P0742Generic code

P0742 Code: Torque Converter Clutch Circuit Stuck On

The P0742 code means the torque converter clutch solenoid in the automatic transmission behaves as if it is always on, or stuck on. It is usually caused by dirt in the fluid, degraded fluid or wear in the valve body.

Severity
High
Can I keep driving?
Yes, but with caution
Estimated cost
$80 to $900
Difficulty
Hard
System
Transmission
Applies to
All OBD2 vehicles

Updated Reviewed by Renzo Chacca

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What the P0742 code means

Solenoids are electric valves that direct fluid pressure to the clutches and brakes inside the transmission. The torque converter clutch solenoid locks the torque converter at cruising speed so the engine and transmission turn together without slipping, which cuts fuel use and heat. The transmission computer commands the solenoids and monitors both their electrical circuit and the result, meaning the input and output speeds of the transmission.

The P0742 code means the solenoid behaves as if it is always on, or stuck on. Electrically it may be fine, because the problem is hydraulic or mechanical. Wear particles in the fluid jam the solenoid valve or the passages in the valve body.

On any transmission code, the first check is the fluid. Check the level with the manufacturer procedure (often with the engine running and at a specific temperature). The fluid should be red or pink and should not smell burnt. Low or worn-out fluid causes slipping, harsh shifts and solenoid or ratio codes that go away once it is corrected.

This kind of fault usually does not show up with a multimeter, because electrically everything looks right. You have to compare what the part says with what actually happens, using a pressure gauge, a thermometer, a tachometer, or by commanding the component with the scan tool and watching whether the physical result matches the command.

Read the P0700 guide to understand how transmission codes are read and why you need a scan tool that can talk to the transmission module.

P0742 code symptoms

  • Check engine light on.
  • High rpm on the highway (the converter does not lock).
  • The engine stalls when you stop (converter stuck locked).
  • Vibration at cruising speed.
  • Higher fuel use.

Likely causes of the P0742 code

  1. Degraded fluid or fluid with particles. The most common cause of stuck solenoids.
  2. Wrong fluid level. Too low causes slipping, and too high causes foaming.
  3. Solenoid mechanically stuck by dirt.
  4. Valve body wear and internal pressure leaks.
  5. Worn internal clutches in transmissions with a lot of miles.

How to diagnose the P0742 code step by step

  1. Check the fluid level and condition using the manufacturer procedure.
  2. Read all the codes in the transmission module with a scan tool that can reach it.
  3. Measure the solenoid resistance at the transmission connector and compare it with the manual.
  4. Check the insulation to ground. It should read infinite.
  5. Command the solenoid with the scan tool and listen for the click.
  6. Inspect the case connector. Look for fluid inside it or green pins.
  7. Compare input and output speeds in each gear to see which gear slips.
  8. Run a line pressure test with a gauge if the transmission has a test port.

How to fix the P0742 code

  • Change the transmission fluid and filter using the specified fluid.
  • Clean or replace the solenoid or the valve body.
  • Clear the adaptations and perform the relearn procedure.
  • If the clutches are worn, the transmission needs a repair.

Technical reference data

  • Shift solenoids (on/off): roughly 10 to 30 ohms.
  • Pressure or linear solenoids (PWM control): roughly 3 to 8 ohms.
  • Normal transmission fluid temperature: 70 to 95 °C (158 to 203 °F).
  • Reference values: check the manufacturer data for your vehicle.

Brand-specific notes

On many transmissions the solenoids sit in the valve body and you reach them by removing the pan. On some, the solenoids are sold only together with the valve body or with the built-in control module (a mechatronic unit). After you replace solenoids or the valve body, clearing the adaptations and doing a relearn with a scan tool is usually required.

P0742 on Aisin and Jatco

On many Aisin and Jatco transmissions the solenoids are in the valve body and are reached by removing the pan.

P0742 on GM

On the GM 6T transmissions the solenoids are in the valve body and are reached by removing the pan.

P0742 on Ford

On the Ford 6R transmissions the solenoids are in the valve body and are reached by removing the pan.

P0742 on Volkswagen

The Volkswagen DSG uses a mechatronic unit, and on many modern transmissions the solenoids come only with the valve body or with the integrated control module.

Frequently asked questions about P0742

Can I drive with a P0742 code?
With caution and only as far as the shop. The transmission can drop into limp mode, and driving that way for a long time wears it out, so do not ignore a P0742 code.
Will a fluid change fix it?
Sometimes it does, especially for performance or stuck codes. For electrical faults it does not.
Does the transmission have to come out?
Normally not. The solenoids are replaced by removing the pan or the valve body cover.
How much does it cost to fix P0742?
Roughly $80 to $900, and more if the transmission itself needs repair.
What does the P0742 code mean?
It is a generic OBD2 code that means the torque converter clutch solenoid is stuck on. The converter locks when it should not, usually because of dirty or worn fluid, or a worn valve body.

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