Skip to content
Skip to content

OBD-II Code

P1129

Severity

Not yet reviewed

Nobody on our side has assessed this code yet, so we are not going to guess at how serious it is.

Can you drive it

We cannot say

Treat it as unknown until a shop reads it with live data. If the check-engine light is FLASHING, stop driving as soon as it is safe to — that means an active misfire, whatever the code.

Indicative cost (USD)

$80–$550

From this code's diagnostic notes. Varies by vehicle, diagnosis, parts, and local labor. This is not a repair quote.

P1129 on a Toyota is the general Electric Throttle Control System Malfunction set — it's the catch-all ETCS-i code that sets when the ECM has detected a fault inside the throttle control logic that doesn't fit cleanly into P1125 (motor circuit), P1127 (power source), or P1128 (motor lock).

How a shop works this

Work from evidence to part, not the other way round. A code names a circuit or a symptom; it does not name the part that failed.

  1. Note every code that is set, not just this one.

    Codes that appear together usually narrow the cause faster than any one of them read alone.

  2. Read the freeze frame — the conditions the fault was recorded under.

    Cold or warm, idle or load, road speed and engine speed. A fault that only appears cold is a different fault from one that only appears under load, even with the same code on the scanner.

  3. Confirm the fault is current rather than history.

    Clear the code and see whether it returns under those same conditions. A code that does not come back may have been logged during a repair, a flat battery, or a bad connection that has since been disturbed.

  4. Then follow the diagnostic notes further down this page, in the order they are written.

    They are written in the order a shop works this code, cheapest checks first. Where they name a component, inspect its wiring and connector before replacing it.

If the code comes back after a repair, the underlying fault is still there. That is the point to bring in a scanner with live data and freeze-frame, or a shop that has one.

Common symptoms

  • Check engine light
Read the full diagnostic procedureP1129 on a Toyota is the general Electric Throttle Control System Malfunction set — it's the catch-all ETCS-i code that sets when the ECM has detecte…

P1129 on a Toyota is the general Electric Throttle Control System Malfunction set — it's the catch-all ETCS-i code that sets when the ECM has detected a fault inside the throttle control logic that doesn't fit cleanly into P1125 (motor circuit), P1127 (power source), or P1128 (motor lock). Common triggers: TPS1 and TPS2 disagreement greater than 10% of full-scale (the throttle body carries dual redundant TPS sensors and the ECM cross-checks them constantly), an internal H-bridge driver fault inside the ECM, or a software watchdog timeout in the throttle control loop.

Cheapest-first ladder

  1. scan live data for TPS1 and TPS2 voltages with key on and the pedal slowly swept from rest to wide-open — both signals should track in opposite directions (one rising 0.5V to 4.5V, the other falling 4.5V to 0.5V on most Toyota ETCS-i variants) with <3% disagreement at any single sample point. If they diverge more than 10% at any blade angle, the TPS pair is the fault.
  2. Inspect the throttle body harness for chafing or a partial short — a single broken TPS signal wire often presents as P1129 because both sensors share the harness path to the ECM.
  3. Confirm 5V reference at the TPS connector (should be 4.9-5.1V); a sagging 5V reference can pull both TPS readings toward each other and trigger the cross-check fault without either sensor being independently bad. Expensive-misdiagnosis caveat: don't replace the ECM for P1129 — Toyota ECMs almost never fail internally in a way that throws P1129; the fault is in the throttle body (TPS pair) or the harness about 95% of the time, and a $1,200 ECM is the wrong answer when a $400 throttle body or $40 harness repair would have closed it.
Vehicle-specific patterns2002-2011 Camry 2.4L (2AZ-FE) and 3.0/3.5L (1MZ-FE, 2GR-FE) throw P1129 most often from TPS pair drift around 120K-150K mi — the dual potentiometers…
  • 2002-2011Camry 2.4L (2AZ-FE) and 3.0/3.5L (1MZ-FE, 2GR-FE) throw P1129 most often from TPS pair drift around 120K-150K mi — the dual potentiometers wear unevenly as the blade cycles.
  • 2004-2013Highlander 3.3/3.5L (3MZ-FE, 2GR-FE) and 2004-2010 Sienna 3.3/3.5L share the same TPS architecture and the same drift pattern.
  • 2007-2012RAV4 2.5L (2AR-FE) throws P1129 with a slightly later mileage onset (~140K-180K mi) and the TPS replacement is the durable fix.
  • 2006-2013Lexus IS250/IS350 (4GR-FSE, 2GR-FSE) and GS350 (2GR-FSE) throw P1129 with similar timing — Lexus throttle bodies are the same part-family as Toyota's and fail the same way.

Estimated repair$80 to $550.

Look up another code

More free tools

VIN DecoderDecode year, make, model, engine, recalls.Maintenance ScheduleOil, timing belt, fluids, by vehicle.Tire SizeOEM vs new — diameter delta + speedo error.Gas CostWeekly, monthly, annual fuel math.

See all 9 tools