Powertrain, generic (extended)

P2A5F Alternative Fuel Tank B Level Sensor Circuit

Check engine lightOn

EmissionsRelevant

Drive cycleNot required

Limp modeNo

How the content of a second gas tank is measured depends on the fuel. CNG has no liquid surface, so the level is worked out from pressure, often corrected by tank temperature; GM's 2015 Impala Bi-Fuel shows full near 3,600 psi and empty near 400 psi. LPG, being liquid, allows a float whose magnet passes its position through the tank wall to a Hall element, as in Rochester's R3D dials. P2A5F is the general circuit fault of such a sender on tank B, without a low or high finding. No manufacturer documents P2A5F. Roush's propane trucks with two tanks use the petrol codes P2067 and P2068 for the second sender instead, and the gauge then shows only the primary tank. Start with plug, wiring and supply of the tank B sender.

Likely causes

Plug or wiring of the tank B sender faulty

Tank B level sender or Hall module defective

Reading module or data link to the engine module disturbed

Symptoms

Check engine light
Gauge ignores the content of tank B
Range estimate on gas too low

Repair estimate

DifficultyMediumWorkshop job

Parts and labour€80–700

Time0.5–3 h

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

Parts involved

alt fuel tank b level sensorwiring harnessafcm

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