P0618
Alternative Fuel Control Module KAM Error.
- Generic
- Powertrain
- Generic code
- Low severity
How this code is built
- P
- SystemPowertrain
- 0
- Defined bySAE, the same on every car
- 6
- AreaComputer and output circuits
- 18
- FaultThe specific fault in that area
What it means
P0618 is a generic powertrain code meaning the alternative fuel control module has detected an error in its Keep Alive Memory (KAM). KAM stores learned values such as fuel trims and adaptations, and it relies on a constant battery supply. The module sets the code when the stored data fails an integrity check or has been lost or corrupted. It applies to vehicles with a separate control module for alternative fuels such as LPG, CNG or bi-fuel systems.
Symptoms
- Malfunction indicator lamp on
- Rough idle or hesitation, especially after the battery has been disconnected
- Poor or erratic running on the alternative fuel
- Car switching back to petrol or diesel, or refusing to switch to alternative fuel
- Hard starting on alternative fuel
- Learned adaptations seem to reset repeatedly
Possible causes
- Interrupted or unstable power supply to the alternative fuel module, such as a recently disconnected, flat or weak batterylikely
- Poor battery feed, ignition feed or earth connection to the module (loose, corroded or damaged terminals and wiring)likely
- Low or failing battery causing voltage drops during startingpossible
- Outdated or corrupted software or calibration in the alternative fuel modulepossible
- Internal fault in the alternative fuel control module memorypossible
- Water ingress or corrosion in the module connector or housingrare
- Poorly fitted aftermarket conversion wiring or a faulty installationrare
How to diagnose
- Read all stored codes and freeze frame data, noting any other module or power supply codes and whether the code is current or history
- Ask whether the battery has recently been disconnected, replaced or jump-started, and clear the code to see if it returns after a few drive cycles
- Test battery condition and charging system output, including voltage under cranking
- Inspect the alternative fuel module wiring, connectors, fuses and relays for damage, corrosion, water or looseness
- Check the module's battery feed, ignition feed and earth for voltage drop under load
- Check the module connector pins for spread or fretting and the wiring for signs of poor conversion work
- Check for available software or calibration updates for the module, and whether the manufacturer or conversion supplier has published a related bulletin
- If power, earth and wiring are all good and the code returns, suspect the module and confirm against model-specific procedures
How to fix
- Recharge or replace a weak battery and repair any charging system fault
- Clean, tighten or repair the module's power and earth connections and replace damaged fuses or relays
- Repair damaged, corroded or water-affected wiring and connectors
- Update or reflash the module's software or calibration where an outdated or faulty version is a known cause
- Allow the system to relearn by completing the drive cycles specified for the vehicle after clearing the code
- Replace the alternative fuel control module if confirmed faulty, and have it programmed as the manufacturer or conversion supplier requires
Can I keep driving?
The car can usually be driven, often on petrol or diesel, while you book it in. If it runs badly on the alternative fuel, stick to the main fuel until it has been checked.
Guide written by AI from the code's definition. Confirm with a diagnosis before replacing parts.