P1126
Throttle Position (Narrow Range) Sensor Circuit Malfunction.
- Other
- 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
P1126 is a manufacturer-specific code. Where it is used for a throttle position (narrow range) sensor, the engine control unit has seen a signal from that sensor circuit that is out of range, erratic or does not agree with expected throttle or load. The narrow range sensor tracks small throttle openings near idle and light load in finer detail. Because the make is not specified, confirm the exact definition and test limits in make and model specific data before replacing parts.
Symptoms
- Engine warning light on
- Unstable or hunting idle
- Hesitation or poor response at light throttle
- Reduced power or limp mode
- Rough or surging engine at low speed
- Poor or harsh automatic gear changes on some models
Possible causes
- Faulty or worn throttle position sensorlikely
- Damaged, chafed or corroded wiring to the sensor (open circuit, short to earth or to voltage)likely
- Loose, corroded or contaminated connector terminals at the sensor or control unitlikely
- Dirty or sticking throttle body or worn throttle shaft giving an erratic signalpossible
- Fault in the sensor reference voltage supply or earth feedpossible
- Fault in the engine control unitrare
How to diagnose
- Read all stored and pending codes and record the freeze frame data, noting engine speed, load and temperature when the fault set.
- Look up the code definition and test values for the specific make, model and engine.
- Visually inspect the sensor wiring and connectors for chafing, heat damage, water ingress, corrosion and bent or pushed-out pins.
- Inspect the throttle body for carbon build-up, sticking or play in the throttle shaft.
- With live data, watch the throttle position signal while slowly opening and closing the throttle and look for dropouts, jumps or a flat spot.
- 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, then check the sensor output across its range.
- Only once wiring and supply are proven good, consider the control unit, after checking for software updates or known faults for that model.
How to fix
- Repair or replace damaged wiring and fix poor connector terminals.
- Replace the throttle position sensor, or the throttle body assembly if the sensor is not supplied separately.
- Clean the throttle body using the manufacturer's method, then carry out any required throttle adaptation or relearn.
- Restore a correct reference voltage or earth by repairing the supply circuit.
- Repair or replace the control unit only after all other causes are ruled out, and code or adapt it as the manufacturer requires.
Can I keep driving?
The car can usually be driven carefully for a short time, but power may be reduced and idle or throttle response may be unpredictable. Get it checked soon, and avoid driving if it stalls or hesitates in traffic.
Guide written by AI from the code's definition. Confirm with a diagnosis before replacing parts.