OBD Guide
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P1790

Lock-Up Clutch Not Engaging

P1790 is an OBD-II diagnostic trouble code meaning: Lock-Up Clutch Not Engaging. Common causes: torque converter malfunction, lockout solenoid problems. Estimated repair cost: $33–167.

Severity
⚠️ Medium
Can you drive?
Yes, but get it checked soon
Approx. repair cost
$33–167 (est.)

Symptoms

  • Increased fuel consumption
  • Reduced acceleration dynamics
  • Transmission fluid overheating
  • Vibration when driving at constant speed
  • Rough idling

Causes

  • Torque converter malfunction
  • Lockout Solenoid Problems
  • Contaminated or low transmission fluid level
  • Malfunction of the blocking valve in the valve body
  • Problems with wiring or transmission ECU

How to Fix

  1. Check the level and condition of the transmission fluid
  2. Diagnose the operation of the locking solenoid
  3. Check the pressure in the transmission control system
  4. Perform hydraulic unit diagnostics
  5. If necessary, replace the torque converter

Related codes

P1791P1792

Error P1790 by Vehicle Brand

AcuraBuickCadillacChevroletGMGMCHondaInfinitiJaguarMazdaNissanOldsmobileSaturnVolkswagen

FAQ

What does the P1790 code mean?

P1790 is an OBD-II diagnostic trouble code that indicates: Lock-Up Clutch Not Engaging

What causes a P1790 error code?

The most common causes of P1790 include: Torque converter malfunction; Lockout Solenoid Problems; Contaminated or low transmission fluid level; Malfunction of the blocking valve in the valve body.

How do I fix a P1790 diagnostic trouble code?

To fix P1790: Check the level and condition of the transmission fluid. Diagnose the operation of the locking solenoid. Check the pressure in the transmission control system. For a complete diagnosis, use an OBD-II scanner.

Is it safe to drive with P1790?

Yes, but get it checked soon

How much does it cost to fix P1790?

The estimated repair cost for P1790 is $33–167. Actual cost depends on your vehicle, location, and labor rates.

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