P0A90

DTC P0A90

Diagnostic Instructions

* Perform the Diagnostic System Check - Vehicle Diagnostic System Check - Vehicle prior to using this diagnostic procedure.

* Review Strategy Based Diagnosis Strategy Based Diagnosis for an overview of the diagnostic approach.

* Diagnostic Procedure Instructions Diagnostic Procedure Instructions provides an overview of each diagnostic category.

DTC Descriptor

DTC P0A90
- Drive Motor Performance

Circuit/System Description

The generator control module also called the starter generator control module is comprised of the following three control modules; the hybrid powertrain control module, 14 volt power module and the drive motor control module. These three control modules are non serviceable and are part of the generator control module.

The eAssist hybrid system has a starter generator also called a drive motor. The starter generator is mounted to the front of the engine and is mechanically connected to the crankshaft pulley by a serpentine belt.

The hybrid powertrain control module receives an engine RPM signal over serial data and compares that value to the starter generator rpm received from the drive motor control module. The hybrid powertrain control module uses a ratio of these two speeds to determine if the drive belt is missing or slipping.

Conditions for Running the DTC

* Engine is running.

* The system voltage is at least 9.5 V.

* DTCs P0A3F, P0A40, P0B03, P0B0D, P0335, P0336, P0C19 or P1E0A are not set.

Conditions for Setting the DTC

The hybrid powertrain control module detects a speed difference between the engine and the starter generator of greater than 1000 rpm.

OR

The hybrid powertrain control module detects a speed difference between the engine and the starter generator of greater than 500 rpm multiple times on two consecutive ignition cycles with a Engine Off time of 30 minutes between key cycles.

Action Taken When the DTC Sets

DTC P0A90 is a Type A DTC.

Conditions for Clearing the DTC

* DTC P0A90 is a Type A DTC.

* The hybrid powertrain control module detects a speed difference between the engine and the starter generator of less than 500 rpm.

Diagnostic Aids

* The ratio between the crankshaft and the drive motor speeds is 2.3 to 1. When using a scan tool to determine belt slip the engine (crankshaft) RPM value must be multiplied by 2.3 to approximate the starter generator speed.

* Inspect the drive belt for cracks and oil contamination.

* Test drive the vehicle through the different modes of operation, performing Autostop and Autostart cycles. Accelerate up to 50 mph and brake moderately, and listen for any audible belt squeal. If drive belt noise is noticed check the drive belt tensioner assembly for proper operation and installation.

Reference Information

Description and Operation

* Starter Generator Description and Operation

* Generator Control Module Description and Operation

* Hybrid Modes of Operation Description

DTC Type Reference

Powertrain Diagnostic Trouble Code (DTC) Type Definitions Powertrain Diagnostic Trouble Code (DTC) Type Definitions

Circuit/System Testing

1. If drive belt noise was noticed on an AutoStart, refer to Drive Belt Tensioner Diagnosis Testing and Inspection.

2. Inspect the drive belt for cracks, wear and contamination.

• If the belt is not OK, replace the drive belt.

3. If the DTC resets, replace the A15 starter generator.

Repair Instructions

Perform the Diagnostic Repair Verification Verification Tests after completing the repair.

* Starter Generator Replacement

* Drive Belt Replacement Service and Repair

* Drive Belt Tensioner Replacement Service and Repair