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.
High severity. Can I keep driving?If you smell gas, do not keep driving or start the engine: move away and call for assistance. With no smell, drive moderately to an authorized shop.
Symptoms
- Check engine light
- Cylinder C not sealed when the engine is off
Most 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
What to check, in order
Start with the simplest. You can tick off each step.
Good to know
- Repair difficulty: hard
- It affects emissions.
What each character of P2A29 means
- P: Powertrain: engine and transmission
- 2: Generic code: same on every make
- A: Hybrid or air and fuel
- 29: Specific fault in that system
Frequently asked questions
Can I keep driving with code P2A29?
If you smell gas, do not keep driving or start the engine: move away and call for assistance. With no smell, drive moderately to an authorized shop.
What causes code P2A29?
The most common causes are: 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.
Related codes
- P2A26Alternative Fuel Tank Shutoff Valve C Control Circuit/Open
- P2A27Alternative Fuel Tank Shutoff Valve C Control Circuit Performance/Stuck Off
- P2A28Alternative Fuel Tank Shutoff Valve C Control Circuit Low
- P2A25Alternative Fuel Tank Shutoff Valve B Control Circuit High
- P2A2DAlternative Fuel Tank Shutoff Valve D Control Circuit High
Sources
- transecoenergy.com: DTC List
- performanceparts.ford.com: 2014 BOSS 302S OBDII Codes
- static.nhtsa.gov: MC 10114282 9999
- law.cornell.edu: 13 CCR 1968.2
Values and procedures vary by manufacturer. If it affects brakes, steering, fuel or high voltage, see a professional. Updated: 2026-11-04. How we build these pages.