Circuit/System Description
The accessory DC power control module (APM) supplies 42 volts to the power steering control module (PSCM). The PSCM monitors the supplied
intermediate voltage to determine if it is within a valid operating range. Damage to components, and incorrect data may occur if the voltage is out
of range. The PSCM disables power assist and sets DTC C0895 if high or low intermediate voltage is detected.
Conditions for Running the DTC
The ignition is ON.
Conditions for Setting the DTC
C0895 03
Intermediate voltage is less than 40 volts.
C0895 07
Intermediate voltage is greater than 60 volts.
C0895 12
Intermediate voltage is less than 26 volts.
Action Taken When the DTC Sets
* The driver information center (DIC) displays the SERVICE POWER STEERING warning message.
* The PSCM limits the amount of steering assist if DTC C0895 03 is set.
* The PSCM disables steering assist if DTC C0895 07 or 12 is set.
Conditions for Clearing the DTC
* The DTC will pass when the intermediate voltage returns to the normal range.
* A history DTC will clear if the condition does not return after 100 consecutive ignition cycles.
Diagnostic Aids
* DTC C0895 will set if the APM has disabled the 42-volt conversion for any reason, such as a drive motor DTC. Diagnose any DTCs in the
APM that disable the 42-volt circuit before diagnosing DTC C0895.
* DTC C0895 may set if the engine stalls. Diagnose any engine stall DTCs in the ECM before diagnosing DTC C0895.
* DTC C0895 may set if the serial data is interrupted. Verify that all modules can communicate, and diagnose any U-codes before diagnosing
DTC C0895.
* The APM may disable the 42-volt conversion if the 12-volt battery has low voltage. The PSCM will set DTC C0895 as a result. Verify that
the 12-volt battery is fully charged before diagnosing DTC C0895.
* If there is low voltage on the 42-volt circuit only when turning the steering wheel, the power steering motor is drawing too much current.
This condition may set DTC C0895.
* As the front wheels roll over bumps while driving, the power steering motor will generate voltage spikes on the 42V circuit. The PSCM
contains a zener diode, to suppress any voltage spikes greater than 50 volts. The scan tool PSCM Intermediate Voltage parameter does not
update fast enough to view most voltage spikes. The scan tool APM 42V Circuit Maximum parameter will record and display the maximum
voltage on the 42V circuit during the current ignition cycle, including the voltage spikes caused by bump-steer. If the scan tool APM 42V
Circuit Maximum parameter is greater than 50 volts after driving on a bumpy road, then the diode in the PSCM is open. This condition may
set DTC C0895.
* When testing for voltage at the APM 42V connector X2, use care not to cause a short between the 42V+ terminal 2 and the grounded shield
which surrounds it. Use only the approved terminal probe, with the heat-shrink insulation in good condition, and only connect or disconnect
the terminal probe when the 42-volt circuit is OFF. Test the terminals on the APM itself, not the harness. Do not touch the DMM or test leads
while the ignition is ON.
Reference Information
Schematic Reference
Power Steering Schematics (See: Steering and Suspension/Steering/Diagrams/Electrical Diagrams)
