Control Module: Testing and Inspection

Fig. 1 Internal Relay Circuit Schematic:

Diagnostic Code: P O6O5

Internal Control Module ROM Test Error
On each power-up, the engine control module (ECM) accesses its Electrically Erasable Programmable Read Only Memory (EEPROM) where it has stored DTC codes which have been flagged; freeze frame data logged at the time of those flaggings; and adaptive fuelling values. If a retrieved parameter does not correspond to what the ECM knows to being a "sensible" value, then it will re-access that memory location up to two more times to try to obtain a such a value.

If a "sensible" value for a parameter accessed from EEPROM is not received after three attempts then the fault code is stored and the MIL Lamp illuminated.

During initialization and operation the background diagnostics run a checksum on the data in the EEPROM. The check-sum is performed on 20 bytes each programme cycle and the results are summed to achieve a complete checksum. If a fault is already logged then a complete checksum will be performed during initialization. When a checksum error is detected, the transmission control module (TCM) will adopt the default function and store this fault code.

If this fault is permanently flagged, then the TCM should be replaced taking care to obtain the correctly programmed variant.