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U0309 Software Incompatibility With Alternative Fuel Control Module

Check engine lightOn
EmissionsRelevant
Drive cycleNot required
Limp modePossible

An alternative fuel control module runs the gaseous fuel side of a bi-fuel or dedicated LPG or CNG engine and works alongside the gasoline or diesel controller. CARB counts such engines as alternate-fueled vehicles that fall under OBD II. U0309 is set when the partners find the module's software or calibration does not match theirs, for example after a conversion system or one of the controllers was updated on its own. Ford's 2014 code interpretation lists U0309 with the MIL marker. Roush CleanTech's propane systems for Ford E- and F-Series trucks show the arrangement: a smart relay module of the propane side talks to the Ford PCM and keeps its own fault list, including an internal software incompatibility code. U0108 means lost contact, U0409 invalid data. Expect a MIL and a fallback to the base fuel or rough running on gas.

Likely causes

Gas system module software not released for the current engine controller calibration
PCM/ECM reflashed by a dealer without updating the gas system module
Gas system module replaced with a unit of another variant

Symptoms

  • Engine stays on or switches back to gasoline/diesel
  • MIL and gas system warning on
  • Rough running or hesitation in gas mode

Repair estimate

DifficultyShop_onlyWorkshop job
Parts and labour€100–800
Time0.5–3 h

Typical range across vehicles; the real cost depends on what the testing finds.

Parts involved

alternative fuel modulecontrol module software

Related codes

U0108U0409U0300U0301

References: performanceparts.ford.com, roushcleantech.com, law.cornell.edu.