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 control modules; the hybrid powertrain control module, 14 volt power module and the drive motor control module. These modules are non serviceable and are part of the generator control module.

The eAssist hybrid system has an electric machine 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 reading over serial data and compares that value to the drive motor 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, or P0336 are not set.

Conditions for Setting the DTC

The hybrid powertrain control module detects a difference between the engine and the drive motor speeds of greater than 1000 rpm.

OR

The hybrid powertrain control module detects a difference between the engine and the drive motor speeds 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.

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 drive motor speed.
* Inspect the drive belt for cracks and oil contamination.
* Test drive the vehicle through the different modes of operationand performing Autostop and Autostart cycles. Accelerate up to 50 mph and brake moderately, and listen for any audible belt squeal.

Reference Information
Schematic Reference

Hybrid Energy Storage Schematics [1][2]Electrical Diagrams
Description and Operation

* Starter Generator Description and Operation Starter Generator Description and Operation
* Generator Control Module Description and Operation Generator Control Module Description and Operation
* Hybrid Modes of Operation Description Hybrid Modes of Operation Description

Electrical Information Reference

* Circuit Testing Circuit Testing
* Connector Repairs Connector Repairs
* Testing for Intermittent Conditions and Poor Connections Testing for Intermittent Conditions and Poor Connections
* Wiring Repairs Wiring Repairs

DTC Type Reference

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

Circuit/System Testing

1. Inspect the condition of the drive belt tensioner.

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

2. Inspect the condition of the drive belt.

• If the belt is not OK, replace the drive motor 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 Starter Generator Replacement for drive motor replacement.
* Drive Belt Replacement (LUK) Service and Repair
* Drive Belt Tensioner Replacement (LUK) Service and Repair