Circuit Description
The module calibrations are stored in the EEPROM. When the ignition is first turned ON, the module performs internal tests on the EEPROM in order to determine the integrity of its non-volatile memory. The module compares its previously stored checksum with the checksum calculated when the ignition is first turned ON. If the 2 checksums do not match, the module will set B1558 as current.
Conditions for Setting the DTC
| • | The stored checksum does not match the calculated checksum. |
| • | The condition must occur when the ignition is first turned ON. |
Action Taken When the DTC Sets
| • | A DTC B1558 is stored in the BCM memory. |
| • | The BCM uses default values for any memory address in the EEPROM that is corrupt. |
Conditions for Clearing the DTC
| • | A current DTC clears when the malfunction is no longer present. |
| • | A history DTC clears when the module ignition cycle counter reaches the reset threshold, without a repeat of the malfunction. |
Diagnostic Aids
Since the EEPROM cannot be removed from the module and DTC B1558 is an internal module malfunction, the module may need to be replaced.
Diagnostic Aids
| • | This DTC may be stored as a History DTC with out affecting the operation of the module. If stored only as a History DTC and not retrieved as a current DTC, do not replace the module. |
| • | If this DTC is retrieved as a Current DTC, replace the module. |
Step | Action | Yes | No |
|---|---|---|---|
1 | Did you perform the Diagnostic System Check for the system exhibiting the symptom? | Go to Step 2 | Go to Control Module References for the applicable Diagnostic System Check |
2 |
Is the DTC retrieved as a current DTC? | Go to Step 3 | Go to Diagnostic Aids |
3 |
Important: Perform the programming or setup procedure for the module if required. Replace the control module setting the DTC as current. Refer to Control Module References . Did you complete the replacement? | Go to Step 4 | -- |
4 |
Does the DTC reset? | Go to Step 2 | System OK |
