What it means
The control module monitors whether tank select valve B responds as commanded to select the alternative fuel tank. It sets this code when the valve’s operation does not match the expected response.
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 systems may use several tank-select valves to route fuel from the chosen tank. The control module commands valve B and monitors the circuit or system response; this code sets when valve B does not behave as expected, such as sticking in its last position or moving too weakly.
Common causes
Most likely first.
- Valve stuck in last commanded position
- Coil force degraded
Symptoms
- Check-engine or alternative-fuel system warning light, if equipped
- Difficulty switching fuel tanks
- Loss of power or stalling
How to diagnose it
- Check freeze-frame data and alternative-fuel system live data to see when valve B was commanded and whether tank selection or fuel delivery changed.
- Inspect valve B, its connector, and nearby wiring for damage, contamination, loose fit, or signs that the valve is stuck.
- Use a scan tool’s supported output test to command valve B and observe whether the system response changes as expected.
- Check valve B’s control circuit and coil for continuity, shorts, and poor connections, following the vehicle wiring diagram.
- If the circuit checks out, investigate mechanical binding or weakened valve action using the manufacturer’s diagnostic procedure.
Common fixes
- Repair a loose, damaged, or contaminated valve B connector or wiring.
- Free or replace valve B if it is stuck or binding.
- Replace valve B if its coil or mechanical action is weak.
- Clear the code and verify valve B switches tanks correctly.
Can I keep driving?
Driving may be unreliable if the system cannot select the intended tank, and power loss or stalling can occur. Avoid trips that depend on switching tanks until the fault is diagnosed.
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.