P2135: Throttle/Pedal Position Sensor/Switch "A"/"B" Voltage Correlation
The two throttle position sensors that report how far the throttle is open are disagreeing with each other.
What P2135 means
Electronic throttle bodies use two position sensors, A and B, that move together with the throttle plate. One usually rises in voltage as the throttle opens while the other moves in a different pattern, so the computer can cross check them. RepairPal explains that when the computer detects a problem with these sensors or their circuit, it sets P2135, and may limit the vehicle to 20 mph or less in limp home mode because it can no longer trust throttle position. The most common causes are worn sensor tracks inside the throttle body, a dirty throttle body, and corroded or loose connectors and wiring. On some vehicles a pedal position sensor problem can set this code too. KBB warns against driving because you may not be able to control your speed properly. Shops graph both sensor voltages while slowly opening the throttle, look for dropouts or mismatches, and check the connector and wiring. Replacing the throttle body is the usual fix, followed by a throttle relearn.
Common symptoms
- Check engine light, often with a wrench or reduced power light
- Car stuck in reduced power (limp) mode
- Poor or no response to the gas pedal
- Rough or high idle
- Stalling in some cases
Most common causes
- Worn throttle position sensors inside the electronic throttle body
- Dirty or carbon-filled throttle body
- Corroded or loose throttle body connector
- Damaged wiring between the throttle body and computer
- Faulty accelerator pedal position sensor on some vehicles
- Engine computer fault (rare)
What to check yourself first
Inspect the throttle body connector for corrosion, a loose fit or bent pins. Check the harness near the throttle body for damage. Look for recalls or service bulletins, since some makers have issued them for throttle body problems.
Typical fixes and what they cost
| Fix | Typical cost | Note |
|---|---|---|
| Replace throttle body | $623-$766 | The two sensors are built into the electronic throttle body on most cars, so it is replaced as a unit. |
| Electrical diagnosis to find a wiring or connector fault | $122-$179 | Connector corrosion and wiring faults are common causes. |
| Check engine light diagnosis at a shop | $125-$183 | Includes cleaning the throttle body and relearning throttle positions. |
Typical US price ranges for parts and labor, not quotes. Your shop should confirm the cause with a diagnostic before replacing parts.
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Related codes
- P2138 Throttle/Pedal Position Sensor/Switch "D"/"E" Voltage Correlation
- P2101 Throttle Actuator "A" Control Motor Circuit Range/Performance
- P2119 Throttle Actuator "A" Control Throttle Body Range/Performance
- P0121 Throttle/Pedal Position Sensor/Switch "A" Circuit Range/Performance
- P0122 Throttle/Pedal Position Sensor/Switch "A" Circuit Low