GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Cadillac 🢒 2005 🢒 DeVille 🢒 DTC 🢒 DTC P0601, P0602, P0603, P0604, P0605, P0606, P0607, P1600, P1621, P1627, P1680, P1681, P1683, or P2610

Description

This diagnostic applies to internal microprocessor integrity conditions within the powertrain control module (PCM). This diagnostic also addresses if the PCM is not programmed.

DTC Descriptors

This diagnostic procedure supports the following DTCs:

    • DTC P0601 Control Module Read Only Memory (ROM)
    • DTC P0602 Control Module Not Programmed
    • DTC P0603 Control Module Long Term Memory Reset
    • DTC P0604 Control Module Random Access Memory (RAM)
    • DTC P1621 Control Long Term Memory Performance
    • DTC P2610 Control Module Ignition Off Timer Performance

Conditions for Running the DTC
    • DTC P0601, P0602, P0603, P0604, and P1621 run continuously.
    • DTC P2610
       - The intake air temperature (IAT) is between -40 and +125°C (-40 and +257°F).
       - This DTC runs continuous in a 100 ms loop.
       - DTC P2610 runs continuously once the above conditions are met.

Conditions for Setting the DTC

DTC P0601

    • The PCM detects the computed read only memory (ROM) checksum is not equal to the expected checksum .
    • DTC P0601 will set within 1 second.

DTC P0602

    • The PCM detects that programming is incomplete .
    • DTC P0602 will set within 1 second.

DTC P0603

    • The PCM detects when an erroneous change occurs to the contents of the long term memory.
    • DTC P0603 will set immediately.

DTC P0604

    • The PCM detects that a bad random access memory (RAM) location has been found .
    • DTC P0604 will set within 1 second.

DTC P1621

    • The PCM detects that all blocks of nonvolatile memory storage are bad except for the one currently being used.
    • DTC P1621 will set instantaneously on key up.

DTC P2610

    • This DTC determines if the ignition off timer has failed.
    • DTC P2610 will set within 15 seconds.

Actions Taken When the DTC Sets

DTCs P0601, P0602, and P0604

    • The control module illuminates the malfunction indicator lamp (MIL) when the diagnostic runs and fails.
    • The control module records the operating conditions at the time the diagnostic fails. The control module stores this information in the Freeze Frame/Failure Records.

DTCs P1621 and P2610

    • The control module illuminates the MIL on the second consecutive ignition cycle that the diagnostic runs and fails.
    • The control module records the operating conditions at the time the diagnostic fails. The first time the diagnostic fails, the control module stores this information in the Failure Records. If the diagnostic reports a failure on the second consecutive ignition cycle, the control module records the operating conditions at the time of the failure. The control module writes the operating conditions to the Freeze Frame and updates the Failure Records.

DTC P0603

    • The control module stores the DTC information into memory when the diagnostic runs and fails.
    • The MIL will not illuminate.
    • The control module records the operating conditions at the time the diagnostic fails. The control module stores this information in the Failure Records.
    • The driver information center (DIC), if equipped, may display a message.

Conditions for Clearing the MIL/DTC

DTCs P0601, P0602, P0604, P1621, and P2610

    • The control module turns OFF the MIL after 3 consecutive ignition cycles that the diagnostic runs and does not fail.
    • A current DTC, Last Test Failed, clears when the diagnostic runs and passes.
    • A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic.
    • Clear the MIL and the DTC with a scan tool.

DTC P0603

    • A current DTC, Last Test Failed, clears when the diagnostic runs and passes.
    • A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other non-emission related diagnostic.
    • Clear the DTC with a scan tool.

Test Description

The number below refers to the step number on the diagnostic table.

  1. A DTC P0602 indicates the PCM is not programmed.

Step

Action

Yes

No

1

Did you perform the Diagnostic System Check - Vehicle?

Go to Step 2

Go to Diagnostic System Check - Vehicle in Vehicle DTC Information

2

Is DTC P0602 set?

Go to Step 3

Go to Step 5

3

Program the powertrain control module (PCM). Refer to Service Programming System (SPS) in Programming and Setup.

Does DTC P0602 reset?

Go to Step 4

Go to Step 6

4
  1. Ensure that all tool connections are secure.
  2. Ensure that the programming equipment is operating correctly.
  3. Ensure that the correct software/calibration package is used.
  4. Attempt to program the PCM. Refer to Service Programming System (SPS) in Programming and Setup.

Does DTC P0602 reset?

Go to Step 5

Go to Step 6

5

Replace the PCM. Refer to Control Module References in Computer/Integrating Systems for replacement, setup, and programming.

Did you complete the replacement?

Go to Step 6

--

6
  1. Clear the DTCs with a scan tool.
  2. Turn OFF the ignition for 30 seconds.
  3. Start the engine.

Did the DTC fail this ignition?

Go to Step 2

Go to Step 7

7

Observe the Capture Info with a scan tool.

Are there any DTCs that have not been diagnosed?

Go to Diagnostic Trouble Code (DTC) List - Vehicle in Vehicle DTC Information

System OK