Throttle Body Relearn Nissan: Your DIY Guide to Smooth Idle After Cleaning

Cleaning your Nissan’s throttle body can significantly improve engine performance and fuel efficiency. However, after cleaning, your car might experience idle issues if you don’t perform a throttle body relearn. This process, also known as Idle Air Volume Learning (IAVL), is crucial for your Nissan’s Engine Control Unit (ECU) to recalibrate and ensure a smooth idle. While some procedures might suggest using a Nissan OBD scanner for this process, this guide will walk you through a DIY method to perform a throttle body relearn on your Nissan without needing specialized scan tools in many cases.

Understanding Nissan Throttle Body Relearn

The throttle body regulates the amount of air entering your engine. Over time, it can accumulate carbon deposits, affecting airflow and leading to an improper idle. Cleaning the throttle body resolves this, but it also changes the airflow characteristics. The ECU, which controls the engine’s idle speed, needs to “relearn” the new throttle body position to maintain the correct idle speed. Without this relearn process, you might experience symptoms like:

• High Idle: The engine idles at a higher RPM than normal.
• Pulsating Idle: The idle speed fluctuates up and down.
• Check Engine Light (CEL): Often accompanied by a P0507 code indicating high idle.

While advanced diagnostic tools like a Nissan OBD scanner can streamline certain relearn procedures, Nissan also provides a manual method that you can perform at home. This guide focuses on this manual, step-by-step process.

Preparing Your Nissan for Throttle Body Relearn

Before starting the relearn procedure, ensure your Nissan meets these preparation steps:

1. Engine Cold: Begin with a completely cold engine.
2. Normal Operating Temperature (Later Step): You’ll need to warm up the engine to normal operating temperature (160-203°F or 70-95°C) later in the Idle Air Volume Learning process. Driving your car for at least 30 minutes is recommended to achieve this consistently. Idling in your garage may not suffice.
3. Turn Off Accessories: Ensure all electrical accessories are turned off. This includes the air conditioning, headlights, rear defogger, radio, and blower motor. These can place a load on the engine and interfere with the relearn process.
4. Wheels Straight: Make sure your vehicle’s front wheels are pointing straight ahead.
5. No Check Engine Light for Related Issues: Ensure there are no existing Check Engine Light codes related to the mass airflow sensor, manifold absolute pressure sensor, or incorrect idle speed before proceeding. Address these issues first.

Once your Nissan is prepared, you can proceed with the following relearn procedures in sequence. It’s helpful to have a stopwatch or timer showing seconds for accurate timing.

Nissan Throttle Body Relearn Procedures: Step-by-Step

This process involves three key procedures that must be performed in order: Accelerator Pedal Released Position Learning, Throttle Valve Closed Position Learning, and finally, Idle Air Volume Learning.

1. Accelerator Pedal Released Position Learning

This step teaches the ECU the fully released position of the accelerator pedal.

1. Ensure Accelerator Pedal is Released: Make absolutely sure the accelerator pedal is not being pressed.
2. Ignition ON, Wait 2 Seconds: Turn the ignition switch to the “ON” position (do not start the engine) and wait for at least 2 seconds.
3. Ignition OFF, Wait 10 Seconds: Turn the ignition switch to the “OFF” position and wait for at least 10 seconds.
4. Ignition ON, Wait 2 Seconds: Turn the ignition switch back to the “ON” position and wait for at least 2 seconds.
5. Ignition OFF, Wait 10 Seconds: Turn the ignition switch to the “OFF” position again and wait for at least 10 seconds.

2. Throttle Valve Closed Position Learning

This procedure teaches the ECU the closed position of the throttle valve.

1. Ensure Accelerator Pedal is Released: Verify the accelerator pedal is fully released.
2. Ignition ON: Turn the ignition switch to the “ON” position.
3. Ignition OFF, Wait 10 Seconds: Immediately turn the ignition switch to the “OFF” position and wait for at least 10 seconds. During this time, you might hear a faint operating sound from the throttle body, indicating the valve is moving.

3. Idle Air Volume Learning (IAVL)

This is the crucial step where the ECU learns the correct idle air volume.

1. Engine COLD, Perform Initial Procedures: If the engine is cold, first complete both the “Accelerator Pedal Released Position Learning” and “Throttle Valve Closed Position Learning” procedures described above.
2. Warm Up Engine: Warm up the engine and transmission to normal operating temperature by driving for at least 30 minutes. Ensure it reaches 160-203°F (70-95°C).
3. Park and Turn Off Accessories: Park the car in a safe location, turn off all electrical accessories, and ensure the wheels are straight.
4. Ignition OFF, Wait 10 Seconds: Turn the ignition switch to the “OFF” position and wait for at least 10 seconds.
5. Ignition ON & Start Timer: Turn the ignition switch to the “ON” position (do not start the engine) and simultaneously start your stopwatch or timer.
6. Pedal Press and Release (5 Times): At the 3-second mark on your timer, fully depress and fully release the accelerator pedal quickly five times within 5 seconds.
7. Wait 7 Seconds, Then Pedal Down (20 Seconds): Wait for 7 seconds or more. Then, fully depress the accelerator pedal and hold it down for approximately 20 seconds or more. Watch for the Check Engine Light (MIL – Malfunction Indicator Lamp). It should start blinking and then turn solid ON. If the CEL doesn’t blink, you may need to repeat the entire IAVL procedure from the beginning.
8. Release Pedal (Within 3 Seconds of Solid CEL): Within 3 seconds after the Check Engine Light stops blinking and turns solid ON, release the accelerator pedal fully. This timing is critical.
9. Start Engine Immediately: Immediately start the engine and let it idle. The idle might initially be high or pulsating.
10. Idle for 20 Seconds, Then Rev: Let the engine idle for at least 20 seconds. Then, rev the engine two or three times to check if the idle speed stabilizes.
11. Check Idle in Drive and Park: With your foot on the brake, shift the car into “Drive.” The idle speed should decrease and be below 1000 RPM. Shift back to “Park.” The engine should now be idling at its regular, correct speed.

After completing these steps, the throttle body relearn process should be finished. In many cases, the Check Engine Light (CEL) will turn off on its own after successful IAVL. If it remains, you can attempt the following procedure to reset it.

Easy Reset of Check Engine Light (CEL) (If Needed)

If the Check Engine Light persists after the IAVL procedure, try this reset method:

1. Ignition OFF, Wait 10 Seconds: Turn the ignition switch to the “OFF” position and wait for at least 10 seconds.
2. Ignition ON, Pedal Press and Release (5 Times): Turn the ignition switch to the “ON” position (do not start the engine), wait 3 seconds, and then quickly fully press and release the accelerator pedal five times.
3. Wait 10 Seconds, Then Pedal Down (12 Seconds): Wait for 10 seconds. Then, fully depress the accelerator pedal and hold it down.
4. Release Pedal When CEL Blinks: After approximately 12 seconds, the Check Engine Light should turn off and then start blinking. As soon as it starts blinking, release the accelerator pedal.
5. Wait 10 Seconds, Pedal Down Again (10 Seconds): Wait for 10 seconds. Then, fully depress the accelerator pedal again and hold it down for 10 seconds.
6. Release Pedal Again: Release the accelerator pedal.
7. Ignition OFF, Then Start Engine: Turn the ignition switch to the “OFF” position. Then, immediately start the engine. The Check Engine Light should now be off.

Nissan Idle Relearn Procedure Chart: Visual guide for performing accelerator pedal and throttle valve position learning.

Conclusion

Performing a throttle body relearn on your Nissan after cleaning is essential for maintaining optimal engine performance and fuel efficiency. While some situations might benefit from using a Nissan OBD scanner for diagnostics or more complex relearn procedures, this manual method can be effective for many DIYers. By carefully following these step-by-step instructions and paying close attention to timing, you can successfully complete the Nissan throttle body relearn process and restore a smooth, consistent idle to your vehicle. If you encounter difficulties or are unsure about any step, consulting a professional mechanic or using an OBD scanner for Nissan specific diagnostics may be advisable.