DTC P0604 Control Module Random Access Memory (RAM). GMC Truck GMC C-Series Medium Duty Truck B7 1999

For 1990-2009 cars only

Makes 🢒 GMC_Truck 🢒 1999 🢒 GMC C-Series Medium Duty Truck B7 🢒 DTC 🢒 DTC P0604 Control Module Random Access Memory (RAM)

Circuit Description

The PCM contains a memory area where it stores certain data it does not need to save when the ignition is turned OFF. This area is called the volatile section of memory. The volatile section of memory is cleared and then tested when the ignition is first turn ON. This diagnostic test monitors the PCM volatile section of memory to make sure it is stored correctly. If the information is not stored correctly,this DTC will set.

Condition for Setting the DTC

If the data from the memory location does not match the test data which was just saved to memory, DTC P0604 will set.

Action Taken When the DTC Sets

•	The PCM illuminates the Malfunction Indicator Lamp (MIL) when the diagnostic runs and fails.

•	The PCM records the operating conditions at the time the diagnostic fails. The PCM stores this information in the Freeze Frame and/or the Failure Records.

Conditions for Clearing the MIL/DTC

•	The PCM turns the MIL OFF after three consecutive drive trips that the diagnostic runs and does not fail.

•	A last test failed (current DTC) clears when the diagnostic runs and does not fail.

•	A History DTC clears after forty consecutive warm-up cycles, if this or any other emission related diagnostic does not report any failures.

•	The PCM battery voltage is interrupted.

•	Use a scan tool in order to clear the MIL/DTC.

Test Description

The number below refer to the step numbers on the diagnostic table.

Replace the PCM even if this DTC exists only in history.

Step	Action	Value(s)	Yes	No
1	Important: Before clearing any DTCs, use the scan tool Capture Info to save freeze frame and failure records for reference, as the Scan tool loses data when using the Clear Info function. Was the Powertrain On-Board Diagnostic (OBD) System Check performed?	--	Go to Step 2	Go to Powertrain On Board Diagnostic (OBD) System Check
2	Important: The new PCM must be programmed. Refer to Powertrain Control Module Replacement . Replace the PCM. Is the action complete?	--	Go to Step 3	--
3	Using the Scan tool, clear the DTCs. Start engine and idle at normal operating temperature. Select DTC, Specific, then enter the DTC number which was set. Operate the vehicle, with 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 4	Go to Step 2
4	Does the Scan tool display any additional undiagnosed DTCs?	--	Go to the Applicable DTC Table	System OK