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Home / DTC / P1820 — Neutral switch 2

P1820 — Neutral switch 2

Detailed page for trouble code P1820.

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P1820

MITSUBISHI P — Powertrain

Neutral switch 2

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

Causes

  • Faulty neutral position switch (Neutral Switch 2)
  • Damaged, corroded or loose connector at the switch
  • Open or shorted wiring between switch and TCM/ECM
  • Poor ground or missing reference voltage to the switch
  • Misadjusted shift linkage or position sensor
  • Intermittent connector contact from moisture or vibration

Symptoms

  • MIL/Check Engine light illuminated
  • Transmission may not recognize Neutral/Park; possible no-start in gear behavior
  • Incorrect gear selection indication or inability to shift
  • Start/shift interlock problems (engine may crank only in Neutral/Park)
  • Intermittent failure that clears in other ignition cycles

What to check

  • Read stored DTC and freeze frame data with a scan tool; note operating conditions when code set
  • Check live data for neutral switch status and transmission range input while shifting lever to Neutral/Park
  • Visually inspect switch, connector and wiring for corrosion, damage or pinbacking
  • Back‑probe connector to verify reference voltage, signal voltage and ground
  • Perform continuity and resistance checks on wiring between switch and TCM/ECM
  • Wiggle test harness with scan tool monitoring for intermittent changes

Signal parameters

  • Signal type: binary position switch (on/off) — closed or open circuit
  • Typical reference voltage: approx. 5 V (consult service manual for exact value)
  • Expected signal voltage: near 0 V when pulled to ground (closed) or near reference voltage when open — confirm with factory spec
  • Continuity: near 0 Ω when switch closed; very high resistance/open when open — check with ohmmeter per manual

Diagnostic algorithm

  1. Retrieve DTC(s) and freeze frame. Confirm P1820 and note conditions (ignition on, engine running, gear lever position).
  2. Visually inspect the neutral switch, connector and harness for corrosion, loose terminals, chafing, or physical damage.
  3. With ignition ON (engine off) back‑probe the switch connector. Verify reference voltage, signal voltage and ground at the switch connector. Compare to service manual values.
  4. Manually operate the shift lever to Neutral/Park while monitoring the signal with a scan tool or voltmeter. Confirm the switch changes state consistently.
  5. If signal is incorrect or intermittent, disconnect connector and check continuity/resistance between switch terminals and the TCM/ECM connector pins. Repair any open/shorted wiring or poor connections.
  6. If wiring checks good, bench test or replace the neutral switch and retest. Adjust shift linkage if switch actuation timing is out of spec.
  7. After repairs, clear codes, perform a functional test/road test and verify the code does not return.
  8. If fault persists after wiring and switch replacement, consider TCM/ECM diagnosis per manufacturer procedures.

Likely causes

  • Connector corrosion or loose terminal at neutral switch
  • Broken or shorted harness wire to TCM/ECM
  • Failed neutral switch (internal contact failure)
  • Shift linkage out of adjustment preventing correct switch actuation

Fault status

⚠️ Status
Neutral Switch 2 circuit malfunction — no valid neutral/park signal detected from Neutral Switch 2 (electrical fault, open/short, or switch failure).
🟡 Repair difficulty: Medium
⏱️ Diagnostic time: 0.5-2.0 hours
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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