What it means
The control circuit of alternative fuel tank shutoff valve B reports a control circuit performance/stuck off condition. Tank isolation cannot be commanded as expected on multi-tank CNG/LPG systems.
At a glance
- Usually lights the check-engine light
- Affects emissions; the car can fail an emissions test
- The engine or gearbox may go into limp mode
How it works
Alternative-fuel tank shutoff valve B isolates its tank in a multi-tank CNG or LPG system. The control module monitors whether the valve responds as commanded and sets this code when valve B's operation is outside the expected range or appears stuck, even if its circuit is not fully open.
Common causes
Most likely first.
- Shutoff valve mechanically stuck closed
- Coil force degraded with age
- Carbon or debris buildup preventing free movement
Symptoms
- Check-engine light
- Alternative-fuel warning light
- Difficulty switching fuel modes
How to diagnose it
- Save freeze-frame data and review fuel-mode and valve B command or status data to identify when the valve fails to respond as expected.
- Inspect valve B's wiring and connector for damage, corrosion, or poor contact that could weaken its operation.
- Check the valve coil and control circuit against the manufacturer's specification to rule out an electrical cause.
- Use the manufacturer's procedure to verify whether valve B moves or changes state when commanded; do not bypass the fuel-system safety controls.
- If electrical checks pass, inspect or test the valve for sticking, contamination, or weakened mechanical action as specified by the manufacturer.
Common fixes
- Repair damaged wiring or poor connections at valve B.
- Clean or replace corroded valve B terminals.
- Replace the valve B coil if it fails the specified electrical test.
- Repair or replace valve B if it is confirmed stuck or unable to move as commanded.
Can I keep driving?
Avoid switching fuel modes repeatedly, and use only a mode the vehicle indicates is available. If the system cannot reliably isolate tank B, do not continue using the alternative-fuel system until the valve fault is resolved.
A code shows where the control module detected a fault, not always which part failed. Check the causes in order and confirm with a test before replacing parts. Have several codes? Check them together
This is a generic code: it means the same on every make. The car’s maker may add more detail in its own service information.