Powertrain, generic (extended)

P26EB Alternative Fuel Control Module System Voltage

Check engine lightOn
EmissionsRelevant
Drive cycleNot required
Limp modeNo

On bi-fuel engines a separate alternative fuel control module often runs the gas side. In Ford's bi-fuel CNG documentation of 2002 it contains drivers for both injector sets, switches the fuel relays, picks the active fuel from the selector switch and shuts the tank valve when gas pressure falls below 517 kPa. In Roush CleanTech's propane systems for Ford trucks a smart relay module takes on that role and talks to the PCM over CAN. P26EB says the supply voltage measured by or at this module is outside its permitted window, from a weak feed, a bad ground or a charging fault. No manufacturer documents P26EB publicly. CARB requires an approved monitoring plan for alternate-fuel vehicles. The vehicle will usually refuse or drop gas mode and continue on gasoline.

Likely causes

Loose, corroded or undersized power or ground connection at the gas control module
Faulty fuse, relay or feed circuit of the gas system
Weak battery or alternator voltage outside the normal range
Internal fault in the alternative fuel control module

Symptoms

  • Gas mode not available or vehicle switches back to gasoline
  • Fuel mode indicator flashes or shows a fault
  • Warning light on

Repair estimate

DifficultyMediumWorkshop job
Parts and labour€50–700
Time0.5–3 h

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

Parts involved

alt fuel control modulecharging system

Related codes

P0618P0562P0563P25BEP26E2

References: static.nhtsa.gov, roushcleantech.com, law.cornell.edu.