Throttle/Pedal Position Sensor/Switch B Circuit Low

What it means

The engine computer has detected that the B signal voltage from the throttle position sensor or accelerator pedal sensor is below its minimum allowed value. This is usually caused by an open in the reference or signal wire or a short to ground, and the engine enters limp mode.

Related codes: P0220P0223P0122P2135P0641

Symptoms4

• Check engine light on with a reduced power message or light.
• Very weak acceleration or no response to the pedal.
• High or fixed idle speed on some vehicles.
• Codes for other sensors sharing the same reference voltage may also appear.

Possible causes6

• Unplugged or corroded sensor connector.
• Open in the reference voltage wire or the B signal wire.
• Signal wire shorted to ground.
• Internal failure of the sensor itself.
• A shorted sensor sharing the same reference voltage pulling it down.
• Reference voltage circuit fault inside the engine computer (rare).

How to diagnose5

1. Watch the B signal voltage on a scan tool; a reading near zero means an open or short to ground.
2. Measure the reference voltage at the sensor connector with the ignition on and compare it with the specification.
3. If the reference voltage is low, unplug the sensors that share it one at a time to find the one pulling it down.
4. Check continuity of the signal wire and its isolation from ground between the sensor and the computer.
5. Wiggle the wiring while watching to catch an intermittent open.

How to fix5

1. Reseat, clean or replace the connector.
2. Repair the reference or signal wire that is open or touching ground.
3. Replace another sensor proven to be pulling down the reference voltage.
4. Replace the pedal sensor or the throttle body assembly depending on where the fault is, then perform the relearn.
5. Clear the codes, then road test and confirm the code does not return.

Repair cost

In Saudi riyals; the highlighted part is the expected range for this fault.

The cost is low for a connector or wire repair, rises for a pedal sensor, and reaches the upper end when the electronic throttle body assembly is replaced.

Prices are rough estimates for common cars at independent workshops and vary with the car and the source of the part.
Prices last updated: September 2026

Frequently asked questions