2010 Cadillac Truck Escalade EXT AWD V8-6.2L Page 1121

2010 Cadillac Truck Escalade EXT AWD V8-6.2L Page 1121

DTC Descriptor

DTC P0AB9

- Hybrid System Performance

Circuit/System Description

This vehicle does not use a 12V starter motor to crank the internal combustion engine. A much more powerful 300V drive motor generator located

within the transmission is utilized to crank the engine. The 300V drive motor generator can rotate the engine to operating speed (800 RPM) within

just a few hundred milliseconds. The HPCM can detect a condition where the engine is cranking but does not start or has stalled.

Conditions for Running the DTC

Drive motor generator 1 is cranking the engine.

Conditions for Setting the DTC

The HPCM detects that CKP engine speed has not risen above the commanded cranking speed indicating the engine has failed to start, or the

HPCM detects CKP engine speed has fallen below a specific minimum speed indicating the engine has stalled.

Action Taken When the DTC Sets

DTC P0AB9 is a Type A DTC.

Cranks But Does Not Start

When the ignition is turned to Crank, the HPCM will command drive motor generator 1 to rotate the engine. The drive motor will continue to rotate

the engine at a specific RPM until the engine starts and causes increased engine RPM. The HPCM will cease engine rotation if an increase in

engine RPM is not observed after several seconds. This function may have the appearance of a start/stall condition.

Engine Stall

If a stall occurs after a successful engine start, the HPCM will recognize the drop in engine RPM and command drive motor generator 1 to maintain

engine RPM in an attempt to restart the engine. Drive motor generator 1 will continue to rotate the engine until the HPCM commands it to stop. The

engine may be rotated for many minutes after the actual engine stall condition occurred and is typically stopped only after the hybrid battery state of

charge (SOC) gets too low. This function may have the appearance of a running engine.

Conditions for Clearing the DTC

DTC P0AB9 is a Type A DTC.

Diagnostic Aids

Any condition that causes the engine to stall and/or not start may set this DTC. Possible conditions include:

* Fuel conditions such as low level, low pressure, or contamination.

* Engine conditions such as low compression.

* Restricted exhaust or air intake systems.

Always inspect for DTCs that would cause an engine stall and/or no start condition. Because the hybrid system can rotate the engine at high RPM,

stall and cranks-but-does-not-start conditions act differently than a non-hybrid vehicle. Refer to Action Taken When the DTC Sets.

Circuit/System Verification

Turn the ignition to Crank. The engine should start and run.

If the engine fails to start, diagnose the engine system. Refer to Engine Cranks But Does Not Run (See: Powertrain Management/Computers and

Control Systems/Testing and Inspection/Symptom Related Diagnostic Procedures).

If the engine starts and runs the condition is intermittent.

P0ACB

DTC P0A9C-P0A9E, P0AC6-P0AC8, P0ACB-P0ACD, P0AE9, P0AEA, or P0AEB

Diagnostic Instructions

* Perform the Diagnostic System Check - Vehicle (See: Testing and Inspection/Initial Inspection and Diagnostic Overview/Diagnostic System

Check - Vehicle) prior to using this diagnostic procedure.