What it means
Voltage on the alternative-fuel disable control line is below the expected window. Usually a short to ground or a failed driver pulling the line low.
At a glance
- Usually lights the check-engine light
How it works
The alternative-fuel disable control circuit carries the command used to disable that fuel system, often when the engine switches to another fuel. The control module monitors the command line and sets this code when its voltage falls below the allowed range, commonly because the line is grounded or the module output is pulling it low.
Common causes
Most likely first.
- Disable control wire shorted to ground
- Low-side driver internally shorted
- Connector pins corroded - high contact resistance
Symptoms
- Alternative-fuel operation may be unavailable
- Engine may switch to or remain on the other fuel
How to diagnose it
- Use a scan tool to record freeze-frame data and compare the alternative-fuel disable command with the circuit status when the low reading occurs.
- With the ignition off, inspect the disable-control wire and connectors for crushed insulation, chafing, or contact with ground.
- Check the connector pins for corrosion, looseness, or poor contact that could affect the low-side circuit.
- With the circuit isolated as specified by the manufacturer, test the disable-control wire for a short to ground.
- If the wiring and terminals are sound, follow the manufacturer's procedure to check whether the low-side module driver is pulling the line down.
Common fixes
- Repair wiring shorted to ground or damaged insulation.
- Clean or repair corroded or loose connector terminals.
- Repair an open or damaged section of the disable-control wire.
- Replace or repair the control module if its low-side driver is confirmed faulty.
Can I keep driving?
Alternative-fuel operation may be unavailable, and the engine may switch to or remain on the other fuel. If the engine runs normally and there is no fuel leak, keep driving limited until the circuit is diagnosed; stop if drivability becomes unsafe.
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.