Circuit Description
The powertrain control module (PCM) uses an electrically erasable programmable read only memory (EEPROM) to house the program information and the calibrations required for the engine, the transmission, and the powertrain diagnostics operation. The PCM uses a value called a checksum for error detection of the software. The checksum is a value that is equal to all the numbers in the software added together. The PCM adds all the values in the software. If that value does not equal the checksum value, a checksum error is indicated.
Conditions For Setting the DTC
The PCM detects more than 3 incorrect checksums.
Action Taken When the DTC Sets
| • | The malfunction indicator lamp (MIL) illuminates. |
| • | The PCM attempts to record the operating conditions at the time this failure is detected. However, since this is an internal PCM failure, this information may or may not be reliable. The Freeze Frame and Failure Records buffers store this information. |
| • | A history DTC is stored. |
Conditions for Clearing the MIL/DTC
| • | The MIL will turn off after 3 consecutive ignition cycles in which the diagnostic runs without a fault. |
| • | A history DTC will clear after 40 consecutive warm up cycles without a fault. |
| • | Use a scan tool to clear the DTCs. |
Test Description
The numbers below refers to the step numbers on the diagnostic table.
Step | Action | Values | Yes | No |
|---|---|---|---|---|
1 | Did you perform the Powertrain On-Board Diagnostic (OBD) System Check? | -- | ||
|
Important:: The replacement PCM must be programmed.
Did you complete the replacement? | -- | -- | ||
3 |
Does the scan tool display any DTCs? | -- | System OK |
