P2108 The throttle actuator control module reports that its performance is not what the engine computer expects

Throttle actuator control module performance

P2108 in short

P2108 means the throttle actuator control module, the electronics that run the throttle motor, is not performing as the engine computer expects. Wiring, a power relay, the throttle position sensors or the module are the usual causes. Many cases cut engine power, so get it diagnosed soon.

Some drive-by-wire systems use a separate throttle control module, and the main computer checks its performance. If the throttle position does not agree with what was requested, P2108 is set.

TroubleCodes.net lists wiring and connectors, throttle and pedal sensors, the throttle control module, the motor, the control relay and, rarely, the PCM. A 2025 Civic Hybrid report states the diagnostic recommended replacing power relay(s).

GM has several bulletins that list P2108 with reduced engine power on 2004 Cadillac models and 2006-2007 trucks and SUVs, and Mazda has a PCM reflash program on the 2004 RX-8. The NHTSA summaries do not describe the GM repairs.

Most likely causes

  1. Wiring, connectors or the throttle control power relay

    Common general cause
    Why it ranks here
    TroubleCodes.net lists poor connections and the control relay, and a Civic Hybrid diagnostic recommended replacing power relay(s).
    What would change this
    Rises if relay voltage drops or connectors are loose. Falls if power and grounds test steady.

  2. Throttle control module or throttle body

    Common general cause
    Why it ranks here
    The code is about this module's performance, so the module, motor or sensors inside the throttle body are listed causes.
    What would change this
    Rises if wiring and relay are good and throttle position does not follow the request. Falls if the throttle follows commands.
    How to test the electronic throttle body

  3. Engine computer software or module faults on certain models

    Supported by vehicle data
    Why it ranks here
    Mazda's 2004 RX-8 program uses a PCM reflash for lack of power with P2108, and GM issued several bulletins for P2108 on 2004 Cadillac and 2006-2007 trucks. Summaries are unverified.
    What would change this
    Rises on a covered model. Falls on others.
    How to test the engine control module (ecm / pcm)

What to test first

Start at step 1. Each result tells you what it means and where to go next.

  1. Read all codes. Note P2107, P1516, U0107 or P1659 stored with P2108, which point to the throttle module, its power feed or communication.

    Low riskTool: OBD-II scan tool

    • IfSeveral throttle module codes are stored

      It meansCheck the module's power and connectors and ask about bulletins for your model.

      Go to step 2

    • IfP2108 alone

      It meansCheck the power and wiring.

      Go to step 2

  2. Have a shop check the throttle control relay, power and ground feeds and connectors at the throttle body and module.

    Best left to a shopTool: multimeter, scan tool

    Warning:The throttle can move on its own when powered. Keep hands clear of the throttle plate and do not probe live circuits without the right tools.

Symptoms

  • Check engine light, sometimes with a traction control light
  • Rough idle or poor performance
  • Reduced engine power or limp mode Gets more serious: stop and have it checked.

How to fix

Parts and cost context

  • Electronic throttle body:Test the relay, wiring and bulletins before replacing the throttle body or module. Labour varies; get a quote.

Labor varies by vehicle and shop; get a quote before you approve a repair.

Compare used part prices on PartPriceGuide

On your vehicle

Mazda

  • 2004 · RX-8

    Supported by vehicle data

    Mazda special program MSP04 reflashes the PCM for lack of power with P2108. Whether it is still current is not verified.

  • MSP04Status unverified

    Special program, P2107/P2108/P2402/P0420 PCM reflash

    2004rx-8 · NHTSA 10008057

    Engine no start or lack of power with DTCs P2107, P2108, P2402 or P0420; PCM reflash.

    We couldn't confirm whether this bulletin is still current, so it doesn't count as confirmation.

No curated relationships for P2108 yet.

All Electronic throttle and accelerator pedal codes

P2108 questions

Is P2108 a bad throttle body?

Sometimes, but wiring, the power relay and software are also on the list. One 2025 Civic Hybrid report had the diagnostic recommend power relay replacement.

Sources and review

  1. P2108 trouble code page — TroubleCodes.net
  2. GM bulletin 06-06-04-042 (NHTSA 10020880) — NHTSA manufacturer communications database
  3. NHTSA complaint ODI 11561610: 2004 GMC Yukon — NHTSA Office of Defects Investigation
  4. NHTSA complaint ODI 10574183: 2005 Cadillac STS — NHTSA Office of Defects Investigation
  5. NHTSA complaint ODI 11768886: 2025 Honda Civic Hybrid — NHTSA Office of Defects Investigation
  6. GM bulletin 01503A (NHTSA 10004410) — NHTSA manufacturer communications database
  7. Mazda Special Program MSP04 (NHTSA 10008057) — NHTSA manufacturer communications database
Last reviewed
Written by
Saurabh K.
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