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Home / DTC / P1746 — CVT cooler bypass valve open

P1746 — CVT cooler bypass valve open

Detailed page for trouble code P1746.

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P1746

MITSUBISHI P — Powertrain

CVT cooler bypass valve open

Brand: MITSUBISHI
Type: P — Powertrain
Views: UK: 17 EN: 24 RU: 23
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Page language: EN

Causes

  • Stuck or failed CVT cooler bypass valve (mechanical sticking or internal failure)
  • Failed bypass valve solenoid or coil (open circuit or short)
  • Wiring harness damage, corroded connector, or poor electrical connection to the valve
  • Faulty valve control relay or fuse
  • Transmission control module (TCM) or engine ECU fault (incorrect command or false feedback)
  • Obstruction or pressure condition in cooler/lines forcing valve open

Symptoms

  • Transmission fluid temperature higher than normal (ATF hot)
  • Transmission warning/engine warning lamp may illuminate (TCM fault)
  • Reduced CVT performance, hesitation or limp mode in some cases
  • Unusual shifting behavior or belt/chain slippage symptoms
  • Noisy transmission if overheating continues
  • Possible fluid leaks at cooler/hoses if pressure abnormal

What to check

  • Read freeze frame data and full DTC list with a capable scan tool; note conditions when code set
  • Check live PIDs for bypass valve status, ATF temperature, and any related transmission solenoid commands
  • Inspect wiring harness and connector at the bypass valve for corrosion, damage, proper seating and water intrusion
  • Check transmission fluid level, condition (burnt smell, dark color) and for contamination
  • Visually inspect external cooler, hoses and fittings for kinks, blockages or collapsed lines
  • Check transmission-related fuses and relays

Signal parameters

  • Typical control voltage range: 0–12 V depending on command (varies by model)
  • Control signal may be duty-cycle PWM (0–100%); factory data needed for exact duty vs. position
  • Typical solenoid coil resistance (approximate): 5–30 Ω (refer to service data for exact spec)
  • Open-circuit indication: infinite/very high resistance; short: near 0 Ω
  • When commanded closed, expected reduced voltage/duty; when commanded open, expected increased duty/voltage (manufacturer-specific)

Diagnostic algorithm

  1. Retrieve and record DTC(s) and freeze frame; clear codes and perform key-on/engine-off re-scan to see if code returns.
  2. With scan tool, monitor bypass valve PID and ATF temperature while commanding the valve open/close (actuation test). Note if valve responds to commands.
  3. Visually inspect valve connector and harness for corrosion, bent pins, heat damage or water ingress. Repair any damage and re-test.
  4. Measure solenoid coil resistance at the connector (unplugged). Compare to factory spec. Replace valve if resistance out of spec or open/shorted.
  5. Back-probe valve connector and with the valve connected, command the valve open/close while measuring control voltage/duty cycle. Confirm control module is commanding correctly.
  6. If valve does not actuate but control signal is present, bench-test or apply fused 12 V/GND per service instructions to verify mechanical movement (observe safety precautions).
  7. Inspect cooler and lines for blockage or collapsed hose that could affect pressure and force the valve open; flush or replace as needed.
  8. Check related fuses/relays and TCM grounds. If wiring and valve test good but code persists, investigate TCM output stage and update/reflash TCM software if available.
  9. After repair, clear codes and conduct a full road test under load to confirm normal ATF temperature and no reoccurrence.
  10. If intermittent, inspect for heat/water cycles and connector corrosion that may change with temperature.

Likely causes

  • Valve stuck open due to internal contamination or corrosion
  • Open or high-resistance wiring/connector to bypass valve solenoid
  • Failed solenoid coil or internal short
  • Blown fuse or bad relay supplying valve circuit
  • TCM output fault or software error

Fault status

⚠️ Status
TCM detected CVT cooler bypass valve open condition. Cooling bypass active or circuit indicating open; may cause elevated transmission fluid temperature and reduced CVT cooling efficiency.
🟡 Repair difficulty: Medium
⏱️ Diagnostic time: 1.5 to 3.0 hours

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406

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