P1A88

DTC P1A88

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 P1A88
- 42 Volt System Performance

Circuit/System Description

The accessory DC power control module supplies the energy that flows between the high voltage, 300 volt, DC and intermediate voltage, 42 volt, DC to support the electric power steering. The accessory DC power control module receives a 42 volt enable command from the hybrid powertrain control module over serial data. 42 volt accessory DC power module functions will run only when the 42 volt accessory DC power control module enable is active through serial data.

The accessory DC power control module continuously monitors the status of its 42 volt circuitry. When the ignition key is first turned to RUN, some diagnostics are performed on this circuitry. When the engine is started, and the 42 V enable command is received by the accessory DC power control module, additional diagnostics are run.

Conditions for Running the DTC

* Ignition voltage is 7 V and no more than 16 V.
* The accessory DC power control module runs a portion of the diagnostics for this DTC at Accessory/Ignition On.
* The accessory DC power control module runs additional diagnostics when the 42 volt output is commanded on.

Conditions for Setting the DTC

* An external condition has caused an accessory DC power control module 42 volt malfunction,
OR
* The accessory DC power control module has detected an internal malfunction.

Action Taken When the DTC Sets

* DTC P1A88 is a Type C DTC.
* The accessory DC power control module will shutdown 42 volt conversion.

Conditions for Clearing the DTC

DTC P1A88 is a Type C DTC.

Diagnostic Aids

This DTC can set as a result of conditions external to the accessory power control module. Before attempting to diagnose a history DTC, ensure that none of the following conditions have occurred:

* High voltage contactor relays opening any time the accessory DC power control module is doing 42 volt conversion.
* The high voltage system greater than 390 volts or less than 216 volts during 42 volt conversion. Extreme cold weather conditions may occasionally cause the high voltage system to be greater than 390 volts.
* The 12 volt circuit was less than 6.7 volts during 42 volt conversion.
* A short circuit condition on the 42 volt circuit which causes the accessory DC power control module to produce greater than 60 amps.

Reference Information
Schematic Reference

Hybrid Controls Schematics Hybrid Controls Schematics
Connector End View Reference

Component Connector End Views Connector Views
Description and Operation

Drive Motor Generator Control Module Description and Operation Drive Motor Generator Control Module Description and Operation
Electrical Information Reference

* Circuit Testing Circuit Testing
* Testing for Intermittent Conditions and Poor Connections Testing for Intermittent Conditions and Poor Connections

DTC Type Reference

Powertrain Diagnostic Trouble Code (DTC) Type Definitions Powertrain Diagnostic Trouble Code (DTC) Type Definitions
Scan Tool Reference

Control Module References Control Module References for scan tool information

Circuit/System Verification

1. Verify there is no other hybrid DTCs set.

• If other Hybrid DTCs are set, refer to Diagnostic Trouble Code (DTC) List - Vehicle Diagnostic Trouble Code (DTC) List - Vehicle.

2. Ignition ON, engine OFF, observe the scan tool battery energy control module contactor system status parameter. The status should display closed.

• If not the specified value, refer Symptoms - Hybrid Controls Symptoms - Hybrid Controls.

3. Verify that DTC P1A88 is not set as current.

• If the DTC is set as current, replace the K1 accessory DC power control module.

4. Ignition OFF, disconnect the X2 harness connector at the K1 accessory DC power control module.
5. Ignition ON, engine OFF, command the accessory DC power control module Intermediate Voltage Control ON with a scan tool. Test for 42V between the K1 accessory DC power control module X2 terminal 1 and 2. The reading should be between 40 V and 44 V.

• If not within the specified range, replace the K1 accessory DC power control module.

6. Ignition OFF, connect the X2 harness connector at the K1 accessory DC power control module.
7. Ignition ON, engine OFF, command the accessory DC power module Intermediate Voltage Control ON with a scan tool. Verify the 42V circuit parameter between 40 V and 44 V.

• If not within the specified range, replace the M38 power steering assist motor.

Repair Instructions

Perform the Diagnostic Repair Verification Verification Tests after completing the diagnostic procedure.

* Power Steering Assist Motor Replacement Service and Repair
* Control Module References Control Module References for Power Steering Motor Control Module or Accessory DC Power Control Module replacement, programming, and setup