Circuit Description
The calibrations for the heater and A/C control are stored in EEPROM. When the ignition is first turned On, the controller performs internal tests on the EEPROM and can determine the integrity of the EEPROM's non-volitale memory. The controller compares its previously stored checksum with the checksum calculated when the ignition was first turned On. If the two checksums do not match, the controller indicates that a calibration error (checksum error) has occured.
Conditions for Setting the DTC
| • | The stored checksum does not match the calculated checksum. |
| • | The controller detects an internal memory malfunction (checksum error). |
| • | The condition is present when the ignition is first turned On. |
Action Taken When the DTC Sets
| • | Stores a DTC 51 in the controllers memory. |
| • | Disables all heater and A/C control functions. |
Conditions for Clearing the DTC
| • | The condition for the fault is no longer present. |
| • | The use of a scan tool. |
| • | A history DTC will clear after 20 consecutive ignition cycles if the condition for the fault is no longer present. |
Test Description
The number(s) below refer to the step number(s) on the diagnostic table.
Step | Action | Value(s) | Yes | No |
|---|---|---|---|---|
1 | Did you perform the HVAC Systems Diagnostic System Check? | -- | Go to Step 2 | Go to Diagnostic System Check |
Replace the heater and A/C control module. Did you complete the replacement? | -- | System OK | -- |
