Fault Condition: The Engine Retarder Percent code will set when the Engine Management System (EMS) Module has lost the Engine Retarder Percent signal from the Vehicle Electronic Control Unit (VECU).

Possible repairs:

1) Verify that code PPID 86 is set. If code PPID 86 is not set, wiggle the harness and connectors to try to set the code. Visually inspect the VECU connectors and wires for poor connections.
2) Turn the ignition key OFF and connect a diagnostic computer. Turn the ignition key ON. Use the diagnostic computer to attempt to communicate with the Vehicle Electronic Control Unit (VECU).
If communication can be made with the Vehicle Electronic Control Unit (VECU), the fault may be intermittent, wiggle the harness and connectors to try to set the code. If fault in the harness is found, repair or replace the harness.
If there is NO communication with the Vehicle Electronic Control Unit (VECU) via the diagnostic tool, go to the Trouble Shooting Procedure for the Data Lines.