P0123 code: Throttle/Pedal Position Sensor A Circuit High
P0123 means throttle/Pedal Position Sensor A Circuit High. The code says where to look, not what failed — the fix depends on which cause your car actually has.
What P0123 means
P0123 is the mirror of P0122: the throttle position sensor (TPS) is reading too HIGH (as if the throttle were wide open) or its circuit is shorted to voltage. The TPS tells the computer the throttle angle for fueling and, on drive-by-wire cars, throttle control. Common causes are a failed sensor, a wire shorted to power, or a corroded connector. On modern electronic throttle bodies the sensor is integrated, so the fix may be the whole unit. A faulty throttle signal can trigger reduced-power "limp" mode for safety.
P0123 symptoms
- Hesitation, surging, or erratic throttle response
- Reduced-power or "limp" mode
- High or unstable idle
- Harsh or unexpected automatic shifts
- Check-engine light, sometimes with a warning light
What it costs to fix P0123
Typical range: $50–$500 · about ~0.3–1.5 hrs of labor
| If the cause is… | Part | Labor |
|---|---|---|
| Throttle position sensor (standalone) | $20–$100 | ~0.3–0.8 hrs |
| Electronic throttle body (integrated TPS) | $150–$500 | ~0.5–1.5 hrs |
| Wiring / connector repair | $10–$120 | ~0.5–1.5 hrs |
Same as P0122: cheap on older cars with a bolt-on sensor, more on newer drive-by-wire cars where it means the throttle body. Wiring/connector repairs are inexpensive once located.
The price swings on which cause it turns out to be — so confirm the cause before paying. Diagnose P0123 for my exact vehicle →
How to fix P0123
Moderate — doable at home with common tools and patience
- Look for a short to voltage
A pegged-high signal usually means the signal wire is contacting a power feed, so inspect the harness for chafed insulation where the TPS wiring crosses other circuits, and check for aftermarket wiring taps near the throttle body. This failure mode is the mirror image of P0122 and is just as often a wiring fix.
- Examine the connector for water and corrosion
Moisture bridging pins inside the connector can feed reference voltage into the signal pin. Unplug it, dry it out, clean any corrosion, and reseat it firmly — then see if the reading returns to normal.
- Watch the signal through a throttle sweep
On a scan tool or with a back-probed meter, open the throttle slowly and watch TPS voltage. A reading stuck at or near reference voltage regardless of throttle angle means the sensor track or its wiring has failed high; a smooth sweep means the fault is intermittent and needs a wiggle test to provoke.
- Isolate sensor versus wiring
Unplug the sensor with the key on: if the computer now sees the signal drop to zero, the wiring is fine and the sensor was feeding the high reading. If the signal stays high with the sensor disconnected, the short is in the harness.
- Fix what the test found
Repair the shorted wiring, or replace the sensor — a simple bolt-on part on cable-throttle engines, a complete throttle body on drive-by-wire ones, typically followed by a relearn. Clear the code and confirm normal throttle response with no limp mode.
DIY or shop? The isolation testing here is classic multimeter work that a careful home mechanic can absolutely handle, and the unplug-and-watch trick in step four splits sensor from wiring without any special equipment. Where it turns into a shop job is the same place P0122 does: drive-by-wire throttle bodies cost more, and some vehicles insist on a scan-tool relearn before they'll leave reduced-power mode. Wiring shorts hidden deep in a harness are also tedious enough that shop diagnostic time can be worth it.
Tools for the DIY steps: Digital multimeter · OBD2 scanner with live data · Basic hand tools · Electrical contact cleaner · Wiring repair supplies
Not sure which step applies to your car? Get the likely cause for your exact vehicle before buying anything for P0123.
Start a case with P0123 and your car. Redline weighs these causes against what your car shows, and names the check that would settle it before you buy parts.
Can I drive with P0123?
Redline can’t determine from a symptom or code alone whether your car is safe to drive.
P0123: common questions
Can I drive with P0123?
Not something to decide from the code alone. It can cause erratic throttle response or reduced-power mode, which is risky in traffic. Get it inspected promptly and don't put off the repair; if acceleration is erratic, have it towed.
What's the difference between P0122 and P0123?
They're the same sensor failing in opposite directions: P0122 reads too low (or shorted to ground), P0123 reads too high (or shorted to voltage). Diagnosis and repair are essentially the same.
Will P0123 cause limp mode?
It can. A throttle signal the computer can't trust often triggers a reduced-power fallback that limits acceleration until the sensor or throttle body is fixed. If acceleration is limited or unpredictable, have it towed rather than driven.
How much does it cost to fix P0123?
Inexpensive on cars with a standalone sensor; more on newer ones where it means a throttle body. A wiring or connector repair is cheap. Diagnosis determines which before buying parts.
Related trouble codes
Don’t have a scanner yet? A ~$25 Bluetooth adapter reads codes like P0123 from your phone. See our guide to the best OBD2 Bluetooth adapters. Run a repair shop? See Redline for shops.
Generic OBD-II reference. Manufacturer-specific behavior varies. Confirm with a scan tool and, for safety-related codes, a professional inspection. Cost ranges are reference ranges, not quotes.
Seeing P0123 on your car?
Every problem becomes a Case. Tell Redline what the car is doing: it shows what the evidence supports, what’s still missing, and what to check next, before you approve a repair.
“Inner pad ~1 mm. Outer pad 3 mm.”
Next: check the slide pins move freely before buying parts.