Faulty throttle actuator control motor or throttle body assembly with carbon buildup or mechanical binding.; Damaged or corroded wiring and connectors in the throttle/fuel inhibit circuit B, including open or short circuits.; Failed accelerator pedal position sensor or its associated wiring, sending implausible signals to the PCM.; Defective fuel pump control module or fuel pump inertia switch causing intermittent inhibit signals.; PCM software calibration issue or internal fault in the throttle control driver circuit.; Aftermarket electronic throttle controllers or piggyback tuners interfering with factory inhibit signals.; Poor ground connections at the chassis or engine block affecting circuit reference voltage.

DTC codes / P21xx · Fuel and air metering / P218C

P218CThrottle/Fuel Inhibit B Circuit Range/Performance

Q: What does code P218C mean?

Throttle/Fuel Inhibit B Circuit Range/Performance. P218C indicates that the powertrain control module (PCM) has detected an out-of-range condition in the throttle or fuel inhibit circuit B, which is used to cut fuel or throttle during certain safety or emissions events. The computer compares expected voltage or performance from this circuit against actual values and sets the code when the signal falls outside the manufacturer's calibrated range for a specified time.

P218C indicates that the powertrain control module (PCM) has detected an out-of-range condition in the throttle or fuel inhibit circuit B, which is used to cut fuel or throttle during certain safety or emissions events. The computer compares expected voltage or performance from this circuit against actual values and sets the code when the signal falls outside the manufacturer's calibrated range for a specified time.

SystemPowertrain

Code typeGeneric (all makes)

SeverityMedium

Fix difficultyIntermediate

AreaFuel and air metering

Symptoms you may notice

Illumination of the check engine light, often with no other noticeable symptoms.
Reduced engine power or limp mode, where the throttle response becomes sluggish or limited.
Unexpected engine stall or difficulty restarting after a fuel cut event.
Poor acceleration or hesitation when demanding power, especially under load.
In rare cases, the engine may idle roughly or surge if the inhibit circuit affects fuel delivery.

Common causes, most likely first

Faulty throttle actuator control motor or throttle body assembly with carbon buildup or mechanical binding.
Damaged or corroded wiring and connectors in the throttle/fuel inhibit circuit B, including open or short circuits.
Failed accelerator pedal position sensor or its associated wiring, sending implausible signals to the PCM.
Defective fuel pump control module or fuel pump inertia switch causing intermittent inhibit signals.
PCM software calibration issue or internal fault in the throttle control driver circuit.
Aftermarket electronic throttle controllers or piggyback tuners interfering with factory inhibit signals.
Poor ground connections at the chassis or engine block affecting circuit reference voltage.

How to diagnose and fix it

Connect a scan tool and record all stored codes, freeze-frame data, and live throttle/fuel inhibit parameters to understand when the fault occurs.
Visually inspect the throttle body, accelerator pedal assembly, and related wiring for obvious damage, corrosion, or loose connectors.
Perform a voltage drop test on the inhibit circuit B wiring and grounds to check for excessive resistance or open circuits.
Clean the throttle body and perform a throttle relearn or calibration procedure using the scan tool.
Test the throttle actuator motor and accelerator pedal position sensors with a multimeter or oscilloscope for smooth, linear signals.
If wiring and components test good, reflash or update the PCM calibration per manufacturer service information.
Replace the faulty component (throttle body, pedal sensor, or fuel pump control module) only after confirming the defect with diagnostic tests.

When the throttle body is not the culprit

A dirty throttle body often causes P218C without any hard failure, so cleaning and relearning the throttle position is frequently the fix before replacing parts.
Corroded grounds or a weak battery can produce intermittent inhibit circuit codes that mimic a failed throttle actuator, so always check charging system health first.
Aftermarket throttle controllers or performance tuners can interfere with the inhibit circuit B signal and set this code even when all factory components are healthy.
The code may be stored alongside transmission or stability control codes because the PCM uses the inhibit circuit to coordinate torque reduction during shifts or traction events.
A failed fuel pump inertia switch or fuel pump control module can trigger P218C because the inhibit circuit B often controls fuel delivery during crash or safety events.

Can I keep driving with P218C?

You can usually drive the vehicle to a repair shop, but avoid aggressive acceleration or heavy loads because the throttle may enter limp mode unexpectedly. If the engine stalls or power reduction becomes severe, pull over safely and have the vehicle towed to prevent a hazardous loss of power.

Tools that help

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Guidance is general and written for all OBD-II vehicles. Exact tests and values vary by model, so confirm the fault before replacing parts.