What does it mean?
OBD II fault code P0618 is a generic code that is defined as “Alternative fuel control module -KAM error”, and is set when the PCM (Powertrain Control Module) detects a malfunction in, or failure of, the KAM ( K eep A live M emory) of the alternative fuel control module. Note that- “Keep Alive Memory” refers to memory circuits/modules in the PCM that remain powered-up when the ignition is switched “OFF”, and the battery is not disconnected.
Essentially, “Keep Alive Memory” (as it relates to this code) refers to the ever-changing operating parameters the PCM has “learned” during vehicle operation, and does NOT represent the hard-programmed operating parameters that are the same for all applications that use a specific programming.
Thus, the values stored in the Alternative Fuel Control Module Keep Alive Memory are unique to each application, since no two vehicles are driven in exactly the same way “Alternative”, or sometimes “Alternate” fuel control module refers to the control module that controls/regulates the flow of alternative fuels on vehicles that use more than one type of fuel In a fully functional system, the alternative fuel control module is just one of dozens of control modules that are all interconnected via an exceedingly complex web of harnesses that collectively, form the CAN (Controller Area Network) bus system.
During normal vehicle operation, information about a given aspect of the current operating conditions is distributed to all control modules that are involved with regulating/monitoring that particular aspect or function via the CAN bus system. In practice (on an application that uses more than one type of fuel), the PCM is continually supplied with input data from a variety of sensors such as engine temperature, engine speed, throttle position and others.
When the PCM determines that all required conditions have been met, it will switch over to the alternative fuel supply, at which time the Alternative Fuel Control Module will assume control of the application’s fuelling requirements, using the learned data values/operating parameters stored in the Alternative Fuel Control Module’s Keep Alive Memory.
However, should the PCM detect that the Keep Alive Memory relating to the Alternative Fuel control Module has failed, or is damaged in any way it will set code P0618, and depending on the application, may also illuminate a warning light. Note however, that on some applications, up to eight failure cycles need to occur before the PCM will illuminate a warning light. In these cases, code P0618 will be stored as a “pending code”, until the required number of failure cycles have occurred.