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How to Disconnect a Battery to Reset a Transmission

by Cassandra Tribe

Once a transmission repair is completed on a vehicle, the last step to carry out is to reset the "check engine" light and error codes recorded in the vehicle's computer memory. One option is to drive the vehicle to a shop and have the computer reset, using an OBD reader. The other option is to disconnect the vehicle's battery in order to reset any error codes, including a transmission error code. Disconnecting the battery and resetting the computer may be faster, but it may create potential problems.

Step 1

Open the hood of the car.

Step 2

Disconnect the negative cable from the battery, using a wrench to loosen the lug nut on the terminal and pulling the cable off the post. Pull the cable out of the way to eliminate any risk of the cable accidentally falling and touching the battery post.

Step 3

Disconnect the positive cable from the battery, using a wrench to loosen the lug nut on the terminal and pulling the cable off the post.

Step 4

Open the driver's side door, press and hold down the horn until the sound of the horn stops completely. This will discharge the stored charge in the engine's control module capacitor and clear any error code from the control module's memory.

Step 5

Reconnect the positive cable to the positive terminal of the battery and tighten the lock nut, using a wrench, until it is hand-tight.

Reconnect the negative battery cable to the negative terminal of the battery and tighten the lock nut, using a wrench, until it is hand-tight.

Tip

  • Alternately, leave the battery disconnected for at least a 1/2 hour to complete the discharge, if blowing the horn is not a choice action to perform.

Warning

  • Resetting the "check engine" light by disconnecting the battery can cause the radio to return to its factory settings. Make sure the security code is on hand to avoid being prevented from using it.

Items you will need

  • Wrench

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