Error Code P0618 is defined as Alternative Fuel Control Module KAM Error. This means there’s an error detected in the alternative fuel control module, usually caused by a malfunction or electrical problems within the CAN.
This code is a generic trouble code, meaning it applies to all vehicles equipped with the OBD-II system, especially those made since 1996 up to present. This includes vehicles from, but not limited to, Ford, Nissan, Volkswagen, etc. Specifications on the definition, troubleshooting, and repairs, of course, vary from one make and model to another.
However, this code is exclusive to vehicles that use alternative fuels like natural gas and electricity for propulsion.
When Error Code P0618 is stored, this means the PCM (powertrain control module, also known as ECM or engine control module in other vehicle makes), has seen a malfunction in the AFCM (Alternative Fuel Control Module). This problem has occurred in the KAM (Keep-Alive Memory) part of the AFCM/PCM.
In some cases, the AFCM and PCM may be built separately. However, they’re commonly integrated into a single module, increasing the efficiency of the controller, and saving automakers space and money.
The KAM works by allowing the PCM and other controllers to keep data even when the ignition is turned off, or the battery is briefly interrupted.
Every time the ignition is turned on and the PCM is energized, multiple controllers perform self-tests. Aside from running internal controller self-tests, the CAN (controller area network) is used to compare signals from the individual module, ensuring various controllers are working and interacting correctly.
If a problem is detected when monitoring AFCM/PCM KAM capacity, then Error Code P0618 will be stored, and simultaneously activating the Check Engine light. Depending on the severity of the problem, it may take multiple drive cycles for the Check Engine light to light up.
This code causes vehicle drivability issues, such as:
- Stalling while idling
- Slow acceleration
- Harsh shifting
- Increase in fuel consumption
- Delayed engine cranking (especially when cold)
Other stored code may be present
Common causes for this code include:
- Malfunctioning AFCM
- Shorted or open wires in CAN
- Corroded, damaged, or loose connectors in CAN bus harness
- Loose or damaged ground strap or ground wire in the control module
- Insufficient control module ground
- Defective CAN bus
How to Check
This code is one of the many tricky codes to diagnose and fix, even with professional technicians. Also, reprogramming issue must also be considered. Without the right reprogramming equipment, it will be impossible to replace a defective controller and complete the repair.
If there are other AFCM/PCM codes present, then they must be addressed first before diagnosing P0168
Start the diagnosis by connecting the OBD-II scanner, read the codes stored in the PCM and see if any related codes may be the root of the problem. After reading all saved codes, do a visual inspection of all circuits and wirings. Check the connectors and wirings using an ohmmeter to ensure there are no open or short circuits.
Then, check the PCM, CAN bus, and other relevant components.
When trying to diagnose this code, refer to your information source or TSB (technical service bulletin); looks for signs and symptoms parallel to the stored code. Search for the year, make, model, and engine of your vehicle. If you can find the right TSB, then you may get the best diagnostic information about your problem.
Use vehicle information source to obtain component locations, connector face views, connector pin-out charts, wiring diagram, and diagnostic flow chart related to your vehicle’s error code.
Then, use the DVOM to the test controller power supply fuses and relays. Next, test and replace any blown fuses as necessary. Fuses must be tested with circuit loaded.
If all fuses and relays are running well, check whether the controller related wiring and harness are in order. You may also want to check chassis and engine ground junctions. Again, use your vehicle information source to obtain ground locations as related circuits. Test ground integrity using the DVOM.
Then, check the system controllers for any signs of water, heat, or collision damage. Any controller that is damaged, especially by water, is considered defective and must be replaced.
If controller power and ground circuits are intact, then there’s a good chance the controller is defective, or there’s a programming error in the controller. Thus, controller replacement requires reprogramming. In some cases, you may want to get aftermarket reprogrammed controllers. Some vehicles and controllers require on-board reprogramming that may be done only through the dealership or a qualified shop.
How to Fix
Depending on your diagnosis, common repairs for this code include:
- Replacement of the AFCM
- Replacement of damaged wires, connectors, and fuses in the module
- Replacement of ground straps and ground wires
- Replacement of wires and connectors in the CAN bus
- Replacement of the CAN bus (rare)
Though this code may not keep your vehicle from being driven, it comes with various drivability issues that could pose safety concerns and could lead further cause serious damage to the engine. Thus, it must be addressed as soon as possible.