How to Bypass TCC Solenoid

If you have a vehicle with an automatic transmission, you may have heard of the TCC solenoid. The TCC solenoid stands for transmission torque converter clutch solenoid, and it is responsible for controlling the fluid pressure that applies and releases the torque converter lockup clutch.

The torque converter lockup clutch is a mechanism that connects the engine and the transmission to achieve a 1:1 ratio of engine speed and transmission input speed, which improves fuel efficiency and reduces heat generation at high speeds.

Sometimes the TCC solenoid may malfunction, causing problems such as engine stalling, transmission slipping, poor gas mileage, or check engine light. In this blog post, we will show you how to bypass TCC solenoid using a simple method that involves a standard 194 light bulb. This method can help you diagnose and fix the problem without replacing the solenoid.

Why is the TCC Solenoid Important?

Why is the TCC Solenoid Important

The TCC solenoid is important because it helps optimize the performance and efficiency of your vehicle. By locking and unlocking the torque converter clutch at appropriate times, it reduces slippage, fuel consumption, and transmission temperature. It also prevents damage to the transmission components and prolongs their lifespan.

However, like any other electrical or mechanical part, the TCC solenoid can fail due to wear and tear, corrosion, dirt, or wiring issues. A faulty TCC solenoid can cause various problems, such as:

  • Stalling: If the TCC solenoid fails to disengage the clutch when the vehicle comes to a stop, the engine will stall because it cannot idle with the transmission locked.
  • Shuddering: The TCC solenoid fails to engage or disengage the clutch smoothly, you may feel a shudder or vibration when accelerating or decelerating.
  • Slipping: If the TCC solenoid fails to apply enough pressure to lock the clutch securely, you may experience slipping or loss of power when driving at higher speeds.
  • Overheating: TCC solenoid fails to lock the clutch when needed, you may notice an increase in transmission temperature due to excessive slippage and friction.
  • Check engine light: If the ECM or TCM detects a problem with the TCC solenoid circuit, it will store a diagnostic trouble code (DTC) and illuminate the check engine light on your dashboard.

How to Test the TCC Solenoid?

If you suspect that your TCC solenoid is not working properly, you can test it using a few simple tools and methods. Here are some steps you can follow:

  1. Check for DTCs: The first thing you should do is scan your vehicle for any DTCs related to the TCC solenoid using an OBD2 scanner. Some common codes are P0740 (TCC Solenoid Circuit Malfunction), P0741 (TCC Solenoid Circuit Performance or Stuck Off), P0742 (TCC Solenoid Circuit Stuck On), and P0743 (TCC Solenoid Circuit Electrical). If you find any of these codes, it means that there is an issue with the electrical or mechanical operation of the TCC solenoid.
  2. Check for voltage: The next thing you should do is check for voltage at the TCC solenoid connector using a multimeter or a test light. To do this, you need to locate and disconnect the TCC solenoid connector from the transmission valve body. You can find it under your vehicle, usually on the side of the transmission case. Consult your vehicle’s service manual for more details. Then, turn on your ignition and probe one of the terminals on the connector with your multimeter or test light. You should see 12 volts or a light on your tester. If not, there may be a problem with your wiring harness, fuse, relay, or ECM/TCM.
  3. Check for resistance: The last thing you should do is check for resistance at the TCC solenoid itself using an ohmmeter. To do this, you need to remove the TCC solenoid from the transmission valve body. You may need to remove some bolts, clips, or covers to access it. Consult your vehicle’s service manual for more details. Then, measure the resistance between the two terminals on the solenoid using your ohmmeter. You should see a reading between 10 and 40 ohms, depending on your vehicle model. If the reading is too high or too low, it means that the solenoid is faulty and needs to be replaced.

How to Bypass TCC Solenoid?

How to Bypass TCC Solenoid Guides

If you have confirmed that your TCC solenoid is bad and you want to bypass it temporarily until you can fix it, there is a simple trick you can use. All you need is a standard 194 light bulb and some wires. Here is how to bypass TCC solenoid:

What you will need

To bypass the TCC solenoid, you will need the following tools and materials:

  • A standard 194 light bulb
  • A wire stripper
  • A pair of pliers
  • Some electrical tape
  • A socket wrench
  • A jack and jack stands
  • A service manual for your vehicle

Step 1: Locate the TCC solenoid

The first step is to locate the TCC solenoid on your vehicle. The TCC solenoid is usually located on the transmission valve body, which can be found under the vehicle. Consult your service manual for the exact location of the TCC solenoid in your vehicle. You may need to remove some covers or panels to access it.

Step 2: Disconnect the TCC solenoid electrical connector

Using a socket wrench, remove the electrical connector from the TCC solenoid. The connector should have two wires: one for power and one for ground. You will need to identify which wire is which by using a test light or a multimeter. The power wire should have 12 volts when the ignition is on, and the ground wire should have continuity to the chassis.

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Step 3: Connect the light bulb to the power wire

Take the standard 194 light bulb and strip about half an inch of insulation from both ends of its wires. Then, use a pair of pliers to twist one end of the light bulb wire with the power wire from the TCC solenoid connector. Wrap some electrical tape around the connection to secure it.

Step 4: Connect the light bulb to ignition B+

The other end of the light bulb wire needs to be connected to ignition B+, which is a power source that is only active when the ignition is on. You can find ignition B+ in various places in your vehicle, such as the fuse box, the cigarette lighter socket, or the radio harness.

Use a test light or a multimeter to find a suitable ignition B+ source, and then strip some insulation from it. Twist the other end of the light bulb wire with the ignition B+ wire, and wrap some electrical tape around it.

Step 5: Test the transmission

You have successfully bypassed the TCC solenoid using a light bulb. The light bulb will serve as a load between ignition B+ and the TCC solenoid, simulating its function.

To test if this works, you will need to raise your vehicle on a jack and jack stands, and then start the engine. Put the transmission in drive mode, and then increase the engine speed to about 1500 RPM. The light bulb should light up, indicating that the torque converter lockup clutch is engaged.

If you press the brake pedal, the light bulb should turn off, indicating that the torque converter lockup clutch is disengaged. If this happens, then you have successfully bypassed the TCC solenoid.

Step 6: Replace the TCC solenoid

Bypassing the TCC solenoid using a light bulb is only a temporary solution that can help you diagnose and fix the problem. It is not recommended to drive your vehicle with this setup for a long time, as it may cause damage to other components or affect your vehicle’s performance.

Therefore, you should replace the faulty TCC solenoid as soon as possible with a new one. To do this, you will need to follow your service manual’s instructions on how to remove and install a new TCC solenoid.


The TCC solenoid is an important component of your transmission that helps improve your fuel economy and performance. If it fails, it can cause various problems such as stalling, shuddering, slipping, overheating, and check engine light. To diagnose and test your TCC solenoid, you can use an OBD2 scanner, a multimeter, a test light, and an ohmmeter. To bypass your TCC solenoid temporarily, you can use a standard 194 light bulb and some wires.

We hope this blog post (how to bypass TCC solenoid) has been helpful and informative for you. If you have any questions or comments, please feel free to leave them below. And if you need professional help with your transmission repair or replacement, contact us today for a free quote.

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