Powertrain, generic (extended)

P2A9A Alternative Fuel Tank Select Valve C Control Circuit Performance

Check engine lightOn

EmissionsRelevant

Drive cycleRequired

Limp modePossible

With P2A9A, select valve C passes its electrical tests, but the effect of switching does not show up as expected. The likely evidence is pressure: once vessel C is selected, its own tank pressure sensor should begin to fall with consumption and the pressure ahead of the regulator should match that vessel's level. If tank C stays untouched, or the pressure jumps to a value that fits another vessel, the valve has not moved or leaks internally. Cespira's patent shows why the selection matters, since its controller decides which supply goes to compression and which to the regulator from measured supply pressures. A partial fault may only appear in the cold. No manufacturer publishes P2A9A or the comparison it uses; P2A46 and P2A47 cover the tank C pressure sensor.

Likely causes

Valve C not shifting fully because of wear or contamination

Internal leakage letting vessel C feed in the wrong position

Faulty tank C pressure reading misleading the check

Symptoms

Malfunction lamp on
Tank C level hardly changes over a tank cycle
Fault appears mainly in cold weather

Repair estimate

DifficultyShop_onlyWorkshop job

Parts and labour€200–1,800

Time1.5–5 h

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

Parts involved

alt fuel tank select valve cwiring harnessafcm

References: law.cornell.edu, patents.google.com.