Powertrain, generic (extended)

P218D Throttle/Fuel Inhibit B Circuit Low

Check engine lightOn
EmissionsRelevant
Drive cycleRequired
Limp modePossible

P218D reports that the voltage on inhibit line B sits below the lowest permitted value, which normally points to a short to ground, a missing supply from the sending unit or an open line pulled down by the input stage. No manufacturer documents P218D publicly. For the A line, GM's 2005 table for the 3.5-litre V6 (L66) gives a concrete limit: P2554 is set when the analogue throttle inhibit circuit reads under 0.498 V for 4 seconds, with the check running after ignition off and the MIL lit on the next drive cycle. California's OBD rule requires out-of-range checks on such inputs. Chafed insulation touching body ground, water in a connector or a failed driver in the sending module are the likely causes. P218E is the opposite fault, P218B the general circuit code.

Likely causes

Inhibit B wire shorted to ground
Water or corrosion in a connector of the inhibit line
Output stage of the sending module failed

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

P218BP218CP218EP2554

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