Subaru Throttle Body Relearn

Subaru Throttle Body Relearn Procedure — idle relearn

If your Subaru stalls after a battery disconnect, here’s why it

Subaru electronic throttle body

happens and what you can do to fix it. Subarus since the mid 2000’s have an electronic throttle body. Over time those throttle bodies can develop carbon buildup. As the carbon builds up, the ECM learns a new “home” position for the throttle plate. However, when you disconnect the battery or clean the throttle body, you must perform a Subaru throttle body relearn. We call it a throttle body relearn, but Subaru calls it an idle relearn.

The ECM assumes you’ve cleaned the throttle body if you disconnect the battery. So you’ll most likely get a stall any time you disconnect the battery.

Subaru throttle body relearn procedure — step-by-step

1) Turn off all vehicle electrical accessories.
2) Disconnect the battery for 30 mins.
3) Reconnect the battery.
4) Turn the key to the ON position but do NOT START THE ENGINE. The ECM will force the throttle body to perform a wide open throttle and full closed throttle movement several times. Wait 20-seconds for the electronic throttle body to perform this procedure!
5) Start the engine but do not touch the gas pedal. Let it idle for 20-seconds.
6) You may notice the idle speed rise and fall. Do not touch the gas pedal!
7) Let the engine run for a full 10 mins but DO NOT TOUCH THE ACCELERATOR or turn on any electrical accessories. That would cause a draw on the alternator and change idle speed during the relearn process.
8) Turn off the engine. Leave it off for 20-seconds.
9) Turn the key to the ON position for 20-seconds without starting the engine or applying the gas pedal.
10) Start the engine and let it idle for a further 5 minutes without touching the accelerator and without turning on other systems in the car.
11) Turn off the engine again and wait at least 20 sec before restarting.
12) Take the car for a test drive as the ECU should now be fully retrained.

©, 2022 Rick Muscoplat