GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 GMC_Truck 🢒 1999 🢒 GMC Suburban - 4WD 🢒 Engine 🢒 Engine Controls - 7.4L 🢒 DTC P0603 Control Module Long Term Memory Reset

Circuit Description

The control module contains a section of non-volatile memory where it stores data values it needs to save when the ignition is turned OFF. This is referred to as the keep alive memory. After the ignition is turned OFF, the control module adds the data in all of these memory locations. This value is called the checksum. The control module also performs the same function when the ignition is turned ON. If at key ON the checksums do not match, this diagnostic trouble code (DTC) will be set.

Since this diagnostic pertains to an internal VCM diagnostic check, no wiring schematic is required.

Conditions for Running the DTC

The ignition switch is in the run position.

Conditions for Setting the DTC

A difference was detected in the data stored in the keep-alive memory at power-down when compared with the data retrieved from the keep-alive memory at power-up.

Action Taken When the DTC Sets
    • The control module illuminates the malfunction indicator lamp (MIL) the first time the diagnostic runs and fails.
    • The control module will set the DTC and records the operating conditions at the time the diagnostic fails. The control module stores the failure information in the scan tools Freeze Frame/Failure Records.

Conditions for Clearing the MIL or DTC
    • The control module turns OFF the MIL after 3 consecutive drive trips when the test has run and passed.
    • A history DTC will clear if no fault conditions have been detected for 40 warm-up cycles. A warm-up cycle occurs when the coolant temperature has risen 22°C (40°F) from the startup coolant temperature and the engine coolant reaches a temperature that is more than 70°C (158°F) during the same ignition cycle.
    • Use a scan tool in order to clear the DTCs.

Diagnostic Aids

If the battery has been disconnected for any reason DTC P0603 may set. The VCM checks the memory at powerup. If the memory changes, it will reset. An intermittent loss of power or ground to the VCM will also cause a reset.

Step

Action

Value(s)

Yes

No

1

Important: Before clearing the DTCs, use the scan tool Capture Info to save the Freeze Frame and Failure Records for reference. The control module's data is deleted once the Clear Info function is used.

Did you perform the Powertrain On-Board Diagnostic (OBD) System Check?

--

Go to Step 2

Go to Powertrain On Board Diagnostic (OBD) System Check

2
  1. Clear the DTCs.
  2. Turn OFF the ignition.
  3. Turn ON the ignition leaving the engine OFF.

Did this DTC reset?

--

Go to Step 3

System OK

3
  1. Replace the VCM.
  2. Program the new VCM. Refer to VCM Replacement/Programming .
  3. Perform the Passlock Reprogramming Procedure. Refer to PASSLOCK Reprogramming Seed and Key in Theft Deterrent.
  4. Perform the CKP System Variation Learn Procedure. Refer to Crankshaft Position System Variation Learn .

Is the action complete?

--

Go to Step 4

--

4
  1. Using the scan tool, clear the DTCs.
  2. Start the engine.
  3. Allow the engine to idle until the engine reaches normal operating temperature.
  4. Select DTC and the Specific DTC function.
  5. Enter the DTC number that was set.
  6. Operate the vehicle, within the Conditions for Setting this DTC, until the scan tool indicates the diagnostic Ran.

Does the scan tool indicate the diagnostic Passed?

--

Go to Step 5

Go to Step 2

5

Does the scan tool display any additional undiagnosed DTCs?

--

Go to the applicable DTC table

System OK