Trouble code solution P0604: decoding, causes, resetting, meaning

Contents

Technical description and explained code P0604
Symptoms of vehicle malfunctions
Factors that can cause this error code
How to fix or reset OBD-2 code P0604
Diagnose and repair of problems
Checking and reprogramming
On which vehicles does this problem occur most frequently
Video

Fault code P0604 is called “Internal Control Module Random Access Memory (RAM) Error” but in different programs it may be called differently. This fault designation applies to all vehicles equipped with OBD-II.

Technical description and explained code P0604

OBD-II code P0604 is defined as “internal RAM error of the control module”. Set when a RAM error is detected in the powertrain control module (PCM).

The PCM module is programmed with important engine control information as well as other systems. It contains so much information that it would take too long to access every bit of it every time an engine control response is initiated.

RAM contains a selected, set amount of data that allows the PCM to respond faster in rapid succession. That is, RAM allows you to quickly find data that is regularly accessed, on demand.

Specific settings for engine and transmission control are programmed into RAM for each vehicle produced. Not only does it help manage engine efficiency and performance more quickly. But it also allows other on-board vehicle control modules to be recognized and interact with them.

If the PCM detects a mismatch between the RAM and other controllers, or if the RAM is not functioning properly. Then code P0604 will be stored and the Malfunction Indicator Light (MIL) may illuminate. Depending on the severity of the fault, it may take several failure cycles for the MIL to appear.

Essentially, error P0604 means there is a RAM problem in the powertrain control module (PCM).

Symptoms of vehicle malfunctions

The main signal that an error P0604 has occurred is the Malfunction Indicator Lamp (MIL) is also known as the CheckEngine Light.

It can also be warning signs such as:

The “Check engine” control lamp on the control panel will light up (the code will be recorded in the memory as a fault).
Floating revolutions, as well as attempts to stall at idle.
Multiple handling problems.
Sharp or unstable shifting of automatic transmission.
Reduced engine power.
Increased fuel consumption.
Problems with a particular system, indicating a possible loss of communication in that area.

Fault code P0604 indicates a RAM error. Depending on what the failure affects, the error may be either severe or moderate.

Factors that can cause this error code

The error code P0604 can mean that one or more of the following problems have occurred:

Powertrain Control Module (PCM) programming error.
If the engine control module has been replaced, it may need to be programmed.
Bad power supply relay of ECM / PCM.
Open or short circuit in wiring harness.
Loose or damaged connectors.
Poor grounding is a common cause.
Blown engine-ECU fuse.
CAN bus may be faulty and have a short to ground or wire breakage.
Sometimes the cause is a faulty PCM module.

How to fix or reset OBD-2 code P0604

Some suggested steps for troubleshooting and fix the error code P0604:

Read all stored data and error codes with an OBD-II scan tool. To find out when and under what circumstances error P0604 appeared.
Clear the error codes from the computer memory and test-drive the vehicle to find out if the malfunction appears again.
If the error code appears again, visually inspect the electrical wires and powertrain control module (PCM) connector.
Measure battery voltage and compare it to the manufacturer’s specification.
Check continuity of powertrain control module (PCM) power and ground circuits with multimeter.
Try reprogramming the control module.
Evaluate powertrain control module (PCM) operation following vehicle manufacturer’s procedure.
Clear the error code from the computer memory again, and test drive the vehicle to see if the problem is resolved.

Diagnose and repair of problems

To correct code P0604, the most common solution is to replace and reprogram the PCM. Although, faulty wiring should also be considered as a cause of this error.

Perform a thorough visual inspection of all points where the wiring rests on the body. These points represent ground connections. You will often find loose connections or even ground straps that hang down after unrelated repairs have been made.

If bad ground connections have been found and repaired, remove all codes and re-scan the system to see if any codes return. In some cases it may be necessary to re-integrate or even reprogram some controllers after a communication failure.

If all ground connections are secure, perform a thorough visual inspection of all wiring on the vehicle. Note that this inspection may require the removal of the dashboard, seats, carpets, and even trim panels to gain access to all wiring harnesses.

If no wiring damage is found, but the P0604 code remains despite following the steps above. One option may be to replace the entire electrical harness. However, this does not guarantee that the problem will be solved because the problem may be related to the controller.

Typical problems with controllers include faulty drivers, memory failure, or other components for any number of reasons. For this reason, replacing the entire harness is not recommended. Until exhaustive diagnostic tests have been performed on all controllers, including the PCM.

Checking and reprogramming

If the PCM has recently been replaced, there is a good chance that it has been improperly programmed or not programmed at all. In addition, you cannot use a controller from another vehicle. Unless it has been reprogrammed specifically for the vehicle in question.

Aftermarket (high performance) firmware may not be recognized by other controllers, resulting in a stored P0604.

Improperly programmed or replaced controllers may be reprogrammed by the factory scan tool. If you can’t access such a scanner, most dealerships offer PCM programming for a nominal fee.

Some aftermarket PCM manufacturers offer preprogrammed controllers for certain models. Contact your auto parts supplier and get the vehicle identification number, mileage, and other pertinent data.