For 1990-2009 cars only
Circuit Description
The module performs internal tests on the EPROM. Each time the module performs a write function to the EPROM, the module reads back the data that has been written and makes a comparison. If the data does not match after 3 consecutive write and verify attempts, the module will set B1556 as current.
Conditions for Setting the DTC
| • | The data read back after a write does not match the data being written after 3 consecutive attempts. |
| • | The condition must occur when data is being written. |
Action Taken When the DTC Sets
| • | A DTC B1556 is stored in the PZM memory. |
| • | No driver warning message is be displayed for this DTC. |
| • | The PZM stores the value being written in another memory address in the EPROM. |
Conditions for Clearing the DTC
| • | This DTC requires a successful write in order to change from current to history. |
| • | The module no longer detects an internal write malfunction. |
| • | A history DTC clears after 50 consecutive ignition cycles if the condition for the malfunction is no longer present. |
Diagnostic Aids
Since the EPROM cannot be removed from the module and DTC B1656 is an internal module malfunction, the module may need to be replaced.
Step | Action | Value(s) | Yes | No |
|---|---|---|---|---|
1 | Was the Body Control Module Diagnostic System Check performed? | -- | Go to Step 2 | |
2 |
Is the DTC still present? | -- | ||
3 | Replace the PZM. Refer to Body Control Module Replacement . Is the repair complete? | -- | -- | |
4 |
Is the repair complete? | -- | -- |
