Powertrain, generic (extended)

P2A35 AFCM Power Relay Sense Circuit

Check engine lightOn
EmissionsRelevant
Drive cycleNot required
Limp modeNo

Besides driving the relay coil, a control module can read back the voltage behind the relay contacts to confirm that power actually arrives. P2A35 is the general fault of this feedback line for the relay that supplies the gas control module, without a statement about too low or too high. Typical are an open sense wire, a corroded pin or a blown fuse between contact and sense point. Roush CleanTech's propane manual for Ford trucks lists a missing supply, a blown fuse or lost power and ground of its alternative fuel module as reasons for losing it on the bus (U0108), which shows how supply problems surface there. No published calibration uses P2A35; the engine-relay sibling P0688 is the analogue. Electrical symptoms may be absent while the relay itself still works.

Likely causes

Sense wire open or pin backed out
Blown fuse between relay contact and sense point
Corroded terminals in relay socket or module plug

Symptoms

  • Check engine light, depending on calibration
  • Often no drivability change
  • Occasional fallback to petrol if the supply really drops

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

P2A36P2A37P2A32P0688U0108

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