Powertrain, generic (extended)

P2A5B Alternative Fuel Vaporizer C Outlet Temperature Sensor Range/Performance

Check engine lightOn

EmissionsRelevant

Drive cycleRequired

Limp modeNo

With three outlet sensors in one system, a plausibility check can use a majority: if A and B agree and C stands apart, vaporizer C or its sensor is the odd one out. P2A5B means the C value is electrically valid but fails such a comparison or does not follow warm-up and load as it should. The industrial vaporizer described in US6755643B2 shows the physical background: when more vapour is drawn than a unit can produce, its outlet cools. A C reading that sinks only under heavy load may therefore be true and point to a starved or fouled vaporizer (P2A8D) rather than to the sensor. A reading that stays flat whatever the engine does points to the sensor. No maker publishes the logic behind P2A5B.

Likely causes

Sensor C stuck, drifting or slow

Vaporizer C genuinely too cold from lack of coolant or fouling

Sensor without good thermal contact

Symptoms

Check engine light, depending on calibration
Power loss at full load on gas
Vaporizer C differs clearly from A and B in live data

Repair estimate

DifficultyMediumWorkshop job

Parts and labour€100–700

Time0.5–3 h

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

Parts involved

alt fuel vaporizer c outlet temp sensorwiring harnessafcm

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