Circuit/System Verification

WARNING: This page is about a different car, the 2008 GMC Yukon and 2008 Chevrolet Tahoe. However, it is still accessible from the selected car via links, so may be relevant.

Inspect for ECM P0335 or ECM P0336. With the engine running, observe the hybrid powertrain control module (HPCM) Engine Speed parameter with a scan tool. The parameter should display the current engine speed, matching the tachometer and/or the ECM Engine Speed parameter.

If ECM DTCs P0335 or P0336 are set, diagnose them prior to diagnosing the HPCM DTC.
If the HPCM Engine Speed parameter displays a value other than the current engine speed, continue with Circuit/System Testing.