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Home / DTC / P1237 — APS plausibility

P1237 — APS plausibility

Detailed page for trouble code P1237.

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P1237

MITSUBISHI P — Powertrain

APS plausibility

Brand: MITSUBISHI
Type: P — Powertrain
AI status
Completed
ready
Completed 100%
Page language: EN

Causes

  • Faulty accelerator pedal position sensor (APS) — sensor A or B
  • Open/short in APS wiring or connectors
  • Poor electrical connection (corrosion, bent pins) at pedal or ECM connector
  • Incorrect sensor reference/ground (5V reference issue)
  • Mechanical binding or return-spring failure in pedal assembly
  • Intermittent contact in sensor potentiometer or Hall element

Symptoms

  • Check Engine Light (MIL) illuminated
  • Reduced or limited engine power / limp-home mode possible
  • Unresponsive or jerky throttle behavior
  • Stored throttle/APS-related trouble codes (may see related codes)
  • Possible engine stalls or poor idle control in severe cases

What to check

  • Read and record freeze-frame and all stored DTCs with a scan tool
  • Inspect APS connector and wiring for damage, corrosion, pin fit, or chafing at the pedal harness
  • Visually inspect pedal assembly for binding, foreign objects, or broken return spring
  • With key ON (engine OFF) monitor live APS sensor values (both channels) on scan tool while slowly moving pedal — look for smooth correlated change
  • Measure sensor 5V reference and ground at connector with multimeter (key ON)
  • Check for intermittent faults by gently wiggling harness while monitoring live data or continuity

Signal parameters

  • APS typically uses a 5 V reference, ground, and two independent signal outputs (Sensor A and B)
  • Signal voltages normally vary smoothly across pedal travel (approx. 0.5–4.5 V range depending on design)
  • Both sensor outputs should track each other; expected correlation ratio varies by design — large divergence or inverted signals indicates implausibility
  • A sudden drop to 0 V or open-circuit reading, or stuck/high voltage near 5 V, indicates wiring or sensor failure

Diagnostic algorithm

  1. Connect a capable scan tool, read DTCs and freeze-frame data; note conditions when code set.
  2. Visually inspect pedal assembly, connectors, and wiring harness for damage, corrosion, or pin issues; repair any obvious faults.
  3. With ignition ON (engine OFF) monitor live data: slowly press and release pedal; both APS channels should change smoothly and remain correlated. Document voltages at rest and full travel.
  4. With multimeter measure 5V reference and ground at sensor connector to confirm stable supply and proper ground.
  5. Check for opens/shorts: verify continuity between sensor pins and ECM pins, and check for shorts to battery or ground if voltages abnormal.
  6. If wiring and supply are good but signals do not correlate, replace the accelerator pedal assembly (or APS).
  7. After repair, clear codes and perform functional test/road test; re-scan and confirm code does not return. If replacement does not cure, consider ECU input circuit testing or ECU replacement as a last resort.

Likely causes

  • Damaged or contaminated pedal connector or wiring harness
  • Faulty dual-output APS where the two sensor channels no longer correlate
  • Frayed wiring at pedal harness where it flexes with pedal movement
  • Poor 5V reference or ground at sensor

Fault status

⚠️ Status
APS plausibility — accelerator pedal position sensor signals are not correlating or are outside expected parameters.
🟡 Repair difficulty: Medium
⏱️ Diagnostic time: 0.5-2 hours

Similar codes

P0120 P0220 P0221 P2135 P2138
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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