How to Perform a Throttle Relearn on Your Land Rover
If you own a Land Rover equipped with an electronic throttle control system, you may need to perform a throttle relearn procedure after cleaning the throttle body or if you experience rough idle, stalling, or poor throttle response. A throttle relearn, also known as an idle relearn, allows the vehicle’s engine control module (ECM) to relearn the closed and open positions of the throttle body after changes have been made.
What is a Throttle Body?
The throttle body is a key component of your Land Rover’s air intake system. It controls the amount of air flowing into the engine, which in turn affects engine speed, power output, and fuel efficiency. In modern vehicles like Land Rovers, the throttle body is electronically controlled by the ECM. Over time, carbon deposits can build up on the throttle body, affecting its performance. Cleaning the throttle body can help restore proper functioning, but the ECM will then need to relearn the throttle body’s position sensors.
Symptoms Indicating a Throttle Relearn is Needed
You may need to perform a throttle relearn on your Land Rover if you notice any of the following symptoms:
- Rough idle: The engine idles roughly, fluctuates, or stalls.
- Poor throttle response: Delayed or inconsistent acceleration when pressing the gas pedal.
- Check engine light: The malfunction indicator lamp (MIL) illuminates and throttle body-related error codes are stored, such as P2119 or P1639.
- Recent throttle body service: You recently cleaned the throttle body or replaced it with a new unit.
If you experience any of these issues, a throttle relearn procedure can help restore proper operation. However, it’s important to first diagnose the underlying cause and address any mechanical problems before performing the relearn.
Land Rover Models Requiring Throttle Relearn
The throttle relearn procedure applies to a wide range of Land Rover models equipped with electronic throttle control. While the exact steps may vary slightly between models and years, the general process is similar. Consult your owner’s manual or a Land Rover service professional for specific instructions for your vehicle. Some of the Land Rover models that commonly require a throttle relearn include:
- Range Rover (L322, L405)
- Range Rover Sport (L320, L494)
- LR3/Discovery 3 (L319)
- LR4/Discovery 4 (L319)
- Range Rover Evoque (L538)
- Discovery Sport (L550)
If you’re unsure whether your specific Land Rover model requires a throttle relearn or which procedure to follow, it’s best to consult with a qualified Land Rover mechanic or refer to the factory service manual for guidance.
Throttle Relearn Methods
There are a few different methods to perform a throttle relearn on a Land Rover, depending on the model and year. The two most common methods are:
- Pedal method: This involves pressing and holding the accelerator pedal in specific positions to initiate the relearn process.
- Diagnostic tool method: This utilizes a Land Rover-specific diagnostic tool, such as the IIDTool, to command the ECM to perform the relearn.
We’ll cover the details of each method in the following sections. Choose the method that applies to your specific vehicle.
Pedal Method Throttle Relearn
The pedal method is a simple way to perform a throttle relearn on many Land Rover models without needing a diagnostic tool. Here’s a general procedure that works for most models:
- Ignition on, engine off: Put the key in the ignition and turn it to the “ON” position (position II) without starting the engine. All the warning lights on the dash should illuminate.
- Depress accelerator pedal: Slowly press the accelerator pedal all the way down to the floor and hold it there.
- Wait: Keep the accelerator pedal fully depressed for at least 15-20 seconds. You may hear the throttle valve motor inside the throttle body operating during this time.
- Release pedal and turn off ignition: After holding the pedal down for the specified time, release it and turn the ignition off to position 0.
- Wait 2 minutes: Leave the ignition off for approximately 2 minutes to allow the ECM to complete the relearn process. Do not press any pedals or turn the ignition on during this time.
- Start engine: After 2 minutes, start the engine normally. It should run smoothly without any throttle-related issues. If the idle is still rough or unstable, repeat the relearn procedure.
- Test drive: Take the vehicle for a test drive spanning at least 10-15 minutes. Vary the engine speed and load to allow the ECM to fine-tune its adjustments. Avoid constant speeds and use different gears and throttle positions.
After completing the test drive, your Land Rover’s throttle body relearn should be complete. The ECM will have relearned the idle and throttle positions for optimum performance. If the pedal method does not resolve your throttle issues, you may need to use a diagnostic tool for a more comprehensive relearn, or there may be underlying faults that need to be addressed first, such as wiring issues, vacuum leaks, or a faulty throttle body.
Diagnostic Tool Method Throttle Relearn
For some Land Rover models, or if the pedal method is unsuccessful, you’ll need to use a diagnostic tool to perform the throttle relearn. The most common tool for Land Rovers is the IIDTool, which can communicate with the vehicle’s ECM to initiate the relearn process. Here’s a general overview of using the IIDTool for a throttle relearn:
- Connect diagnostic tool: Plug the IIDTool into your Land Rover’s OBD-II diagnostic port, usually located under the dashboard on the driver’s side.
- Turn ignition on: Put the key in the ignition and turn it to the “ON” position without starting the engine.
- Access ECM functions: Using the IIDTool menus, navigate to the Engine Control Module (ECM) functions.
- Select throttle relearn: Look for an option related to throttle relearn, such as “Throttle Position Reset” or “Idle Relearn”. Select this function.
- Follow prompts: The IIDTool will display instructions on the screen to guide you through the relearn process. This may involve depressing the accelerator pedal, turning the ignition on/off, or other steps. Carefully follow all the prompts.
- Clear fault codes: After the relearn is complete, use the IIDTool to clear any stored throttle-related fault codes in the ECM.
- Test drive: Disconnect the IIDTool and take your Land Rover for a test drive of at least 10-15 minutes. Vary the throttle positions and engine speeds to allow the ECM to fully adapt.
Using a diagnostic tool provides more precise control over the relearn process and can be helpful for troubleshooting stubborn throttle issues. However, it does require purchasing or borrowing the appropriate tool, which can be expensive. If you are uncomfortable using a diagnostic tool or don’t have access to one, consult a Land Rover service center or an independent shop specializing in Land Rovers. They will have the tools and expertise to perform the relearn properly.
Preparing for a Throttle Relearn
Before beginning the throttle relearn procedure on your Land Rover, it’s important to do some preparatory checks and ensure the vehicle is in good operating condition. This will help the relearn process go smoothly and avoid potential issues.
Check for Fault Codes
Using a diagnostic tool or code reader, scan your Land Rover’s ECM for any stored fault codes. If there are codes present, especially those related to the throttle body or air intake system, they should be diagnosed and repaired before attempting a relearn. Some common throttle-related fault codes include:
- P0121: Throttle Position Sensor Inconsistent with MAF Sensor
- P0122: Throttle Position Sensor Circuit Low Input
- P0123: Throttle Position Sensor Circuit High Input
- P1639: Throttle Adaption, Spring Test Failed
- P2119: Throttle Actuator Control Throttle Body
If any of these or other codes are present, investigate the cause and make necessary repairs. A throttle relearn will not fix underlying mechanical or electrical faults.
Inspect Throttle Body
Visually inspect the throttle body for any signs of damage, cracks, or excessive carbon buildup. If the throttle body is heavily contaminated, clean it with a throttle body cleaner spray and soft brush before proceeding with the relearn. Also check the throttle body wiring harness and connectors for any frayed wires, loose connections, or corrosion. Repair or replace any damaged components.
Check Vacuum Lines
Inspect all the vacuum lines connected to the throttle body and intake manifold. Look for any cracks, kinks, or loose connections that could cause a vacuum leak. A vacuum leak can cause idle issues and affect the relearn process. Replace any damaged vacuum lines and ensure all connections are secure. You can use a smoke test or spray carburetor cleaner around the vacuum hoses while the engine is running to check for leaks.
Clean Mass Airflow Sensor
The mass airflow (MAF) sensor measures the amount of air entering the engine and is a key input for the ECM to control the throttle body. If the MAF sensor is dirty or faulty, it can cause incorrect readings and affect throttle operation. Locate the MAF sensor, usually found in the air intake duct near the air filter box. Remove the sensor and carefully clean it with MAF sensor cleaner spray. Do not touch the delicate sensor elements inside. Reinstall the sensor securely.
Inspect Air Filter
Check the engine air filter for excessive dirt, debris, or damage. A clogged air filter can restrict airflow and cause throttle issues. Replace the air filter if necessary. Also inspect the air intake duct and housing for any cracks or leaks. Repair or replace any damaged components to ensure proper airflow.
Battery Voltage
A weak or failing battery can cause all sorts of electrical issues, including problems with the throttle body and ECM communication. Use a multimeter to check the battery voltage. It should be at least 12.6V with the engine off. If the battery voltage is low, charge it with a battery charger or replace it with a new one if it’s past its service life. Ensure the battery terminals and cables are clean and tight.
Idle Air Control Valve
The idle air control (IAC) valve is responsible for maintaining a stable idle speed by allowing a small amount of air to bypass the throttle body. If the IAC valve is stuck or faulty, it can cause rough idle or stalling. Locate the IAC valve, usually mounted on or near the throttle body. Remove it and clean it with throttle body cleaner spray. Make sure the valve moves freely and is not seized. Reinstall the valve and ensure the electrical connector is secure.
By completing these preparatory checks and repairs, you can ensure your Land Rover is in optimal condition before performing the throttle relearn. This will increase the chances of a successful relearn and reduce the likelihood of further issues.
Throttle Relearn Tips and Troubleshooting
While the throttle relearn process is generally straightforward, there are a few tips and tricks to keep in mind to ensure a successful outcome. If you encounter any issues during or after the relearn, here are some troubleshooting steps to try.
Tips for a Successful Relearn
- Battery voltage: Ensure the battery is fully charged and in good condition before starting the relearn. Low voltage can interfere with the process.
- No pedal input: During the relearn, do not press the accelerator or brake pedals unless instructed to do so. Any unexpected pedal input can confuse the ECM.
- Avoid electrical loads: Turn off all unnecessary electrical accessories like the radio, headlights, A/C, etc. during the relearn. Excessive electrical draw can affect the process.
- Patience is key: Follow the relearn steps carefully and wait the specified time periods. Rushing the process or skipping steps can lead to an incomplete relearn.
- Vary throttle on test drive: After the relearn, take a test drive and vary the throttle positions and engine speeds. This helps the ECM fully adapt to the new settings.
- Consult a professional: If you’re unsure about any steps or encounter issues, don’t hesitate to consult a Land Rover service center or experienced mechanic for assistance.
Troubleshooting Common Issues
- Rough idle persists: If the idle is still rough or unstable after the relearn, repeat the process and make sure to follow each step carefully. If the issue persists, check for vacuum leaks, clean the MAF sensor, and inspect the IAC valve.
- Fault codes return: If throttle-related fault codes reappear after the relearn, there may be an underlying issue with the throttle body, wiring harness, or ECM. Diagnose and repair the fault before attempting another relearn.
- Poor throttle response: If the throttle feels sluggish or unresponsive after the relearn, there may be an issue with the throttle position sensor or accelerator pedal position sensor. Check for fault codes and inspect the sensors for proper operation.
- Relearn not completing: If the relearn process seems to get stuck or not complete, there may be a communication issue between the ECM and throttle body. Check the wiring harness and connectors for damage. A diagnostic tool may be necessary to reset the ECM.
- Engine stalls during relearn: If the engine stalls or shuts off during the relearn process, there may be a serious issue with the throttle body or related components. Consult a professional for diagnosis and repair.
Remember, a throttle relearn is not a cure-all for every throttle issue. It’s important to diagnose and repair any underlying faults before attempting a relearn. If the problem persists after multiple relearn attempts and thorough troubleshooting, it’s best to seek the assistance of a qualified Land Rover mechanic.
Final Words from Boss Erwin
Performing a throttle relearn on your Land Rover can help restore proper throttle operation and idle quality after a throttle body cleaning or other service. By following the steps outlined in this guide and preparing your vehicle beforehand, you can successfully complete the relearn process at home. Remember to choose the appropriate relearn method for your specific Land Rover model, whether it’s the pedal method or using a diagnostic tool like the IIDTool. If you encounter any issues or are unsure about the process, don’t hesitate to consult a professional for assistance.