Circuit Description
The Program Read Only Memory (PROM) is a removable computer chip that is used to calibrate the Transmission Control Module (TCM) for specific vehicle characteristics. Through the use of different PROM chips only one TCM is required for all applications. When the TCM operates, it checks the integrity of the RAM and ROM allocations, and if the memory allocations do not agree with the previous check, then DTC 51 will set.
Conditions for Setting the DTC
| • | Ignition ON. |
| • | TCM Checksum is incorrect. |
Action Taken When the DTC Sets
| • | TCM commands maximum line pressure. |
| • | TCM commands 2nd gear. |
| • | TCM inhibits TCC engagement. |
| • | TCM freezes shift adapts from being updated. |
| • | The TCM illuminates the Malfunction Indicator Lamp (MIL). |
| • | DTC 51 will be stored in TCM memory. |
Conditions For Clearing The DTC
History DTC(s) can be cleared by using a scan tool.
Diagnostic Aids
| • | Ensure that the PROM pins are fully seated in the socket. |
| • | If you have replaced the PROM and DTC 51 reappears, then the TCM must be replaced. Refer to TCM/Prom Replacement. |
Step | Action | Value(s) | Yes | No |
|---|---|---|---|---|
1 | Was the Powertrain On-Board Diagnostic (OBD) System Check performed? | -- | ||
2 |
Does DTC 51 set? | -- | Go to Diagnostic Aids | |
3 | Replace the PROM. Refer to TCM/PROM Replacement. Is the replacement complete? | -- | Go to Diagnostic Aids | |
4 | In order to verify your repair, perform the following procedure:
Does DTC 51 set? | -- | Refer to Diagnostic Aids | System OK |
