Fuel & air metering · Powertrain · generic (SAE-defined)

P0123: Throttle/Pedal Position Sensor/Switch "A" Circuit High

P0123 means the "A" throttle or pedal position sensor signal voltage is higher than the engine computer considers possible for the current throttle position.

Severity: High — limit driving

Can I drive with P0123? Avoid driving except to get it repaired. A falsely high throttle reading can cause high idle or surging, and most electronic throttle systems will cut power as a safeguard.

Standard title per SAE J2012 / ISO 15031-6 · Updated 2026-11-07 · By CarWhere Research

How P0123 sets

The powertrain control module (PCM) monitors the "A" throttle position sensor (TPS) or pedal position sensor and expects its voltage to stay within a set range. If the signal rises above the highest plausible value for a set time, P0123 sets. Common causes include a signal wire shorted to voltage, an open ground and a failed sensor. Limits vary by manufacturer.

Common causes of P0123

Roughly most likely first; the actual cause depends on the vehicle and needs testing to confirm.

Open sensor ground circuit
Signal wire shorted to reference or battery voltage
Failed throttle position or pedal position sensor
Corroded or damaged connector
Faulty electronic throttle body assembly
PCM fault (rare)

P0123 symptoms

Check engine light on
Reduced power or limp mode
High or surging idle
Hesitation or erratic acceleration
Electronic throttle control warning light on some vehicles

How P0123 is diagnosed

Scan for codes and freeze frame data
Inspect the throttle body and pedal sensor wiring and connectors
Check the sensor ground for an open or high resistance
Check the signal wire for a short to voltage
Watch the signal in live data at closed and wide-open throttle
Replace the sensor or throttle body if wiring is good, then relearn

Typical fixes for P0123

Repair the open ground
Repair a wire shorted to voltage
Replace the throttle position sensor
Replace the electronic throttle body
Perform the throttle relearn procedure

Replace parts only after testing confirms the cause — a code names the circuit or condition that failed a check, not necessarily the faulty part. We don’t publish per-repair prices; for what households actually spend on upkeep, see car repair costs.

Manufacturer notes

Older definitions read "Throttle/Pedal Position Sensor/Switch A Circuit High Input". Definitions can vary by manufacturer; check factory service information.

Related codes & warning lights

P0120 P0121 P0122 P0223 P2135 P0507

P0123 FAQ

What does code P0123 mean?

P0123 means the "A" throttle or pedal position sensor signal voltage is higher than the engine computer considers possible for the current throttle position. The standard definition is "Throttle/Pedal Position Sensor/Switch "A" Circuit High."

Can I drive with a P0123 code?

Avoid driving except to get it repaired. A falsely high throttle reading can cause high idle or surging, and most electronic throttle systems will cut power as a safeguard.

Can P0123 cause a high idle?

Yes. If the PCM believes the throttle is more open than it is, idle speed control and fueling can be thrown off.

Is P0123 usually the sensor itself?

It is often the sensor or throttle body, but an open ground is also common, so check wiring before replacing parts.

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Sources

SAE J2012 — Diagnostic Trouble Code Definitions (standard code titles)
ISO 15031-6 — Road vehicles: communication between vehicle and external equipment for emissions-related diagnostics, Part 6: Diagnostic trouble code definitions
U.S. EPA — Vehicle Emissions Inspection and Maintenance (I/M) programs
U.S. EPA, 40 CFR 86.1806-17 — Federal onboard diagnostics requirements for light-duty vehicles
California Air Resources Board — On-Board Diagnostic (OBD) Program

General information written by CarWhere Research, not a diagnosis of your vehicle. Manufacturers can add their own sub-definitions and test conditions; confirm with the factory service information for your year, make and model. Before paying for a repair, check NHTSA for open recalls and your warranty booklet: federal law requires an emissions warranty on major emission-control parts such as the catalytic converter and engine computer.