Faulty accelerator pedal position sensor (worn tracks or internal failure); Wiring harness damage (open, short, or chafed wires between APP sensor and ECM); Corroded or loose electrical connectors at the APP sensor or ECM; Poor ground connection for the APP sensor circuit; ECM internal fault (rare but possible); Aftermarket floor mats or debris obstructing pedal movement (indirect cause)

DTC codes / Toyota codes / P1120

P1120 · ToyotaAccelerator Pedal Position Sensor Circuit

Q: What does code P1120 mean?

Accelerator Pedal Position Sensor Circuit. P1120 on Toyota vehicles indicates a fault in the Accelerator Pedal Position (APP) sensor circuit, which the engine control module (ECM) uses to determine how far the driver is pressing the pedal. The ECM detects an abnormal voltage signal or correlation issue between the two APP sensor outputs and sets this code, often triggering reduced engine power mode.

P1120 on Toyota vehicles indicates a fault in the Accelerator Pedal Position (APP) sensor circuit, which the engine control module (ECM) uses to determine how far the driver is pressing the pedal. The ECM detects an abnormal voltage signal or correlation issue between the two APP sensor outputs and sets this code, often triggering reduced engine power mode.

SystemPowertrain

Code typeToyota specific

SeverityMedium

Fix difficultyIntermediate

AreaFuel and air metering

Symptoms you may notice

Illumination of the check engine light and possibly the vehicle stability control (VSC) or traction control light
Reduced engine power or limp mode, limiting vehicle speed
Hesitation or poor acceleration when pressing the accelerator pedal
Engine idle may be erratic or higher than normal
Often no symptoms besides the warning light, especially if the fault is intermittent

Common causes, most likely first

Faulty accelerator pedal position sensor (worn tracks or internal failure)
Wiring harness damage (open, short, or chafed wires between APP sensor and ECM)
Corroded or loose electrical connectors at the APP sensor or ECM
Poor ground connection for the APP sensor circuit
ECM internal fault (rare but possible)
Aftermarket floor mats or debris obstructing pedal movement (indirect cause)

How to diagnose and fix it

Scan all modules for stored codes and freeze frame data to confirm P1120 and check for related APP sensor codes
Visually inspect the APP sensor connector and wiring for damage, corrosion, or loose pins
Measure reference voltage (typically 5V) and ground at the APP sensor connector with the key on
Check the APP sensor signal voltage while slowly pressing the pedal, looking for smooth progression without drops or spikes
Perform a wiggle test on the harness while monitoring live data to detect intermittent connections
If the sensor signal is erratic or out of specification, replace the accelerator pedal assembly (sensor is usually integrated)
Clear codes and perform a road test to verify the repair, ensuring the ECM relearns the pedal position

Common Misdiagnosis Traps for P1120

A weak or failing battery or charging system can cause voltage irregularities that mimic APP sensor faults, so always check battery health first.
The APP sensor is often integrated into the accelerator pedal assembly, so replacing just the sensor may not be possible; the entire pedal may need replacement.
Intermittent P1120 codes can be caused by a poor ground connection at the ECM or chassis, which is often overlooked during diagnosis.
Aftermarket floor mats that interfere with pedal travel can set this code by preventing the pedal from returning to its rest position.
The ECM may set P1120 even when the sensor is functioning correctly if the correlation between the two APP sensor signals is off due to a mechanical issue like a sticking pedal.

Can I keep driving with P1120?

If the vehicle is in limp mode, avoid driving at high speeds or under heavy load, and have it diagnosed promptly. If the check engine light is on but the car drives normally, you can drive cautiously to a repair shop, but do not ignore the warning as the fault may worsen.

Tools that help

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Guidance is general and written for Toyota vehicles. Exact tests and values vary by model, so confirm the fault before replacing parts.