Powertrain, generic (extended)

P2A9F Alternative Fuel Return Line Valve Control Circuit Range/Performance

Check engine lightOn
EmissionsRelevant
Drive cycleNot required
Limp modePossible

P2A9F covers the grey zone between a clean open and a clean short: the control circuit of the return line valve is connected, but the current or voltage the output stage measures while driving it does not fit the command. Typical reasons are a coil whose resistance has drifted, a few shorted windings, or high contact resistance in a corroded connector that lets the coil pull in only weakly or late. For a comparable tank solenoid the ROUSH CleanTech propane manual gives 6 to 35 ohms as the acceptable window, which is a useful benchmark when measuring. No manufacturer documents P2A9F or a threshold for it publicly. A valve that switches unreliably can leave vapor in the rail after a hot soak; a hydraulic lack of return flow with a sound circuit is P2AA2.

Likely causes

Solenoid coil resistance out of range or partially shorted windings
High contact resistance from corrosion or water in the connector
Low supply voltage at the valve from a weak relay contact or ground
Output stage of the fuel control module measuring incorrectly

Symptoms

  • Malfunction indicator lamp on
  • Occasional hard starts after a hot soak
  • Fault comes and goes with temperature or moisture

Repair estimate

DifficultyMediumWorkshop job
Parts and labour€40–500
Time0.5–3 h

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

Parts involved

alt fuel return line valvewiring harnessafcm

Related codes

P2A9EP2AA0P2AA1P2AA2

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