P218E: Throttle/Fuel Inhibit B Circuit High

P218E says the inhibit B line carries more voltage than the controller allows, typically because it touches a battery-fed wire or the sending unit's output stage is stuck high. No manufacturer documents P218E publicly. On the A line, GM's 2005 table for the 3.5-litre V6 (L66) uses two limits for P2555: more than 10 V with the ignition on, or more than 4.5 V once the ignition is off, each judged over 4 seconds; the check runs after shutdown and the MIL lights on the next drive cycle. The lower limit with the ignition off shows that the line should be nearly dead when the system sleeps. California's OBD rule requires such range checks. Look for chafing against supply wires, a backfeed through a faulty module or a shorted relay. P218D is the low-side counterpart.

Low severity. Can I keep driving?You can normally keep driving. If it affects the fuel level, do not trust the gauge and refuel earlier than usual.

Symptoms

Check engine lamp on the following drive
Possible power reduction

Most likely causes

Inhibit B wire shorted to a battery-fed circuit
Voltage fed back through a faulty module after ignition off
Relay contacts welded, keeping the line energised

What to check, in order

Start with the simplest. You can tick off each step.

Check the connector and wiring
Check the sensor's ground and make sure the signal wire is not receiving voltage from another circuit.
Use live data to compare the reading with actual conditions
Measure power, ground, and signal
Replace the sensor if the circuit is good

Good to know

Repair difficulty: medium
It can trigger limp mode.
It affects emissions.

What each character of P218E means

P: Powertrain: engine and transmission
2: Generic code: same on every make
1: Air and fuel
8E: Specific fault in that system

Frequently asked questions

Can I keep driving with code P218E?

You can normally keep driving. If it affects the fuel level, do not trust the gauge and refuel earlier than usual.

What causes code P218E?

The most common causes are: inhibit B wire shorted to a battery-fed circuit; voltage fed back through a faulty module after ignition off; relay contacts welded, keeping the line energised.

Related codes

Sources

Values and procedures vary by manufacturer. If it affects brakes, steering, fuel or high voltage, see a professional. Updated: 2026-11-04. How we build these pages.