Can P0123 cause unintended acceleration?

On older cable-throttle vehicles, a stuck-high TPS mostly causes ECM logic problems rather than actual physical acceleration. On drive-by-wire, the ECM typically detects sensor conflict and defaults to idle or limp mode rather than commanding wide-open throttle.

Why does the engine stall with P0123 if the sensor says throttle is wide open?

The ECM cuts fuel when it detects an implausible wide-open throttle signal at zero engine demand. It is a safety response to prevent uncontrolled acceleration.

Does P0123 affect the fuel trims?

Yes. A TPS stuck high makes the ECM think the engine needs maximum fuel all the time, driving fuel trims toward rich and causing misfires from flooding.

Codes › P0123

P0123: The throttle position sensor voltage is too high

Throttle/Pedal Position Sensor/Switch A Circuit High Input

Moderate severityCan you keep driving?

No. A TPS reading stuck at maximum makes the computer think the throttle is wide open. This can cause unexpected high RPM, dangerous surging, or the ECM may shut down fuel entirely as a safety measure. Do not drive.

What it means

P0123 means the TPS signal voltage is above the maximum the ECM expects. A sensor stuck high tells the computer the throttle is fully open even at idle. The ECM may cut fuel to prevent a runaway condition, or the engine may surge unexpectedly. The most common electrical cause is a short to the 5V reference line or an internally failed sensor with an open circuit that floats toward the supply voltage.

Common causes

Failed TPS sensor with internal open circuitAn open internal circuit floats the output toward 5V, which reads as wide-open throttle.
Short to 5V reference in the signal wireA chafed signal wire touching the reference wire holds the output high regardless of actual position.
Damaged connector bridging signal and reference pinsA melted or bent connector can allow the signal pin to contact the 5V pin.

What it costs

TPS replacement (cable)$80 to $250
Electronic throttle body$300 to $800
Wiring repair$100 to $300

Symptoms

Check engine light on
High idle or engine surging
Transmission shifting very aggressively or not at all
Engine may stall from fuel cutoff at idle
Possible runaway RPM if the ECM does not intervene

What to do next

Do not attempt to drive this vehicle. Disconnect the TPS connector and check whether signal voltage drops toward zero with the sensor unplugged. If it does, the sensor is shorted internally to its own reference. If voltage stays high with the sensor disconnected, the wiring has a short to the 5V supply line. Replace the sensor or repair the wiring accordingly.

Lewis shows live TPS voltage so you can immediately confirm whether the signal is pinned at maximum or only spiking high at certain throttle positions. Download Lewis.

Related codes

FAQ

Can P0123 cause unintended acceleration?: On older cable-throttle vehicles, a stuck-high TPS mostly causes ECM logic problems rather than actual physical acceleration. On drive-by-wire, the ECM typically detects sensor conflict and defaults to idle or limp mode rather than commanding wide-open throttle.
Why does the engine stall with P0123 if the sensor says throttle is wide open?: The ECM cuts fuel when it detects an implausible wide-open throttle signal at zero engine demand. It is a safety response to prevent uncontrolled acceleration.
Does P0123 affect the fuel trims?: Yes. A TPS stuck high makes the ECM think the engine needs maximum fuel all the time, driving fuel trims toward rich and causing misfires from flooding.