P2A26

Code

Generic P — Powertrain

Alternative Fuel Tank Shutoff Valve C Control Circuit/Open

Brand: Generic

Type: P — Powertrain

Views: UK: 20 EN: 33 RU: 21

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Page language: EN

Causes

Open or high-resistance wiring in valve control circuit
Disconnected, corroded or damaged connector at valve or harness
Failed shutoff valve solenoid (open coil)
Blown fuse or faulty relay supplying valve circuit
Poor or corroded ground connection
PCM/ECM driver output fault

Symptoms

Malfunction Indicator Lamp (MIL) illuminated with stored DTC P2A26
Possible alternative-fuel system fault message or reduced functionality
Valve C may not open or close when commanded (fuel delivery or isolation issue)
No voltage change at valve connector when commanded
Possible drivability issues if fuel supply is affected

What to check

Use a scan tool to confirm P2A26 and review any related codes and freeze-frame data
Visually inspect valve C connector and wiring for corrosion, damage or disconnection
Check relevant fuses and relays for the alternative fuel valve circuit
Backprobe valve connector and command PCM output while commanding valve ON/OFF with scan tool
Measure coil resistance of the valve with connector disconnected
Check continuity from valve connector to PCM pin and to ground

Signal parameters

Expected coil resistance: typically in the low tens of ohms (commonly ~5–50 Ω) — consult vehicle manual for exact specification
Control signal behavior: PCM usually switches the circuit (low-side) — expected to toggle between near 0 V (ground) when energized and battery voltage (~12 V) when de-energized; some systems use a high-side driver instead
Current draw: typically hundreds of milliamps to a few amps depending on valve design
If PWM controlled: switching frequency often tens to a few hundred Hz and duty cycle changes when commanded (use a scope to verify)
No continuity (OL) or very high resistance at valve coil indicates open circuit

Diagnostic algorithm

Verify code with a scan tool and record freeze frame and related codes
Inspect harness and connector at Alternative Fuel Tank Shutoff Valve C for corrosion, bent pins, water intrusion or mechanical damage
Check fuses/relays related to the alternative fuel valve circuit; replace if blown and retest
With ignition ON (engine OFF) backprobe the valve connector: measure supply voltage and control/ground signal while commanding valve ON and OFF from the scan tool
If no command signal present at connector, measure at the PCM pin to confirm if PCM is issuing the command
Disconnect connector and measure valve coil resistance with an ohmmeter; compare to specification — open or infinite resistance indicates a failed coil
Perform continuity check between valve control pin and PCM pin; repair any open or shorted wiring found
If wiring and connectors are good but no operation, command the valve and use a lab scope to observe PCM driver waveform (look for proper switching or PWM)
If PCM is not commanding but wiring is intact, consider PCM driver fault and consult manufacturer procedures before replacement
After repair or part replacement, clear codes and verify proper operation through functional test and a short road test if applicable

Likely causes

Broken/disconnected control wire between PCM and valve
Corroded or pushed-out connector at the valve
Failed valve coil (open circuit)
Blown fuse or failed relay in valve power feed
Damaged wiring from chafing or rodent chew
PCM output driver fault (less common)

Fault status

⚠️ Status

P2A26 — Alternative Fuel Tank Shutoff Valve C Control Circuit/Open. The controller detected an open circuit or loss of continuity in the control wiring to the shutoff valve for alternative fuel tank C.

🟡 Repair difficulty: Medium

⏱️ Diagnostic time: 0.5-2.0 hours