P0A87

DTC P0A87

Diagnostic Instructions

* Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure. Initial Inspection and Diagnostic Overview
* Review Strategy Based Diagnosis for an overview of the diagnostic approach.
* Diagnostic Procedure Instructions provides an overview of each diagnostic category.

DTC Descriptor

DTC P0A87
- 14 Volt Power Module Current Sensor Performance

Circuit/System Description

The auxiliary power module (APM) current sensor is used for over current limitation (less than 150 A). The starter/generator control module (SGCM) monitors the current sensor to detect the failure of the APM current sensor circuit (performance monitor).

Conditions for Running the DTC

The engine is running.

Conditions for Setting the DTC

APM current limit.

Action Taken When the DTC Sets

* Stop PWM (MGU shutdown).
* APM PWM off.

Conditions for Clearing the DTC

* APM current (IR 1) is restricted by maximum current (IR HI or IR LOW)
* In case of Buck mode: IR 1 - IR HI is greater than 39 A for 25 ms.
* In case of Boost mode: IR - IR LOW is greater than 39 A for 25 ms.
* IR 1: APM current, IR HI: APM buck mode current limit +130 A.
* IR LOW: APM boost mode current limit (-130 A).
* APM output voltage (V14OUT) is greater than 7 volts and 42-volt output voltage (42OUT) is greater than 28 volts.
* Clears 30 seconds after cycle wakeup signal.

Diagnostic Aids

Possible internal failure at current sensor.

Circuit/System Verification

Caution: To help avoid personal injury, additional precautions must be taken prior to working on the generator control module or the generator starter. After removing the 36V battery cables from the generator battery, remove both engine wiring harness connectors from the generator control module. Wait at least 5 minutes and then remove the generator control module cover. Verify voltage levels at all 36V, 12V, and 3-phase connections, are less than 3 volts using a DMM before proceeding.

If DTC is current, replace the SGCM.

Repair Instructions

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