How to Perform a Throttle Body Relearn on Kia Vehicles
If you own a Kia vehicle and have recently replaced the throttle body or disconnected the battery, you may need to perform a throttle body relearn procedure. This process recalibrates the electronic throttle control system so it can properly regulate the engine idle speed and throttle response. Failing to do a relearn can result in rough idling, stalling, poor acceleration, and check engine lights. In this comprehensive guide, we’ll cover everything you need to know about throttle relearning on Kia models, including which vehicles require it, when it’s necessary, and step-by-step instructions for carrying out the procedure using a scan tool. By the end, you’ll have the knowledge and confidence to complete a throttle body relearn yourself and restore optimal performance to your Kia.
What is a Throttle Body Relearn?
The throttle body is the part of your Kia’s air intake system that controls the amount of air flowing into the engine. It contains a valve that opens and closes to regulate airflow based on input from the gas pedal. In modern electronic throttle control (ETC) systems, the throttle valve is controlled by an electric motor rather than a cable. Over time, carbon buildup and wear can cause the throttle body to go out of alignment with the preset parameters in the engine control module (ECM). This can lead to incorrect airflow readings and improper throttle control. A throttle body relearn procedure recalibrates the ETC system by erasing the old adaptive values in the ECM and allowing it to relearn the correct throttle position.
When to Perform a Throttle Body Relearn
There are several situations when a throttle relearn is necessary on Kia vehicles:
- After replacing the throttle body
- After cleaning the throttle body
- After disconnecting or replacing the battery
- After an ECM reflash or update
- When diagnosing rough idle, stalling, or hesitation issues
Some common symptoms that indicate a throttle relearn may be needed include:
- Rough or unstable idle
- Stalling after starting the engine
- Hesitation or stumbling on acceleration
- Check engine light on with throttle-related trouble codes like P0121, P0122, P0123, P0222, P2135
If you notice any of these signs after servicing the throttle body or battery, it’s a good idea to do a relearn before driving the vehicle further.
Kia Models That Require Throttle Relearning
Most Kia models from 2011 and newer with electronic throttle control are equipped with Theta II, Nu, or Gamma engines that utilize drive-by-wire technology. This means there is no physical link between the accelerator pedal and throttle body. Instead, the throttle is controlled electronically by the ECM based on pedal position sensor input. While not an exhaustive list, here are some popular late model Kias that commonly require throttle body relearning:
- Kia Forte (2019-2023)
- Kia K5 / Optima (2011-2020)
- Kia Rio (2018-2023)
- Kia Seltos (2021-2023)
- Kia Sorento (2011-2023)
- Kia Soul (2012-2023)
- Kia Sportage (2011-2023)
- Kia Stinger (2018-2023)
- Kia Telluride (2020-2023)
If you have one of these vehicles or another Kia model with an electronic throttle body, it’s important to perform a relearn anytime the system is serviced or reset. Consult your owner’s manual or a repair database to confirm the procedure for your specific year and model.
Tools Needed for Throttle Relearn
To do a throttle body relearn on most Kia vehicles, you will need a scan tool capable of accessing the ETC and clearing adaptive values. While some high-end scan tools have built-in relearn functions, most affordable consumer-grade devices can get the job done as long as they support the following features:
- OBD2 compatibility with your Kia’s model year
- Ability to read and clear diagnostic trouble codes
- Bi-directional control to access ECM functions
- Option to reset adaptive values or perform ETC relearn
You’ll also need a safe, level place to park your vehicle while carrying out the relearn. Make sure the parking brake is engaged and the transmission is in Park or Neutral depending on your model.
Step-by-Step Throttle Relearn Instructions
Follow these steps to relearn the throttle body on your Kia:
- Connect your scan tool to the vehicle’s OBD2 port under the dashboard. Turn the key to the “On” position but do not start the engine.
- Allow the scan tool to boot up and establish communication with the ECM. Select your Kia model if prompted.
- Navigate to the “Codes” menu and check for any existing trouble codes related to the throttle system (e.g. P0121, P0122, P0123, P0222, P2135). Write down these codes if found.
- Clear all codes and reset the check engine light using the scan tool’s “Erase Codes” function. Clearing codes also resets adaptive values.
- Navigate to the “ETC” or “Throttle Body” menu on your scan tool. Look for an option to perform a throttle relearn, reset adaptive values, or recalibrate the throttle position sensor.
- Select the relearn option and follow the on-screen prompts. The scan tool will instruct you to turn the ignition off, wait a specified time (usually 10 seconds), then turn the key back to the “On” position without starting the engine.
- After turning the key to “On”, wait at least 5 seconds for the ECM to relearn the base throttle position. Do not press the accelerator pedal during this time. Some scan tools may display a countdown or confirmation message.
- Once the relearn is complete, start the engine and let it idle. Check for any roughness, hesitation, or stalling. The idle may be slightly high at first but should stabilize after a few seconds.
- With the engine running, check for any new trouble codes using the scan tool. Address any persistent throttle-related faults before clearing codes again.
- Road test the vehicle to confirm proper throttle response and power delivery. Vary your throttle inputs and speeds to help the ECM fully relearn the ETC adaptive values under different conditions.
If the relearn procedure doesn’t resolve your throttle issues, there may be an underlying problem with the throttle body, wiring harness, pedal position sensor, or ECM that requires further diagnosis. Consult the factory service information for your Kia model for detailed troubleshooting steps, wiring diagrams, and component tests.
Frequently Asked Questions
Q: Can I perform a throttle body relearn without a scan tool?
A: On some older Kia models, you can do a manual relearn by following a sequence of key cycles and throttle presses. However, most newer models require a scan tool to access the ECM and reset adaptive values. Attempting a manual relearn on the wrong vehicle can set incorrect values and cause further issues.
Q: How often should I perform a throttle body relearn?
A: A relearn should only be necessary after servicing the throttle body, disconnecting the battery, or updating the ECM. Some technicians recommend resetting adaptive values if the battery dies or is jump started. Cleaning the throttle body every 30,000 miles can help prevent the need for frequent relearns.
Q: What happens if I don’t perform a relearn after replacing the throttle body?
A: The ECM will continue to use the old adaptive values which no longer match the new throttle body’s parameters. This can cause incorrect air/fuel ratios, rough idle, hesitation, and trigger check engine lights. Always do a relearn after any throttle service.
Q: Can a dirty throttle body cause the need for a relearn?
A: Yes, carbon deposits on the throttle plate and bore can change the idle position enough to set codes and illuminate the check engine light. Cleaning the throttle body and performing a relearn can often resolve these issues without replacing parts.
Q: Why does my Kia stall or stumble after a throttle body relearn?
A: This can happen if the relearn process is interrupted or not completed properly. Make sure to follow the scan tool prompts carefully and wait the full specified time for the ECM to learn the new values. If stalling persists, check for vacuum leaks, clean the idle air control valve, and inspect the throttle body
for sticking.
fINAL Words from Boss Erwin
Performing a throttle body relearn is critical to maintaining proper engine operation on Kia vehicles equipped with electronic throttle control. By resetting the adaptive values after throttle service or ECM updates, you allow the system to recalibrate itself for optimal performance.