P1126
Throttle Position Narrow Range Sensor Circuit.
- Mazda
- Powertrain
- Manufacturer code
- Medium severity
How this code is built
- P
- SystemPowertrain
- 1
- Defined byThe manufacturer
- 1
- AreaFuel and air metering
- 26
- FaultThe specific fault in that area
What it means
On Mazda, P1126 relates to the throttle position sensor circuit, specifically the narrow range sensor signal. The engine control unit has seen a throttle position signal that is out of range, erratic or does not agree with expected values for engine load and airflow. The exact signal and test criteria vary by model and engine, so confirm against the manufacturer data for the vehicle.
Symptoms
- Check engine light on
- Unstable or hunting idle
- Hesitation or flat spot when pulling away
- Poor or inconsistent throttle response
- Engine may enter a reduced power or limp mode on some models
- Automatic gearbox shifting harshly or at odd times on some models
Possible causes
- Worn or faulty throttle position sensor or throttle body assemblylikely
- Damaged, chafed or corroded wiring in the sensor circuit (open circuit, short to earth or short to voltage)likely
- Loose, corroded or contaminated connector at the throttle body or control unitlikely
- Faulty sensor reference supply or earth shared with other sensorspossible
- Carbon build-up on the throttle plate or bore causing abnormal throttle movement and readingspossible
- Engine control unit faultrare
How to diagnose
- Read all stored and pending codes and freeze frame data, noting engine speed, load and throttle angle when the fault set, and check for any other sensor or reference voltage codes.
- Visually inspect the throttle body connector and wiring for damage, chafing, water ingress, corrosion or bent pins.
- Check the throttle body for heavy carbon deposits and for smooth, unobstructed plate movement (engine off, following the model's guidance on electronic throttles).
- With a scan tool, watch the live throttle position signal while slowly opening and closing the throttle; look for dropouts, spikes or a signal that does not follow pedal movement.
- Check the sensor reference voltage and earth at the connector against the manufacturer's specification.
- Test the signal wire for continuity and for shorts to earth or voltage between the sensor and control unit, with the battery disconnected.
- Check the accelerator pedal signals and compare them with the throttle readings where the model uses drive-by-wire.
- Check for any technical service bulletins or calibration updates relevant to the model and engine.
How to fix
- Repair or replace damaged wiring and ensure the repair is properly sealed and routed.
- Clean, repair or replace corroded or loose connector terminals.
- Replace the throttle body or throttle position sensor if the signal is erratic or out of specification, then carry out any throttle adaptation or relearn procedure the model requires.
- Clean carbon deposits from the throttle body using a suitable cleaner, taking care not to damage coatings or electronics.
- Repair the reference supply or earth fault found during testing.
- Replace or reprogram the engine control unit only after all wiring and sensor faults are ruled out and the manufacturer confirms it is necessary.
Can I keep driving?
The car can usually be driven carefully for a short time, but erratic throttle response can be unsafe in traffic and the fault may worsen. Book a diagnosis soon, and stop driving if the car loses power unpredictably or enters limp mode.
Guide written by AI from the code's definition. Confirm with a diagnosis before replacing parts.