How to Discharge a Capacitor to Reset Code

A vehicle's on-board computer monitors the engine's operating condition and adjusts settings to optimally run the engine. Sensors monitor various engine parts, including the fuel system, exhaust system and pressure of various components. When the sensors report failures, engine codes are stored in the on-board computer for retrieval by technicians for vehicle diagnosis. The code remains in the system until cleared, or until a sufficient amount of engine run time has passed. Clear codes by discharging the capacitors powering the short- and long-term memory in the on-board computer.

Instructions

Short-Term Memory Clearing

1

Turn off the vehicle.

2

Open the hood. Disconnect the negative cable from the battery terminal. The negative cable is black. Swing the cable away from the negative terminal, but do not allow it to touch any metal.

3

Wait three to five minutes to allow the short-term capacitor to discharge.

4

Reconnect the cable. Check the on-board computer to determine if the engine codes have been removed. If the engine codes are still present, they have been stored in long-term memory.

Clear Long-Term Memory

5

Open the hood. Remove both the red and black cables from the battery.

6

Insert the ignition key and turn it to the "electronics only mode." Press the horn and depress the brake pedal for approximately 30 seconds. The remaining power in the electrical system, including the capacitors powering the on-board computer's long-term storage, will be discharged.

7

Leave the battery cables disconnected for an additional 15 minutes to ensure that all residual electricity is discharged from the system.

8

Reconnect the battery cables.