What does it mean?
This generic powertrain diagnostic trouble code (DTC) generally applies to many OBD-II vehicles. This may include, but is not limited to, vehicles from Volkswagen VW, Ford, Nissan, etc.
A stored P0618 code means that the Powertrain Control Module (PCM) has detected a malfunction with the Alternative Fuel Control Module (AFCM). The issue occurred in the Keep Alive Memory (KAM) portion of the AFCM/PCM.
The P0618 code is limited to vehicles that use alternative fuels such as natural gas and electricity for propulsion.
In some cases, the AFCM and PCM may be separate from each other. Most often, they are integrated into a single module. This increases controller efficiency in addition to saving space, time, and money for car manufacturers.
KAM allows the PCM and other controllers to retain data even when the ignition is turned off or the battery is briefly disconnected.
Whenever the ignition is turned on and the PCM is powered up, several controller self-tests are performed. In addition to running internal controller self-tests, the Controller Area Network (CAN) is used to compare signals from each individual module to ensure that the various controllers interact correctly.
When monitoring the AFCM/PCM KAM capability, if a problem is detected, a P0618 code will be stored and a Malfunction Indicator Lamp (MIL) may be illuminated. Depending on the perceived severity of the malfunction, several failure cycles may be required for the MIL to light up.
Example photo of a fuel pump control module:
P0618 Fuel Pump Control Module
How severe is this DTC?
Internal control module codes should always be taken seriously. A stored P0618 code can lead to various drivability issues, as valuable controller memory may be lost.
What are some of the symptoms of the code?
Symptoms of a P0618 fault code may include:
Engine drivability problems
Engine stalling at idle
Delayed engine starting (especially when cold)
Other stored codes
What are some common causes of the code?
Causes
of this code may include:
Faulty AFCM/PCM
AFCM/PCM programming error
Open or shorted circuit or connectors in the CAN bus
AFCM/PCM power source failure
Insufficient control module ground
What are the troubleshooting steps for P0618?
Unfortunately, even the most experienced and well-equipped professional technician may find diagnosing a P0618 code quite challenging. There is also the issue of reprogramming. Without the necessary reprogramming equipment, it will be impossible to replace a faulty controller and perform a successful repair.
If AFCM/PCM power codes are present, they will need to be repaired before attempting to diagnose a P0618.
There are several preliminary tests that can be performed before declaring a controller faulty. A diagnostic scanner, a digital volt/ohmmeter (DVOM), and a reliable vehicle information source will be required.
Connect the scanner to the vehicle’s diagnostic port and retrieve all stored codes and freeze frame data. You will want to note this information, just in case the code turns out to be intermittent. After recording all relevant information, clear the codes and test the vehicle until the code resets or the PCM enters readiness mode. If the PCM enters readiness mode, the code is intermittent and will be more difficult to diagnose. The condition that caused the P0618 to be stored may even need to worsen before a diagnosis can be made. If the code resets, continue with this short list of preliminary tests.
When trying to diagnose a P0618, information can be your best tool. Search your vehicle information source for Technical Service Bulletins (TSBs) that correlate the stored code, the vehicle (year, make, model, and engine), and the symptoms presented. If you find the right TSB, it can provide diagnostic information that will greatly assist you.
Use your vehicle information source to obtain connector face views, connector pinout diagrams, component locators, wiring diagrams, and diagnostic flowcharts related to the code and the specific vehicle.
Use the DVOM to test the controller’s power fuses and relays. Replace blown fuses as needed. Fuses should be tested with the circuit loaded.
If all fuses and relays appear to be functioning as expected, a visual inspection of the wiring and harnesses related to the controller is necessary. You will also want to check the chassis and engine ground junctions. Use your vehicle information source to obtain ground locations for the related circuits. Use the DVOM to test ground integrity.
Visually inspect the system controllers for signs of water, heat, or collision damage. Any damaged controller, especially by water, should be considered faulty.
If the controller’s power and ground circuits are intact, suspect a faulty controller or a controller programming error. Replacing the controller will require reprogramming. In some cases, you can purchase controller reprogramming through aftermarket sources. Other vehicles/controllers will require onboard reprogramming that can only be performed by a dealership or another qualified source.
Unlike most other codes, P0618 is likely caused by a faulty controller or a controller programming error
Test the system ground integrity by connecting the DVOM’s negative test lead to ground and the positive test lead to battery voltage