How long should battery be disconnected to reset ECU?

It's a real tight fit, but if you can find it and disconnect it, leave it disconnected for 30 seconds. The nice thing about this method over the "disconnect the negative cable" method is that you don't have to reprogram your radio! If you can't find it, then do the negative cable - again for about 30 seconds.

Regarding this, does disconnecting a car battery reset the ECU?

The car ECU maps aren't held in volatile memory, so will not be affected by removing the battery. if it did, then your cars ECUs would all reset to factory every time the battery was removed.

Beside above, how long does it take for a car computer to reset? How to Reset a Car Computer

Open up the hood.
Remove the positive terminal cable from the battery using your pliers or wrench.
Go to your fuse box in your car, and look at the diagram. Select the fuse that is labeled "ECM" and remove this fuse.
Keep the car disconnected like this for two to three minutes to clear the computer's memory.

Consequently, do I disconnect the positive or negative to reset ECU?

When removing cables, remove negative first, then positive. If you just want to reset the ECU, removing only negative is good enough. When installing cables, install positive first, then negative.

When should I reset my ECU?

ECU Reset

The ECU "learns" about your engine as you drive the car.
"Resetting the ECU" is the process of clearing all the long term memory from the ECU's memory.
To "reset" the ECU, all you have to do is remove the source of backup power.

How do I reset my ECU without disconnecting the battery?

Easy Way to Reset ECU without battery disconnect. 3) Wait 7 seconds then floor the gas pedal and hold for 10 seconds. After that 10 seconds the Check Engine Light will start to blink slowly. 4) Release the pedal and floor it down once again and hold for 10 seconds.

Does changing car battery affect ECU?

Disconnecting your car battery will not cause any permanent damage to your computer or ECU (electronic control unit), but it can have some adverse effects. Those include canceling your preset radio stations, forgetting learned shift points, and your car's ideal fuel/air mixture.

What happens if you unplug the ECU?

Well, unplugging the battery resets your clock and radio stations, which is a pain. First rule when doing anything to the ecu is to disconnect the battery. Just like any computer you need to unplug it before you work on it.

How do I reset my ECU 1500?

How to Reset the ECM on a Chevy Truck

Remove the nut from the negative battery cable using a socket set or wrench. Slide the cable off of the battery and set it aside.
Turn the headlight switch to the "On" position to drain the ECM of any remaining power. Wait at least 10 minutes, then turn it back to the "Off" position.

Does a used ECU need to be reprogrammed?

Yes. In fact, if you want to change the ECU for any reason, a dealer will have to reprogram your keys into the ECU. Or it will not start.

Does disconnecting the battery clear codes?

The battery disconnect method will work on most vehicles. Some late model vehicles will not clear trouble codes by disconnecting the battery. On these vehicles trouble codes are stored in the ECM's ROM, and only a scan tool will clear trouble code(s) and turn off the check engine or malfunction indicator lamp (MIL).

What does resetting an ECU do?

"Resetting the ECU" is the process of clearing all the long term memory from the ECU's memory. These variables trim idle speed, fuel, spark, and more. The ECU will also store trouble codes for diagnostic capability.

How long does an ECU last?

The engine control unit is a component that can last the lifetime of the vehicle, or develop issues after 100,000 miles.

Can I reset my car's computer?

You can use two methods for resetting your car's computer. The first option is to turn off the car's battery to break the circuit and erase all memory. On the other hand, you can go about the computer reset procedure with the car battery still on and attached to the car.

What happens if you disconnect the positive terminal first?

By removing the negative battery cable you are disconnecting the battery from the chassis of your vehicle. If you begin to remove the positive side before the negative and your wrench would make contact with any part of the vehicle, then you could cause a short in the system.

Does disconnecting battery reset car computer?

An old mechanic's trick for turning for temporarily eliminating certain kinds of driveability problems is to disconnect the battery ground cable for 10 seconds to "reset" the computer. Essentially, this trick erases the stored fault codes in the PCM's keep alive memory and turns the Check Engine light off.