Powertrain, generic (extended)

P218A Throttle Actuator B Control System - Idle Position Not Learned

Check engine lightOn
EmissionsRelevant
Drive cycleNot required
Limp modePossible

P218A is the throttle B counterpart of P2176: on engines with a second electronic throttle, usually one per cylinder bank, that second unit failed to learn its closed rest position. GM's 2023 table 23OBDG07 runs the same three-step learn for bank 2 as for bank 1. First the plate must reach the closed target within 1.5 %, then the motor has to press it onto the stop with enough duty cycle, and finally the stored voltages must fall inside 0.33-0.58 V for sensor 1 and 4.42-4.67 V for sensor 2; any failed step stores the code within one trip. No other manufacturer documents P218A publicly. Ice, carbon, a weak motor or wiring faults at throttle B are typical causes, and engine power may be limited. Electrical motor faults of throttle B use P210A.

Likely causes

Carbon or ice keeping throttle B off its closed stop
Weak motor or gear wear in throttle unit B
Position sensors of throttle B outside the learn window
Supply or signal wiring fault at throttle B

Symptoms

  • Check engine lamp
  • Uneven idle between the banks
  • Reduced power

Repair estimate

DifficultyMediumWorkshop job
Parts and labour€0–800
Time0.3–2.5 h

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

Parts involved

throttle actuator belectronic throttle body

Related codes

P2176P210AP2119

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