P2A22

Code

Generic P — Powertrain

Alternative Fuel Tank Shutoff Valve B Control Circuit/Open

Brand: Generic

Type: P — Powertrain

Views: UK: 22 EN: 51 RU: 22

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Page language: EN

Causes

Open or high-resistance wiring in the valve control circuit
Disconnected, corroded, or damaged connector at the valve
Faulty Alternative Fuel Tank Shutoff Valve B (coil open)
Blown fuse or faulty relay for the alternative fuel shutoff circuit
Poor or missing ground
Faulty engine/vehicle control module (ECM/PCM) or driver output

Symptoms

Malfunction Indicator Lamp (MIL) or Check Engine Light ON
Alternate fuel system may not switch on or supply fuel
Vehicle may default to backup fuel or enter limp/limited mode
Reduced drivability or hesitation when trying to use alternative fuel
Diagnostic trouble code stored in ECM

What to check

Read and record trouble codes and freeze-frame using a scan tool; note commanded valve state
Visually inspect valve connector and wiring for damage, corrosion, or moisture
Verify fuses and relays related to the alternative fuel system
Backprobe valve connector and measure voltage while commanding valve ON/OFF with a scan tool
Measure coil resistance of the shutoff valve with connector disconnected
Perform continuity check from connector to ECM pin to verify open/high resistance

Signal parameters

Control type: typically a switched 12 V supply or switched ground driver from the ECM; some systems use PWM.
Expected voltage: when commanded ON, backprobe should show battery voltage or switching waveform; when OFF, 0 V or no drive depending on system design.
Coil resistance: typical solenoid coil resistance usually falls in a low-ohm range (commonly a few ohms to a few dozen ohms); an open coil will show infinite/very high resistance.
PWM: frequency and duty vary by manufacturer if PWM is used; check manufacturer service data for exact values.
No-load current: when driven ON, the circuit should draw measurable current consistent with coil resistance; an open circuit will show no current flow.

Diagnostic algorithm

Retrieve all stored codes and freeze-frame data. Confirm P2A22 and look for related codes (valve A, shorts, or communication errors).
Visually inspect the routing, clips, and connector of Alternative Fuel Tank Shutoff Valve B for damage, corrosion, or contamination. Repair as needed.
With ignition OFF, disconnect the valve connector and measure coil resistance across valve terminals. Compare to specification; infinite/high resistance indicates a failed valve.
Reconnect and backprobe valve connector. With scan tool, command valve ON and measure control voltage at the connector. Note whether the module is commanding and whether voltage/current is present.
If no voltage/drive is present when commanded, verify fuses/relays and check continuity between the valve connector and the ECM driver pin. Repair any open circuits or high-resistance wiring.
If drive voltage is present but valve coil is open, replace the shutoff valve and retest.
If valve and wiring check good but no proper command from ECM, inspect ECM driver output for shorts to voltage/ground and consider ECM testing/replacement only after wiring and components are confirmed good.
After repairs, clear codes, perform active tests if available, and road test to ensure the system operates normally and the code does not return.

Likely causes

Broken wire or chafed insulation between ECM and valve
Connector terminals pushed back, corroded, or contaminated
Valve coil open (infinite or very high resistance)
Fuse for fuel system driver circuit is blown
Damaged PCM output transistor or internal open circuit

Fault status

⚠️ Status

P2A22 — Alternative Fuel Tank Shutoff Valve B Control Circuit/Open: ECM commanded valve ON but detected an open/high-resistance circuit or no current flow. MIL set when fault confirmed.

🟡 Repair difficulty: Medium

⏱️ Diagnostic time: 0.5-2.0 hours