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DTC codes / Nissan codes / P1550

P1550 · NissanTCC Solenoid Valve

P1550 on Nissan vehicles indicates that the torque converter clutch (TCC) solenoid valve circuit has an electrical fault, such as an open, short, or excessive resistance. The transmission control module (TCM) monitors the solenoid's electrical current and sets this code when the measured value falls outside the expected range, preventing proper lockup of the torque converter.

SystemPowertrain
Code typeNissan specific
SeverityMedium
Fix difficultyIntermediate
AreaVehicle speed, idle control and auxiliary inputs

Symptoms you may notice

  • Illumination of the check engine light or service engine soon light on the dashboard.
  • Often no symptoms besides the warning light, especially if the fault is intermittent.
  • Harsh or delayed transmission shifts, particularly when the torque converter attempts to lock up.
  • Reduced fuel economy due to the torque converter not locking up at cruising speeds.
  • Possible shudder or vibration during light acceleration or steady-speed driving.
  • In some cases, the transmission may enter limp mode or fail to engage overdrive.

Common causes, most likely first

  1. Faulty torque converter clutch solenoid valve (internal transmission failure).
  2. Damaged or corroded wiring harness or connector at the transmission solenoid pack.
  3. Open or short circuit in the TCC solenoid control circuit.
  4. Contaminated transmission fluid causing solenoid malfunction or sticking.
  5. Failed transmission control module (TCM) or valve body issues.
  6. Poor ground connection for the solenoid circuit.
  7. Aftermarket or incorrect transmission fluid causing electrical resistance changes.

How to diagnose and fix it

  1. Check transmission fluid level and condition; top off or replace if contaminated.
  2. Inspect the TCC solenoid connector and wiring for damage, corrosion, or loose pins.
  3. Measure the resistance of the TCC solenoid at the transmission connector and compare to factory specification.
  4. Test the solenoid control circuit for continuity and shorts to ground or power using a multimeter.
  5. If resistance is out of spec, replace the TCC solenoid valve (often part of the solenoid pack).
  6. Clear the code and perform a road test to verify the repair and ensure the code does not return.
  7. If the code persists, diagnose the TCM and valve body for internal faults.

TCC Solenoid Circuit Checks Before Replacement

  • A common misdiagnosis is replacing the TCC solenoid when the real problem is a chafed wire in the harness near the transmission mount or a corroded connector pin.
  • P1550 can be set by low or degraded transmission fluid that causes the solenoid to draw excessive current, so always check fluid condition before condemning the solenoid.
  • On some Nissan models, the TCC solenoid is part of the valve body assembly and cannot be replaced separately, requiring a more extensive repair.
  • Intermittent P1550 codes often occur due to heat-related resistance changes in the solenoid coil, which may only act up when the transmission is at operating temperature.
  • A faulty brake pedal switch or wiring can prevent torque converter lockup and set related codes, so verify brake switch operation if the TCC solenoid tests good.

Can I keep driving with P1550?

You can usually continue driving with P1550, but avoid heavy acceleration and towing until repaired, as the torque converter may not lock up properly, reducing fuel economy and potentially causing transmission overheating. If the vehicle enters limp mode or shifts harshly, seek service promptly.

Tools that help

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Guidance is general and written for Nissan vehicles. Exact tests and values vary by model, so confirm the fault before replacing parts.

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