With P2A34 the coil control line of the gas module power relay stays at high voltage even when the driver tries to pull it to ground. Either the wire has contact with a battery-fed circuit, or the coil draws so much current that the driver shuts itself off for protection. In both cases the relay does not close. The consequence is the opposite of P2A33: the alternative fuel module receives no switched supply, so gas operation is impossible, and a bi-fuel car falls back to petrol from the start. Public documents for P2A34 are lacking; GM Europe treats the engine version P0687 on the 2010 Saab V6 with the same comparison of commanded against measured state. Ford's 2003 bi-fuel CNG design shows that the AFCM is a separate unit with its own power and relay outputs.
Medium severity. Can I keep driving?If the car is running normally, drive in moderation to a repair shop. If it loses power or another warning appears, do not continue.
Symptoms
- Check engine light, depending on calibration
- Gas operation unavailable, bi-fuel vehicle runs on petrol only
- Dedicated gas engine: cranks but does not start
Most likely causes
- Control wire shorted to a battery-fed circuit
- Relay coil with too low resistance overloading the driver
- Wrong relay type fitted after a repair
What to check, in order
Start with the simplest. You can tick off each step.
Good to know
- Repair difficulty: medium
- It can trigger limp mode.
- It affects emissions.
What each character of P2A34 means
- P: Powertrain: engine and transmission
- 2: Generic code: same on every make
- A: Hybrid or air and fuel
- 34: Specific fault in that system
Frequently asked questions
Can I keep driving with code P2A34?
If the car is running normally, drive in moderation to a repair shop. If it loses power or another warning appears, do not continue.
What causes code P2A34?
The most common causes are: control wire shorted to a battery-fed circuit; relay coil with too low resistance overloading the driver; wrong relay type fitted after a repair.
Related codes
- P2A32AFCM Power Relay Control Circuit/Open
- P2A33AFCM Power Relay Control Circuit Low
- P2A37AFCM Power Relay Sense Circuit High
- P0687ECM/PCM Power Relay Control Circuit High
- U0108Lost Communication With Alternative Fuel Control Module
Sources
- law.cornell.edu: 13 CCR 1968.2
- saabwisonline.com: dtc p0685 p0686 p0687 p0689 or p0690
- static.nhtsa.gov: INRD PE08063 33504P
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.