Powertrain Diagnosis

Wiring Diagram:

P0562- SYSTEM VOLTAGE LOW
The ECM monitors vehicle system voltage by monitoring the voltage on circuit 2740 coming from the main relay. which is referenced to the ECM case ground. Each of the three main relay pins going into the ECM are tied together internally in the ECM. When ignition voltage is present at the ignition 1 input to the ECM (circuit 339), the ECM will command the main relay On by supplying ground to the main relay coil circuit. When the relay is energized, battery voltage should be present on each circuit 2740 at the ECM. DTC P0562 will set if the ECM detects lower than normal system voltage on circuit 2740 for a certain length of time after the engine has been running when the main relay has been commanded On.

DTC PARAMETERS
DTC P0562 will set if system voltage measured at the ECM main relay voltage circuit 2740 is less than 9.0 volts when:
^ Condition exists for longer than 0.2 seconds
^ Main relay is commanded On because the ECM detected ignition voltage present at the ignition 1 input to the ECM
^ Engine run time is greater than 3 minutes
^ Vehicle speed is present

DTC P0562 diagnostic runs continuously once the above conditions have been met.

P0562 is a type D DTC

DIAGNOSTIC AIDS
IMPORTANT: If a generator L-terminal DTC is also set, diagnose that DTC first. A fault in the charging system may set this DTC.

DTC P0562 indicates that the battery voltage supplied through the main relay to circuit 2740 was low. which most likely indicates a charging system problem.

To locate an intermittent problem, use Scan tool to monitor BATTERY voltage with engine running at 1300 rpm. With all accessories On or all accessories Off. charging voltage should be in the range of 12.5-15.5 volts.

Compare BATTERY voltage on Scan tool with the actual voltage measured at the battery with a DVOM. If readings do not fall within +/- 0.2 volts, check battery cables and the ECM case ground bolts for tightness and for battery terminal corrosion.

Perform a charging system test. Refer to "Starting and Charging Section".