P0618 Alternative Fuel Control Module Keep Alive Memory (KAM) Error

The P0618 – Alternative Fuel Control Module Keep Alive Memory (KAM) Error diagnostic trouble code (DTC) indicates that the Alternative Fuel Control Module (AFCM) has detected a problem with its Keep Alive Memory (KAM).

In simple terms:

The alternative-fuel control module is not correctly retaining or accessing the information that should remain stored when the ignition is switched off.

KAM is a type of memory that allows a control module to retain certain learned values, settings, adaptations, or operational information even when the vehicle is not running.

P0618 does not automatically mean that the alternative-fuel control module is defective. A low battery voltage, interrupted power supply, poor ground, wiring problem, blown fuse, connector problem, or internal module failure can cause this code.

What Is Keep Alive Memory (KAM)?

Keep Alive Memory is used by vehicle control modules to retain information when the ignition is turned off.

Depending on the vehicle, the AFCM may retain information such as:

• Learned fuel-system values

• Adaptation values

• Calibration information

• Fuel-system settings

• Operating parameters

• Diagnostic information

The exact information stored in KAM varies by manufacturer.

The module needs a continuous or appropriately maintained power supply to preserve this information.

A simplified system can be represented as:

Battery → Fuse → AFCM Keep-Alive Power → KAM

If this power supply is interrupted unexpectedly, the module may detect a KAM error and store P0618.

What Does P0618 Mean?

P0618 specifically concerns the Keep Alive Memory function of the Alternative Fuel Control Module.

The AFCM monitors its internal memory and associated power supply.

If the stored information is lost, corrupted, or cannot be accessed as expected, the module may determine that its KAM function has failed.

This can happen because of:

Low voltage → Power interruption → Memory information lost → P0618

It can also happen because of:

Internal AFCM memory failure → KAM cannot operate correctly → P0618

What Causes P0618?

Possible causes include:

• Weak battery

• Completely discharged battery

• Battery disconnected

• Poor battery terminal connection

• Blown fuse

• Open KAM power circuit

• Damaged wiring

• Corroded connector

• Poor ground

• Intermittent power supply

• Charging-system problem

• Voltage drop during engine cranking

• Water intrusion

• Internal AFCM memory failure

• AFCM software corruption

• Interrupted module programming

• Faulty alternative-fuel control module

The exact cause depends on the vehicle's electrical architecture.

Can a Weak Battery Cause P0618?

Yes.

A weak battery is one of the first things that should be checked.

If battery voltage drops excessively during starting, the AFCM may temporarily lose its required operating voltage.

For example:

Weak battery → Voltage drops during cranking → AFCM resets → KAM information becomes invalid → P0618

A battery that has recently gone completely flat is particularly relevant.

Can Disconnecting the Battery Cause P0618?

Potentially, yes.

Disconnecting the battery can erase or reset certain learned values in vehicle control modules.

A normal battery disconnect does not necessarily mean that the AFCM is defective.

However, if P0618 appears immediately after battery removal, replacement, or a major electrical repair, check the module's KAM power circuit and manufacturer-specific reset/relearn procedures.

Can a Bad Alternator Cause P0618?

Yes, indirectly.

If the alternator is not charging correctly, system voltage can become too low or unstable.

This can affect the AFCM's ability to retain or access its memory.

Check:

• Alternator output

• Battery voltage

• Charging-system wiring

• Battery terminals

• Engine grounds

If P0618 appears with generator or system-voltage codes, the charging system deserves particular attention.

Can a Blown Fuse Cause P0618?

Yes, depending on the vehicle.

The AFCM may have a dedicated battery-power or keep-alive power circuit protected by a fuse.

If that circuit loses power while the ignition is off, KAM information may not be retained correctly.

Check the relevant:

• AFCM fuse

• Battery-power fuse

• Ignition fuse

• Control-module power circuit

Do not simply replace a repeatedly blown fuse. A recurring blown fuse indicates an underlying electrical fault.

Can a Poor Ground Cause P0618?

Yes.

The AFCM needs a reliable ground connection.

A poor ground can cause:

• Module resets

• Voltage instability

• Memory errors

• Communication problems

• Intermittent operation

Inspect the AFCM ground and related chassis/engine grounds.

A voltage-drop test under load is preferable to relying only on a continuity test.

Can Wiring Cause P0618?

Yes.

A damaged KAM power wire can interrupt the module's memory supply.

Inspect wiring for:

• Broken conductors

• Corrosion

• Chafing

• Heat damage

• Loose terminals

• Water intrusion

• Previous repair work

Pay particular attention to the AFCM connector and wiring harness.

Can a Bad Connector Cause P0618?

Yes.

A loose or corroded terminal can intermittently interrupt the AFCM's power or ground.

Inspect for:

• Corrosion

• Bent pins

• Loose terminals

• Burned contacts

• Water contamination

• Damaged seals

An intermittent connection can be particularly difficult to diagnose because the vehicle may operate normally for long periods.

Can P0618 Be Caused by Low Voltage During Starting?

Yes.

This is an important diagnostic possibility.

The battery may show acceptable voltage with the engine off, but voltage can fall significantly during cranking.

If the AFCM loses stable power during this period, it may reset or detect a memory problem.

Therefore, check voltage:

Engine off → During cranking → Engine running

rather than checking only static battery voltage.

Symptoms of P0618

Possible symptoms include:

• Check Engine Light

• Alternative-fuel warning

• Fuel-mode switching problems

• Loss of alternative-fuel operation

• Difficulty starting

• Rough operation

• Reduced engine performance

• Poor fuel economy

• Repeated loss of learned values

• Intermittent fuel-system problems

• Communication faults

Some vehicles may store P0618 without obvious symptoms.

Can P0618 Prevent Alternative-Fuel Operation?

Yes, potentially.

If the AFCM cannot reliably maintain its required memory or operating parameters, the vehicle may disable or restrict alternative-fuel operation.

Depending on the system, the vehicle may:

• Switch to another available fuel

• Restrict fuel-mode selection

• Enter a protective strategy

• Reduce engine performance

• Prevent starting

The exact response depends on the vehicle manufacturer.

Can P0618 Cause a No-Start Condition?

Potentially.

The effect depends on how essential the AFCM is to engine starting.

On some alternative-fuel vehicles, the module may be directly involved in fuel selection and fuel delivery.

If its stored configuration or learned information is lost, the engine may have difficulty starting.

On a dual-fuel vehicle, the system may instead switch to another fuel source.

Is P0618 a Serious Code?

It can be.

If the vehicle is operating normally, the immediate mechanical risk may be limited.

However, an unresolved KAM power problem can cause the AFCM to repeatedly lose information or reset.

The situation becomes more serious if there are:

• Starting problems

• Fuel-mode switching problems

• Engine stalling

• Reduced power

• Multiple electrical codes

• Repeated battery discharge

Can You Drive With P0618?

If the vehicle starts and operates normally, a short trip to a repair facility may be possible.

However, driving should be limited if the vehicle:

• Stalls

• Has difficulty starting

• Loses power

• Cannot switch fuel modes

• Displays multiple electrical warnings

An intermittent power-supply problem can become a complete power failure.

How Is P0618 Diagnosed?

A systematic diagnosis is important.

1. Scan all control modules

Look for:

• P0618

• Other AFCM codes

• Voltage codes

• Generator codes

• Communication U-codes

• Fuel-system codes

2. Check battery condition

Test battery state of charge and condition.

3. Test voltage during cranking

Look for excessive voltage drop.

4. Check charging voltage

Verify alternator operation.

5. Identify the AFCM KAM power circuit

Use the correct vehicle wiring diagram.

6. Check the KAM fuse

Verify both fuse condition and power supply.

7. Check AFCM power

Make sure the module receives the correct constant battery supply.

8. Check AFCM grounds

Perform voltage-drop testing.

9. Inspect connectors

Look for corrosion, loose terminals and water intrusion.

10. Inspect wiring

Check for intermittent opens and shorts.

11. Check software and programming

Determine whether a manufacturer update or reprogramming procedure is available.

12. Test the AFCM

If all external circuits are correct, an internal module problem becomes more likely.

How Do You Test the KAM Power Supply?

The exact procedure varies by vehicle, but the basic concept is:

Identify constant battery power → Measure voltage with ignition OFF → Measure voltage with ignition ON → Monitor voltage during cranking → Check voltage under load

The important point is that KAM power may need to remain available even when the ignition is switched off.

If the power supply disappears when it should remain present, the module may lose its retained memory.

Why Is Constant Power Important?

KAM is specifically designed to retain certain information when the vehicle is switched off.

A simplified example:

Ignition OFF → Battery still supplies KAM → AFCM retains memory

If the KAM supply is interrupted:

Ignition OFF → KAM power lost → Stored information may be lost → P0618

The actual circuit design varies by vehicle, but this illustrates why constant battery power is important.

Can a Battery Terminal Problem Cause P0618?

Yes.

A loose or corroded battery terminal can intermittently disconnect power from the vehicle.

This can result in:

• Module resets

• Clock/radio resets

• Loss of learned values

• Communication codes

• KAM-related codes

Battery terminals should be clean and securely tightened.

Can a Main Ground Problem Cause P0618?

Yes.

A poor main ground can affect multiple modules simultaneously.

If P0618 occurs together with several seemingly unrelated codes, inspect:

• Battery negative connection

• Engine ground strap

• Chassis grounds

• AFCM ground

• ECM/PCM grounds

A common ground fault can create multiple control-module errors.

Can P0618 Be Caused by Software?

Yes.

A corrupted software image or calibration problem can potentially cause memory-related errors.

This is especially relevant if P0618 appeared:

• After module programming

• After a software update

• After replacing the AFCM

• After a communication interruption during programming

Manufacturer-approved reprogramming may be required.

Can Reprogramming Fix P0618?

Sometimes.

If the problem is caused by corrupted software or incorrect calibration, reprogramming the AFCM may correct it.

However, reprogramming will not repair:

• Failed memory hardware

• Damaged wiring

• Missing KAM power

• Poor grounds

• A defective module

The electrical supply should be verified before programming.

Does P0618 Mean the AFCM Is Bad?

No, not automatically.

This is one of the most important points when diagnosing this code.

Before replacing the module, verify:

Battery → Charging system → KAM fuse → Constant power → Ground → Wiring → Connectors → CAN communication → Software → AFCM

If the AFCM receives correct power and ground and continues to report a KAM error, an internal module problem becomes more likely.

What If P0618 Appears With P0619?

These two codes are closely related.

P0618 indicates an Alternative Fuel Control Module KAM error.

P0619 indicates an Alternative Fuel Control Module RAM/ROM error.

If both appear together, investigate the AFCM's:

• Power supply

• Ground

• Memory operation

• Software

• Programming

• Internal electronics

However, do not immediately replace the AFCM. Low voltage or an intermittent power supply can potentially create multiple memory-related codes.

What If P0618 Appears With P0562?

P0562 – System Voltage Low is highly relevant.

If P0618 and P0562 occur together, check:

Battery → Alternator → Battery cables → Grounds → AFCM power supply

Low system voltage may be the underlying cause.

What If P0618 Appears With Generator Codes?

Generator/alternator codes can indicate a charging-system problem.

If P0618 appears with codes such as P0620-series generator faults, check the charging system before condemning the AFCM.

A failing alternator can create unstable system voltage that affects control modules.

What If P0618 Appears With U-Codes?

Communication codes may indicate a broader electrical or network problem.

Check:

• Battery voltage

• AFCM power

• AFCM ground

• CAN-H

• CAN-L

• Connectors

• Network wiring

If several modules lose communication simultaneously, investigate the common power and network circuits first.

Can P0618 Be Fixed Without Replacing the AFCM?

Yes.

Possible repairs include:

• Replacing a blown fuse after correcting its cause

• Repairing KAM power wiring

• Repairing a damaged ground

• Cleaning or replacing corroded terminals

• Repairing battery connections

• Repairing charging-system problems

• Repairing CAN wiring

• Correcting water intrusion

• Updating AFCM software

• Reprogramming the AFCM

If the AFCM's internal memory hardware has failed, module replacement may ultimately be necessary.

Does a Replacement AFCM Need Programming?

Often, yes.

Depending on the vehicle, a replacement AFCM may require:

• Software programming

• Configuration

• Calibration

• Vehicle-specific coding

• Fuel-system configuration

• Security/immobilizer synchronization

Installing a replacement module without completing the required programming can result in additional faults.

Can P0618 Be Cleared With an OBD Scanner?

Yes.

A compatible diagnostic scanner can generally clear the stored DTC after the problem has been repaired.

However:

Clearing P0618 does not repair the KAM circuit.

If the module continues to lose its required power or detects an internal memory problem, the code will return.

The correct sequence is:

Diagnose → Repair → Clear → Test → Rescan

Common Diagnostic Mistakes

Replacing the AFCM immediately

The module may simply be losing its KAM power supply.

Ignoring the battery

A weak battery can create voltage drops that affect control modules.

Ignoring the charging system

An alternator problem can create unstable system voltage.

Checking only battery voltage with the engine off

Voltage should also be monitored during cranking and engine operation.

Ignoring grounds

A poor ground can cause intermittent module resets.

Replacing a fuse without investigating why it failed

A repeatedly blown fuse usually indicates an underlying electrical problem.

Programming a module with unstable voltage

Module programming should be performed with the correct stable power supply according to manufacturer procedures.

How Is P0618 Repaired?

The appropriate repair depends on the confirmed cause.

Possible repairs include:

• Repairing KAM power wiring

• Replacing damaged wiring

• Repairing or replacing connectors

• Repairing battery connections

• Repairing AFCM grounds

• Replacing a faulty fuse

• Repairing alternator/charging-system problems

• Repairing CAN communication wiring

• Correcting water intrusion

• Updating AFCM software

• Reprogramming the AFCM

• Replacing the AFCM when internal failure is confirmed

How Do You Clear P0618?

After completing the repair:

Scan all modules → Check battery → Test voltage during cranking → Check charging system → Check KAM fuse → Verify constant AFCM power → Check grounds → Inspect connectors → Check wiring → Check CAN communication → Check AFCM software → Reprogram if necessary → Replace module if confirmed faulty → Clear DTC → Verify fuel-system operation → Road test → Rescan

If the AFCM retains its memory correctly and P0618 does not return, the repair is likely successful.

Final Thoughts on P0618

P0618 – Alternative Fuel Control Module Keep Alive Memory (KAM) Error indicates that the alternative-fuel control module has detected a problem with its Keep Alive Memory function.

The key point is that P0618 does not automatically mean the AFCM needs to be replaced.

The first areas to investigate are:

Battery → Charging system → KAM fuse → Constant power supply → Ground → Wiring → Connectors → CAN communication → Software → AFCM

If the code appeared after a dead battery, battery replacement, jump-start, electrical repair, or module programming, those events are particularly important during diagnosis.

If the AFCM has correct and stable power and ground, the wiring and communication network are intact, and the code returns after proper reprogramming, an internal AFCM memory or hardware failure becomes much more likely.