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Home / DTC / P2126 — APS(sub) range

P2126 — APS(sub) range

Detailed page for trouble code P2126.

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Code

P2126

MITSUBISHI P — Powertrain

APS(sub) range

Brand: MITSUBISHI
Type: P — Powertrain
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Page language: EN

Causes

  • Faulty accelerator pedal position (sub) sensor (internal failure)
  • Damaged, corroded or loose connector at the APS or harness
  • Open, short or high resistance in signal, reference or ground wiring
  • Poor or intermittent 5V reference from ECM
  • Short to battery or ground on sensor signal circuit
  • Debris, binding or mechanical wear in pedal assembly

Symptoms

  • Malfunction Indicator Lamp (MIL/Check Engine) illuminated
  • Reduced engine power / limp-home mode
  • Delayed, erratic or no throttle response from accelerator pedal
  • Stored related throttle/pedal correlation codes
  • Possible intermittent faults that change with pedal movement or wiring flex

What to check

  • Retrieve freeze frame and live data for APS sensor A and APS(sub) (B) using a scan tool; compare voltages/percentages and check for correlation
  • Visually inspect pedal sensor connector and wiring for damage, corrosion, water intrusion, or loose terminals
  • Wiggle test harness while monitoring live data to check for intermittent changes
  • Check for stored related codes (e.g., pedal/throttle correlation) and any ECU power/ground faults
  • Measure sensor supply (usually +5V) and ground at the connector with ignition ON
  • Measure APS(sub) signal voltage at rest and while moving pedal; compare with expected ranges and with primary APS

Signal parameters

  • Reference supply: typically +5V from ECM (verify exact spec for vehicle)
  • Signal range: approx. 0.2 V to 4.8 V across full pedal travel (varies by model) — should change smoothly with pedal movement
  • Both APS sensors should vary with pedal and show different offset/slopes but remain correlated
  • No sudden drops to 0V, not stuck at a fixed voltage, and no excessive noise or erratic spikes

Diagnostic algorithm

  1. Verify fault is current; clear codes and perform a test drive while monitoring APS A and APS(sub) live data to reproduce.
  2. Perform a detailed visual inspection of pedal assembly, connector, and wiring; repair any obvious damage or corrosion.
  3. With ignition on (engine off), backprob the pedal connector: confirm +5V reference and good ground. If reference absent or weak, suspect ECM power/ground or harness.
  4. Measure APS(sub) signal voltage at rest and during pedal travel. Compare to factory spec and to primary APS; note smoothness and correlation. If signal out of range or non‑linear, suspect sensor or wiring.
  5. Wiggle the harness and connectors while watching live data for intermittent faults. Repair broken wires or poor terminals.
  6. If wiring checks OK, remove and bench‑test or replace the accelerator pedal module/sensor assembly per service manual.
  7. After repair, clear codes and confirm normal live readings and restoration of throttle response. If fault returns and wiring/sensor are good, investigate ECM input circuit or reflash/replace ECM as directed by manufacturer diagnostics.
  8. Document repairs and recheck for related codes (throttle actuator faults) and drivability symptoms.

Likely causes

  • Wiring/connectors between pedal sensor and ECM (most common)
  • Failed APS(sub) sensor element inside pedal module
  • Bad ground or weak 5V reference from ECM
  • Contamination or mechanical binding of pedal assembly
  • Less likely: ECM input circuit fault

Fault status

⚠️ Status
P2126 — Accelerator Pedal Position (sub) sensor signal out of expected range or not correlating with primary APS. ECM logged fault and may have enacted limp mode or reduced throttle response.
🟡 Repair difficulty: Medium
⏱️ Diagnostic time: 0.5-2.5 hours

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406

Browse 406 MITSUBISHI manuals: repair procedures, diagnostics, wiring diagrams, component locations, service data and Labor Times by year, model and trim.

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