Skip the auto shop - Our mechanics make house calls

P0120 OBD-II Trouble Code: TPS "A" Circuit Malfunction

check engine light logo

P0120 code definition

Throttle Pedal Position Sensor/Switch (TPS) "A" Circuit Malfunction

What the P0120 code means

P0120 is the generic OBD-II code which indicates that the Engine Control Module (ECM) has seen the TPS sensor circuit A output voltage going below or above the sensor's expected range, or is chattering when compared to TPS sensor circuit B.

What causes the P0120 code?

  • The ECM detected that the output from TPS sensor circuit A went outside of the specified voltage range in relation to TPS sensor circuit B.

  • The TPS sensor circuit A output falls below .2 volts or goes above 4.5 volts.

What are the symptoms of the P0120 code?

  • The ECM turns on the Check Engine Light and goes into failsafe mode by cutting the current to the throttle actuator to put the throttle valve at approximately less than 6 degrees opening.

  • The ECM controls fuel injection and timing to control engine speeds.

  • The vehicle would be able to be driven very slowly with limited throttle response.

  • The engine may idle higher than normal, but will not accelerate properly.

Note: The symptoms are determined by the manufacturer failsafe ECM strategy for the vehicle during a failure and may vary between manufacturers and vehicles.

How does a mechanic diagnose the P0120 code?

  • Scans and documents the codes received and views the freeze frame data to see when the code was set

  • Resets the codes to clear the OBD-II fault codes and retests the vehicle to see if the code comes back

  • Visually checks all of the TPS connections and wiring for any loose or damaged items.

  • Compares the data between TPS circuit A and B with a scanner, and if incorrect, replaces the TPS as directed by the pinpoint testing.

Common mistakes when diagnosing the P0120 code

  • Not performing a visual inspection first

  • Not scanning, documenting, clearing, and retesting for codes to verify failures

  • Not replacing an TPS sensor when tests indicate a problem

  • Not comparing TPS sensor A and B to be within specification before and after repair or replacements

How serious is the P0120 code?

The P0120 code will put the engine ECM to go into a failsafe mode, which will cause various drive complaints until repairs are done. For example, lack of acceleration, high idle, bucking or jerking, limited speeds, and possible stalling depending on the manufacturer failsafe mode strategy.

What repairs can fix the P0120 code?

Additional comments for consideration regarding the P0120 code

  • The P0120 code may be accompanied by other TPS codes, so following the manufacturer pinpoint tests for each code received may be needed to fix the complaint.

  • Most failures for code P0120 involve a defective TPS sensor not tracking the throttle angle correctly.

  • All TPS related codes will enable the failsafe mode and cause the same drive symptoms.

Need help with a P0120 code?

YourMechanic offers certified mobile mechanics who will come to your home or office to diagnose and repair your vehicle. Get a quote and book an appointment online or speak to a service advisor at 1-800-701-6230.

The statements expressed above are only for informational purposes and should be independently verified. Please see our terms of service for more details
Icon-warranty_badge-02

Skip the repair shop, our top-rated mechanics come to you.

At your home or office

Choose from 600+ repair, maintenance & diagnostic services. Our top-rated mechanics bring all parts & tools to your location.

Fair & transparent pricing

See labor & parts costs upfront, so you can book with confidence.

12-month, 12,000-mile warranty

Our services are backed by a 12-month, 12,000-mile warranty for your peace of mind.

Get A Quote

Need Help With Your Car?

Our certified mobile mechanics make house calls in over 2,000 U.S. cities. Fast, free online quotes for your car repair.

GET A QUOTE

More related articles

P0222 OBD-II Trouble Code: Throttle/Pedal Position Switch/Sensor B Circuit Low Input
P0222 code definition Throttle/Pedal Position Switch/Sensor B Circuit Low Input What the P0222 code means The manufacturer specifies a range of acceptable voltage to be produced from the throttle position...
Insurance Requirements for Car Registration in Kentucky
The Kentucky Transportation Cabinet requires that all drivers in Kentucky carry liability automotive insurance, or “financial responsibility” in order to operate a vehicle legally and maintain vehicle...
P0291OBD-II Trouble Code: Cylinder 11 Injector Circuit Low
P0291 code definition When your vehicle’s PCM registers the P0291 code, it means that a voltage reading came from the fuel injector circuit – for cylinder number 11’s fuel injector –...


Related questions

Q: Service engine soon light

The code P0325 and P1447 may be problems with the evaporative emission charcoal canister and vent solenoid problem from charcoal getting into the solenoid and tripping the code P1447. Some owners also got the code P0325 for the knock sensor...

Q: Transmission only has 1st gear

Hello. P0732 is the trouble code for an abnormal gear 2 shift ratio. If the vehicle's transmission computer detects that there is an issue with the gear ratio and timing of second gear, it will set off this code to...

Q: What are these codes that appeared on my car?

These codes are related to the engine sensors for mass air flow, idle air control, and the throttle position sensor. It is quite likely, given your mileage, that their sensors have become dirty/clogged, or the sensors have failed. You don't...