Not Set When Operating The Vehicle Within The Conditions For Running The DTC.
- If The DTC Sets
  Replace The K44 Power Take-Off Control Module.
- Go To Next Step: If The DTC Does Not Set
All Ok.