P109

PROM Checksum Circuit:

CIRCUIT DESCRIPTION
This diagnostic test monitors the Powertrain Control Module's (PCM) keep alive memory for a loss or unintended change of data. If such a condition occurs, Code P052/P109 will set.

TEST CONDITION
Test continuously.

FAILURE CONDITION
Keep alive memory checksum does not match previous checksum.

ACTION TAKEN
None.

NOTES ON INTERMITTENTS
If the battery has been disconnected for any reason Code P052/P109 will set.

The PCM keeps a running check on the memory; if memory changes it resets.

Code P052/P109 may set while keying "OFF" in diagnostics. If the Instrument Panel Cluster (IPC) is sending new information to the PCM when the ignition is turned "OFF," the PCM may think it has been switched, causing a reset.

DIAGNOSTIC CHECKS
Codes P052 and P109 indicate that the "Long Term" memory in the PCM has been reset.

This will be the case whenever battery power is removed from the PCM (i.e., disconnecting battery cables, disconnecting PCM connector, etc.). This code should be "cleared" from memory after restoring the PCM's power supply.

If codes P052/P109 are accompanied by complaint of engine quit, stumble, Malfunction Indicator Lamp (MIL) flashing, or other stored codes, check for an intermittent loss of power (CKT 840) or ground (CKT 451) to the PCM. Manipulate wiring and connections with the engine running, remove and reinstall the PCM connectors and ensure that they are latched properly.