What it means
A general electrical fault on the throttle/fuel inhibit signal B — used by anti-theft, immobiliser, or transmission to forbid throttle/fuel until released.
At a glance
- Usually lights the check-engine light
- Affects emissions; the car can fail an emissions test
How it works
The throttle/fuel inhibit B circuit carries an enable or inhibit signal used by a vehicle system, such as security or transmission control, to prevent throttle or fuel operation under certain conditions. P218B sets when the module detects an electrical fault in that B signal circuit, which can prevent normal starting or power delivery.
Common causes
Most likely first.
- Open, shorted, or damaged inhibit signal wiring
- Poor connection at a connector or terminal
- Fault in the module or system providing the inhibit signal
- Fault in the receiving throttle or fuel-control circuit
Symptoms
- Check engine light on
- Engine may crank without starting or fail to start
- Reduced throttle response or engine power
- Security or transmission warning light may come on
How to diagnose it
- Record freeze-frame data and scan all relevant modules for related security, transmission, or throttle/fuel inhibit codes to identify which system reported the fault.
- Inspect the B inhibit circuit connectors and accessible wiring for loose terminals, corrosion, damage, or signs of tampering.
- Check live data or module status for whether the inhibit B signal is being commanded and received as expected.
- Test the inhibit B circuit for opens, shorts, and poor connections using the vehicle wiring diagram and manufacturer's procedure.
- If wiring checks out, diagnose the module providing the inhibit signal and the receiving throttle or fuel-control circuit using manufacturer-specific tests.
Common fixes
- Repair damaged or disconnected wiring in the throttle/fuel inhibit B circuit.
- Clean and secure poor connections at the relevant module connectors.
- Correct a confirmed security or transmission system fault preventing release of the B inhibit signal.
- Repair or replace a failed providing or receiving module only after circuit testing confirms the fault.
Can I keep driving?
If the engine will not start or throttle response is reduced, do not rely on the vehicle for a trip where stalling or loss of power would be hazardous. Have the inhibit fault diagnosed before normal use, especially if security or transmission warnings are present.
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.