Toggle Side Panel

Shopping Cart

No products in the basket.

Shopping Cart

No products in the basket.

Close search
Home / DTC / P1878 — Gearbox potentio.#2 error(SIG.2)

P1878 — Gearbox potentio.#2 error(SIG.2)

Detailed page for trouble code P1878.

35,529codes
59brands
11,925generic
23,604specific
All codes P-codes (Powertrain) B-codes (Body) C-codes (Chassis) U-codes (Network/User) Tesla Alerts
Reset
Code

P1878

MITSUBISHI P — Powertrain

Gearbox potentio.#2 error(SIG.2)

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

Causes

  • Open or shorted signal wire between potentiometer #2 and TCM
  • Corroded/damaged connector or pin at potentiometer or TCM
  • Failed gearbox potentiometer (internal wear or contamination)
  • Water intrusion or corrosion at sensor/harness
  • Poor ground or missing reference voltage from TCM
  • Intermittent wiring harness chafe or connector contact problem

Symptoms

  • MIL (Check Engine/AT) illuminated
  • Transmission may go into limp/reduced-gear mode
  • Incorrect or erratic gear indication or inability to select some gears
  • Harsh or improper shifting
  • Intermittent operation that may change with vibration or lever movement

What to check

  • Read and record freeze-frame data and all transmission-related codes with a scan tool
  • Visually inspect potentiometer connector and harness for corrosion, bent pins, damaged insulation, or signs of water entry
  • Check for related codes (transmission range, speed sensors) to narrow fault
  • Clear the code and road-test to see if it returns and under what conditions
  • Wiggle harness/connector and observe for code reappearance or signal change

Signal parameters

  • Reference supply: typically a regulated reference from TCM (~5 V) — verify with service data
  • Signal output: potentiometer should vary smoothly within ~0.5–4.5 V as selector/gear position changes (varies by model)
  • Signal ground: good low-resistance ground connection required
  • No PWM frequency expected — output is an analog voltage that changes with position
  • If the output is open (OL/infinite) or shorted to battery or ground, the TCM will set the code

Diagnostic algorithm

  1. Verify battery voltage is stable (12 V); record stored/transmission codes and freeze-frame data.
  2. Perform visual inspection of gearbox potentiometer #2 connector and harness; repair obvious damage or corrosion.
  3. Backprobe the potentiometer connector: verify reference voltage (≈5 V), sensor ground continuity to chassis/TCM ground, and measure signal voltage while moving gear selector or rotating transmission selector linkage. Signal should change smoothly without drops to 0 V or jumps to battery voltage.
  4. If reference or ground missing, trace wiring back to TCM and repair open/shorts; check connectors at TCM.
  5. If wiring and reference/ground are good but signal does not vary or is out of range, remove potentiometer and measure its resistance and continuity per service spec; inspect for contamination or mechanical binding.
  6. Repair or replace damaged wiring/connector. If sensor is faulty, replace potentiometer/gearbox position sensor and re-test.
  7. After repairs, clear codes and perform functional test/road test to confirm code does not return. If fault persists, consider TCM diagnosis or replacement as last resort.

Likely causes

  • Corroded/loose connector at the gearbox potentiometer
  • Broken or chafed signal wire in harness near transmission body
  • Failed potentiometer (wiper wear or internal short)
  • Contaminated or water-damaged sensor connector

Fault status

⚠️ Status
Gearbox potentiometer #2 — signal circuit malfunction (open/short/out-of-range/intermittent)
🟡 Repair difficulty: Medium
⏱️ Diagnostic time: 0.5-2.0 hours

Similar codes

P0705 P0706 P0709 P0730 P0720
406

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

MITSUBISHI

Your experience will help others
+100 karma for a short comment :)
Keep it short and practical. Up to 500 characters.
Send to email

Report

Harassment or bullying behavior
Contains mature or sensitive content
Contains misleading or false information
Contains abusive or derogatory content
Contains spam, fake content or potential malware

Block Member?

Please confirm you want to block this member.

You will no longer be able to:

  • See blocked member's posts
  • Mention this member in posts
  • Invite this member to groups
  • Message this member
  • Add this member as a connection

Please note: This action will also remove this member from your connections and send a report to the site admin. Please allow a few minutes for this process to complete.

Report

You have already reported this .