Powertrain, generic (extended)

P218B Throttle/Fuel Inhibit B Circuit

Check engine lightOn
EmissionsRelevant
Drive cycleRequired
Limp modePossible

P218B is a general electrical fault in the second throttle/fuel inhibit line, B. An inhibit line carries a signal with which another unit can tell the engine computer to keep the throttle closed or stop fuelling. No manufacturer documents the B line publicly. The only published use of this function concerns the A line: GM's 2005 table for the 3.5-litre V6 (L66) places it in the throttle valve control section, where the injection and throttle processors check each other, and monitors it with P2553-P2555 once per drive cycle after ignition off, lighting the MIL on the next drive cycle. California's OBD rule requires inputs of this kind to be checked for circuit faults. Open wires, corroded pins and module connector faults come first; reduced power is possible.

Likely causes

Open or high-resistance inhibit B wire
Corroded or loose pins at the engine or throttle module connector
Fault in the unit that drives the inhibit signal

Symptoms

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

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

P218CP218DP218EP2552

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