GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Cadillac 🢒 1999 🢒 Eldorado 🢒 Body and Accessories 🢒 Seats 🢒 DTC B1656 EEPROM Write Error

Circuit Description

The memory seat module (MSM) performs internal tests on the EEPROM each time that the MSM performs a write function to a memory address in the EEPROM. The MSM reads back the data that has been written and compares it to the data. If the data does not match after 3 consecutive write and verify attempts, the MSM will indicate that a write malfunction is current.

Conditions for Setting the DTC

    • The data read back after a write does not match the data being written 3 consecutive times.
    • The MSM detects an internal write malfunction.
    • The condition must occur when data is being written.

Action Taken When the DTC Sets

    • Stores a DTC B1656 in the MSM memory.
    • No driver warning message will be displayed for this DTC.
    • The MSM will store the value being written in another memory address in the EEPROM.

Conditions for Clearing the DTC

    • This DTC requires a successful write in order to change from current to history.
    • The MSM no longer detects an internal write malfunction.
    • A history DTC will clear after 50 consecutive ignition cycles if the condition for the malfunction is no longer present.
    • Use the On-Boards clearing DTCs feature.
    • Use a scan tool.

Diagnostic Aids

Since the EEPROM cannot be removed from the MSM and DTC B1656 is an internal MSM malfunction, the MSM may be replaced. Refer to diagnostic table.

Test Description

The numbers below refer to the step numbers on the diagnostic table:

  1. Perform the entire Power Seat Systems Diagnostic System Check before continuing with the diagnosis of this DTC.

    2.

  2. Clear all DTCs and cycle ignition to check that the DTC did not falsely set.

    3.

  3. Clear all DTCs after the repair procedure is complete.

Step

Action

Value(s)

Yes

No

1

Was the entire Power Seat Systems Diagnostic System Check performed?

--

Go to Step 2

Go to Diagnostic System Check - Power Seat Systems

2

  1. Turn the ignition switch to the ON position.
  2. Clear any DTCs. Refer to Diagnostic Trouble Code (DTC) Clearing .
  3. Turn the ignition switch to the OFF position.
  4. Turn the ignition switch to the ON position.

Is the DTC still present?

--

Go to Step 3

Go to Diagnostic System Check - Power Seat Systems

3

Replace the Memory Seat Module (MSM). Refer to Memory Seat Control Module Replacement .

Is the MSM replacement complete?

--

Go to Step 4

--

4

  1. Turn the ignition switch to the OFF position.
  2. Reconnect or install any connectors or components that were disconnected or removed.
  3. Turn the ignition switch to the ON position.
  4. Clear any DTCs. Refer to Diagnostic Trouble Code (DTC) Clearing .

Are all DTCs cleared?

--

Go to Diagnostic System Check - Power Seat Systems

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