Powertrain, generic (extended)

P2A36 AFCM Power Relay Sense Circuit Low

Check engine lightOn
EmissionsRelevant
Drive cycleNot required
Limp modePossible

P2A36 is set when the relay feeding the gas control module has been commanded on, yet the voltage read back after its contacts stays too low. Burnt or pitted contacts, a high-resistance joint, a grounded sense wire or a blown fuse in the switched path all lead there, as does a weak battery during cranking. For the comparable engine relay code P0689, GM Europe on the 2010 Saab V6 uses a limit of 6 V held for more than 1 s and treats the result as Type C. No public calibration names P2A36 for a gas system. If the module really runs short of voltage, it may reset or drop off the network, which Roush's Ford propane trucks report as U0108; in a bi-fuel car the engine then returns to petrol.

Likely causes

Worn or burnt relay contacts
Blown fuse in the switched supply
Sense wire shorted to ground
Weak battery or poor main ground

Symptoms

  • Check engine light, depending on calibration
  • Gas mode drops out, bi-fuel vehicle switches to petrol
  • Communication fault with the gas module stored as well

Repair estimate

DifficultyMediumDIY possible
Parts and labour€20–350
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

P2A35P2A37P2A33P0689P0562

References: law.cornell.edu, saabwisonline.com, roushcleantech.com.