Powertrain, generic (extended)

P218E Throttle/Fuel Inhibit B Circuit High

Check engine lightOn
EmissionsRelevant
Drive cycleRequired
Limp modePossible

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.

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

Symptoms

  • Check engine lamp on the following drive
  • Possible power reduction

Repair estimate

DifficultyMediumWorkshop job
Parts and labour€50–600
Time0.5–3 h

Typical range across vehicles; the real cost depends on what the testing finds.

Parts involved

throttle fuel inhibitwiring harness

Related codes

P218BP218CP218DP2555

References: gsi.ext.gm.com, law.cornell.edu.