Powertrain, generic (extended)

P2A37 AFCM Power Relay Sense Circuit High

Check engine lightOn
EmissionsRelevant
Drive cycleNot required
Limp modeNo

Here the read-back line of the gas module supply relay carries voltage at a moment when it should not: the relay is commanded off, yet power is still present behind its contacts. A welded contact pair is the main suspect, followed by a sense wire touching another live circuit. The practical effect is a gas control module that never shuts down, so stored values may not be saved correctly and the battery drains while parked. The 2010 Saab V6 manual from GM Europe covers the engine relay counterpart P0690 within the same feedback test as P0689. P2A37 itself appears in no public manufacturer document. Ford's 2003 bi-fuel CNG pickups illustrate that the alternative fuel module is a separate box with its own relay outputs, which explains why J2012 gives it a relay code set of its own.

Likely causes

Relay contacts welded closed
Sense wire shorted to another live circuit
Miswired retrofit gas installation feeding voltage back

Symptoms

  • Check engine light, depending on calibration
  • Battery drained after standing
  • Relay clicks are missing at ignition off

Repair estimate

DifficultyMediumDIY possible
Parts and labour€20–300
Time0.5–2 h

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

Parts involved

afcm power relayafcmwiring harness

Related codes

P2A35P2A36P2A34P0690

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