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Home / Codes / P2123
DTC code page

P2123: Throttle/Pedal Position Sensor/Switch D Circuit High Input

Quick answer: The ECU sees the pedal-position D circuit reading higher than expected, making accelerator input implausible.

Drivers also search this fault as pedal position sensor high input, APP sensor D high, P2123 reduced power.

Severity: high Family: powertrain Related paths: 9
Meaning

What P2123 usually means

P2123 is the high-input version of P2122 and belongs to the same accelerator-pedal trust problem. Instead of the signal being dragged low, the control module sees it biased high or otherwise out of expected range. A short to voltage, failing pedal sensor, reference issue, or connector damage can all create it. This page is worth adding because users frequently search pedal high-input faults when the vehicle drops into limp mode right after startup or throttle application, and it strengthens the APP side of the reduced-power graph.

Fast triage

Start here before chasing parts

  • Scan first: save freeze-frame and pending codes before clearing anything.
  • Confirm the complaint: compare the stored code with current drivability symptoms.
  • Use context: trims, live data, and related codes usually narrow the fault faster than guesswork.
  • Work simplest to hardest: leaks, connectors, maintenance items, and known patterns before expensive components.
Initial checks

What to check first

  • Look for companion P2122, P2128, or P2138 codes that show the broader pedal-correlation picture.
  • Inspect the APP connector and nearby harness for chafing or recent work.
  • Check whether the fault appears at key-on, tip-in, or after warmup.
Driving risk

Can you keep driving?

P2123 can force reduced-power mode because the ECU cannot safely trust accelerator demand when one pedal signal is too high.

High urgency: If symptoms are active, reduce driving and diagnose quickly before secondary damage builds.
Likely causes

Common causes behind this code

  • Pedal signal circuit is shorted to voltage
  • Internal pedal sensor fault is biasing the D circuit high
  • Reference or ground problem is distorting the signal upward
  • Connector damage or poor pin tension is causing an irrational high reading
  • Recent electrical work disturbed the APP harness

Cause phrases often tied to this code: short to voltage, pedal sensor fault, reference issue, connector damage, wiring problem.

Diagnostic order

Suggested workflow

  1. Save freeze-frame and observe the pedal signals live.
  2. Inspect wiring for short-to-power conditions or connector damage.
  3. Verify reference voltage and ground stability at the pedal assembly.
  4. Compare the suspect channel against the other APP channels through smooth pedal travel.
  5. Replace the pedal assembly if the high signal remains with confirmed good wiring.
Avoid guesswork

Common mistakes

  • Replacing the throttle body before checking the APP signals.
  • Treating a high-input pedal code as if it must be a software glitch.
  • Ignoring intermittent harness issues that only show up during pedal movement.
Repair path

Practical fix guidance

  • Fix wiring and supply faults before replacing the pedal.
  • Replace the pedal assembly when the high signal is internal to the sensor track.
  • Verify smooth pedal data and restored acceleration afterward.
Vehicle context

Affected brands in this MVP

Brand hubs help broaden internal linking now and can evolve into make-specific diagnostic notes later.

Aliases and common searches

English phrases tied to P2123

Useful when the driver knows the wording but not the exact DTC yet.

  • pedal position sensor high input
  • APP sensor D high
  • P2123 reduced power
Related search intent

Queries this page can answer naturally

  • P2123 code meaning
  • what does P2123 mean
  • throttle pedal position sensor switch D circuit high input
FAQ

Quick questions about P2123

What is the difference between P2122 and P2123?

P2122 is a low-input pedal signal fault, while P2123 is a high-input version of the same branch.

Can wiring cause P2123 without a bad pedal?

Yes. A short to voltage or connector problem can bias the signal high.

Why does P2123 sometimes appear right at startup?

Because the ECU checks APP signal plausibility as soon as it begins evaluating throttle control.