Powertrain, generic (extended)

P2A34 AFCM Power Relay Control Circuit High

Check engine lightOn
EmissionsRelevant
Drive cycleNot required
Limp modePossible

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.

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

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

Repair estimate

DifficultyMediumDIY possible
Parts and labour€20–400
Time0.5–2.5 h

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

Parts involved

afcm power relayafcmwiring harness

Related codes

P2A32P2A33P2A37P0687U0108

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