Short answer
P0120 circuit malfunction, P0121 range or performance, P0122 low input, P0123 high input, P0124 intermittent, and P2135 sensor A and B disagree (electronic throttles). Low and high input codes are often wiring; range and intermittent codes often point to a worn sensor; P2135 usually points to the electronic throttle body, its connector or the pedal sensor.
The six codes
Generic OBD-II throttle position codes. Titles from OBD-Codes.com; your maker may word them differently.
| Code | Generic title | In plain English | Guide |
|---|---|---|---|
| P0120 | Throttle Position Sensor/Switch A Circuit Malfunction | The signal is outside the range the computer expects. | P0120 guide |
| P0121 | Throttle Position Sensor/Switch A Circuit Range/Performance | The signal does not match what the engine is doing (RPM, airflow). | P0121 guide |
| P0122 | Throttle Position Sensor/Switch A Circuit Low Input | The signal voltage is too low, often an open or a short to ground. | P0122 guide |
| P0123 | Throttle Position Sensor/Switch A Circuit High Input | The signal voltage is too high, often a lost ground or a short to voltage. | P0123 guide |
| P0124 | Throttle Position Sensor/Switch A Circuit Intermittent | The signal drops in and out: wiring, a connector or a worn track. | Codes hub |
| P2135 | Throttle/Pedal Position Sensor/Switch A/B Voltage Correlation | The two sensors in an electronic throttle body disagree. | P2135 guide |
Read the last word first
Malfunction
P0120
The signal is outside its normal operating range. Broad, so check reference, ground and signal in turn. P0120 guide
Range/performance
P0121
The signal is in range but does not make sense for the RPM or airflow. Often a worn track. P0121 guide
Low input
P0122
Voltage too low. Think open signal or reference wire, short to ground, or a sensor not seated. P0122 guide
Intermittent
P0124
The signal drops in and out. Wiring, connectors, a worn track or a binding throttle plate. Covered below.
A/B correlation
P2135
The two throttle signals disagree. Connector, throttle body or pedal sensor. P2135 guide
P0124: throttle position sensor A circuit intermittent
- Code
- P0124
- Generic title
- Throttle Position Sensor/Switch A Circuit Intermittent
- Meaning
- The signal drops in and out: wiring, a connector or a worn track.
- Severity
- Medium
P0124 means the computer saw the sensor A signal drop in and out. OBD-Codes.com lists hesitation when accelerating, dark exhaust smoke, slow starts and worse fuel economy as possible symptoms, and gives these causes: a faulty or out-of-adjustment TPS, open or shorted wiring or connectors, a binding or damaged throttle plate, and a faulty computer or programming error.
Because the fault comes and goes, a quick meter check can miss it. Use a meter with MIN/MAX capture, a scan tool graph or a scope while you sweep the throttle slowly and wiggle the harness. If the sensor was replaced and P0124 persists, check its adjustment against your service manual.
First checks for any TPS code
Write down every code and the freeze frame
Other codes (pedal sensor, reference voltage, MAP or MAF) change the diagnosis. Fix those first if they point to a shared circuit.
Check for service bulletins
OBD-Codes.com puts this first for several of these codes. Makers publish known fixes for common faults.
Inspect the connector and harness
Look for corrosion, water, bent or pushed-back pins, and chafed wires near the throttle body.
Test reference, ground and signal
About 5 V on the reference, near zero on the ground, and a smooth sweep on the signal. See the test guide.
Replace only what failed
Sensor, wiring repair or throttle body. Then clear codes and run any relearn.
Full steps: how to test a TPS sensor. Not sure it is the sensor? Try the symptom checker.
OBD2 scan tools with live data
Questions people ask
What does sensor A mean in a TPS code?
Many throttles have more than one position signal. Sensor A is the first, B the second. On a cable throttle with one sensor, A is simply that sensor. On electronic throttles, A and B are the two signals the computer compares.
Can I clear a TPS code and keep driving?
Clearing it erases the evidence, not the fault. OBD-Codes.com suggests clearing a P0123 with no symptoms to see if it comes back, which is a fair test, but if the car hesitates, surges or loses power, find the cause first.
Are TPS codes the same on every car?
The generic code numbers and titles are shared across OBD-II vehicles, but makers word them differently, set them at different thresholds, and add their own related codes. Your service manual has the exact conditions.
Sources
Last reviewed 2026-10-12. General guidance only: specs, procedures and fitment vary by vehicle, so confirm in your service manual and on the listing before you buy or wrench.