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P codepowertrainMedium severity

P0618Alternative Fuel Control Module KAM Error

The alternative fuel (CNG/LPG) control module has detected a failure in its keep-alive memory (KAM), so stored adaptive data and settings are being lost or corrupted.

Definition

On vehicles equipped with an alternative fuel system (compressed natural gas or propane), the alternative fuel control module continuously verifies the integrity of its keep-alive memory, which stores learned fuel trims, configuration data, and diagnostic information between key cycles. P0618 sets when a checksum test of that memory fails or the module finds the data unreadable after power-up. The MIL typically illuminates, the system may default to gasoline-only operation or fixed base fuel values, and drivability on the alternative fuel can suffer until the fault is repaired. Because KAM depends on constant battery power, interrupted power feeds are a common trigger.

Common causes

  • Interrupted keep-alive power feed to the alternative fuel module (blown fuse, corroded connector, loose battery terminal)
  • Recent battery disconnect or deep discharge combined with a marginal module memory circuit
  • Internal failure of the alternative fuel control module's memory circuitry
  • Corrupted or failed software update/reflash of the module
  • Water intrusion or corrosion at the module connector causing intermittent power/ground loss
  • Voltage spikes from jump-starting or charging system faults corrupting stored memory

Common misdiagnoses

  • Replacing the alternative fuel injectors or regulator when the fault is module memory power
  • Replacing the vehicle battery when the module's keep-alive fuse or wiring is the problem
  • Replacing the main ECM/PCM instead of the separate alternative fuel control module
  • Condemning the module itself when a corroded ground or B+ feed is causing the memory loss

Troubleshooting steps

  1. 1.Verify battery and charging system health

    Confirm resting battery voltage above 12.4 V and charging voltage of roughly 13.5-14.8 V, since low or spiking system voltage can corrupt keep-alive memory.

  2. 2.Check the module's keep-alive power circuit

    With the key off, back-probe the constant battery feed at the alternative fuel module and confirm battery voltage with no more than 0.1-0.2 V drop; inspect the fuse and connector for corrosion.

  3. 3.Test the module grounds

    Perform a voltage-drop test on each module ground with the circuit loaded; more than 0.1 V drop indicates a poor ground that must be cleaned and re-secured.

  4. 4.Clear the code and retest

    Clear KAM, complete a full drive cycle including several key-off soak periods, and rescan; if P0618 returns with good power and ground, the module memory is failing.

  5. 5.Update or reflash the module

    Check for manufacturer software updates addressing memory errors and reflash the alternative fuel module with the OEM tool before condemning hardware.

  6. 6.Replace and configure the module if the fault persists

    Install a replacement alternative fuel control module and complete any required programming/relearn procedures per the service information.

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