Powertrain, generic (extended)

P2A29 Alternative Fuel Tank Shutoff Valve C Control Circuit High

Check engine lightOn
EmissionsRelevant
Drive cycleNot required
Limp modeNo

P2A29 sets when the drive circuit of shutoff valve C sits at a high level, as with a wire touching battery voltage or a driver stage inside the module that will not switch off. TransEco's table for its AFCM v1.4 gives a short to power as the cause, with the MIL on and gas operation maintained. Ford names P2A29 in its Boss 302S code list. GM's bi-fuel Impala powers the cut-off solenoid on its tank only while the engine cranks or runs; a valve that remains live afterwards defeats the purpose of the lock, which is to hold gas in the cylinder when the vehicle stands or the fuel supply has been cut. Wiring mistakes after a conversion deserve a look. P2A28 is the low-side code for valve C.

Likely causes

Valve C control wire in contact with battery voltage
Driver stage for valve C will not switch off
Valve C wired to a permanent feed after a conversion

Symptoms

  • Check engine light
  • Cylinder C not sealed when the engine is off

Repair estimate

DifficultyHardWorkshop job
Parts and labour€80–1,200
Time0.5–3 h

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

Parts involved

alt fuel tank shutoff valve cwiring harnessafcm

Related codes

P2A26P2A27P2A28P2A25P2A2D

References: http:, performanceparts.ford.com, static.nhtsa.gov, law.cornell.edu.