Honda Throttle Relearn Procedure: A Comprehensive Guide
If you own a Honda vehicle, you may have heard of the “throttle relearn procedure” or “idle learn procedure”. This is an important process that needs to be performed in certain situations to allow the vehicle’s engine control module (ECM) or powertrain control module (PCM) to relearn the engine’s idle characteristics. Performing this procedure correctly can resolve various drivability issues and ensure your Honda runs smoothly.
In this comprehensive blog post, we’ll cover everything you need to know about the Honda throttle relearn procedure, including:
- What it is and why it’s necessary
- Which Honda models it applies to
- Step-by-step instructions for performing the procedure
- Troubleshooting tips
- The latest information from Honda
By the end, you’ll be equipped with the knowledge and confidence to do the throttle relearn on your own Honda if needed. Let’s dive in!
What is the Honda Throttle Relearn Procedure?
The throttle relearn procedure (also known as the idle learn procedure or ECM/PCM idle learn procedure) is a routine that allows your Honda’s engine computer to recalibrate itself and “relearn” the engine’s idle characteristics. During this process, the computer monitors the engine at a specified RPM to determine the appropriate idle speed and air/fuel mixture.
Why is the Throttle Relearn Necessary?
There are a few reasons why you may need to perform a throttle relearn on your Honda:
- You replaced the ECM/PCM
- You reset or reflashed the ECM/PCM
- You replaced or cleaned the throttle body
- You disconnected the battery
- You’re experiencing an erratic or unstable idle
In any of these cases, the engine computer needs to be reset and the idle characteristics need to be relearned for proper operation. If the throttle relearn is not done, you may experience issues like a rough idle, stalling, hesitation, or poor throttle response.
It’s important to note that simply erasing diagnostic trouble codes (DTCs) with a scan tool does not require doing a throttle relearn on its own. The relearn procedure is only necessary for the specific situations outlined above.
Which Honda Models Use the Throttle Relearn Procedure?
The throttle relearn applies to many Honda models from the early 2000s onwards that use an electronic throttle control system. This includes but is not limited to:
- Accord (2003+)
- Civic (2001+)
- CR-V (2002+)
- Element (2003+)
- Fit (2007+)
- Insight (2000+)
- Odyssey (2005+)
- Pilot (2003+)
- Ridgeline (2006+)
- S2000 (2000+)
If you have one of these Honda models or a newer vehicle, it likely has an electronic throttle control and will require a throttle relearn when the battery is disconnected or the computer is reset. Older Hondas with a mechanical throttle cable do not need this procedure.
Step-by-Step Throttle Relearn Instructions
Here are the steps to perform the throttle relearn procedure on most Honda vehicles:
- Make sure all electrical accessories are turned off, including the A/C, audio system, lights, rear defogger, etc.
- If you disconnected the battery or replaced the computer, reconnect the battery cables or install the new ECM/PCM. Turn the ignition on (key in “run” position) and wait at least 2 seconds.
- Start the engine and let it idle until the cooling fans cycle on and off. This may take up to 15 minutes depending on the engine temperature. Do not turn on any electrical accessories during this time.
- Once the fans have cycled, hold the engine speed steady at 3,000 RPM (in park or neutral) until the cooling fans come on again or the coolant temperature reaches 194°F (90°C). This allows the computer to learn the engine load characteristics.
- Release the throttle and let the engine idle normally for at least 5 minutes. If the cooling fans cycle on during these 5 minutes, wait for them to turn off before continuing to idle. The computer is learning the idle characteristics during this time.
- After 5 minutes of idling with no fan activity, turn off the engine. The throttle relearn procedure is complete.
It’s crucial to follow these steps exactly for the computer to properly relearn the engine’s idle. Make sure not to touch the accelerator pedal or turn on any accessories until the 5-minute idle period is over.
If you have a scan tool, you can also initiate the relearn procedure through the tool on some models. Consult your vehicle’s factory service manual or a Honda dealer for the exact steps, as the procedure may vary slightly between different years and models.
Troubleshooting Throttle Relearn Issues
In most cases, carefully following the steps outlined above will result in a successful throttle relearn and restore proper engine operation. However, there are a few things that can go wrong:
Unstable Idle After Relearn
If your Honda’s idle is still rough or unstable after performing the relearn procedure, there may be an underlying issue with the idle air control system, vacuum leaks, or the throttle body itself. A dirty or sticking idle air control valve or a vacuum leak can cause idle issues even after the computer has relearned the idle.
Double-check all vacuum hoses for cracks or loose connections. Clean the throttle body and idle air control valve if needed. In some cases, the throttle body itself may be faulty and require replacement.
Check Engine Light On
If the check engine light comes on during or after the relearn procedure, there may be a problem with one of the engine’s sensors or systems. Use a scan tool to check for diagnostic trouble codes (DTCs). Common culprits include:
- Mass airflow sensor (MAF)
- Manifold absolute pressure sensor (MAP)
- Throttle position sensor (TPS)
- Idle air control valve (IACV)
- Coolant temperature sensor (ECT)
Address any stored codes before attempting the relearn procedure again. If the codes keep coming back, further diagnosis and repair will be needed.
Throttle Relearn Won’t Complete
In some cases, the throttle relearn procedure may not seem to complete successfully. The idle may stay high or fluctuate even after following the steps correctly. This can happen if one of the engine’s sensors is faulty or there is an issue with the idle control system.
Again, check for any stored trouble codes and address them first. Inspect the throttle body, clean the idle air passages, and make sure the throttle plate moves freely. If the problem persists, more in-depth diagnostic work may be required.
The Latest Honda Throttle Relearn Information
As of 2023, the throttle relearn procedure remains largely the same as it has been for the past two decades on Honda vehicles. The core steps of holding the engine at 3,000 RPM until the fans cycle and then letting it idle for 5 minutes are consistent across most models.
However, there have been a few updates and clarifications from Honda over the years:
- On some newer models, the procedure may be initiated through a scan tool instead of following the manual steps. Check with your dealer or consult the factory service information for the latest details on your specific vehicle.
- Honda has emphasized that the throttle relearn is not necessary after simply erasing trouble codes with a scan tool. The relearn should only be done when the battery is disconnected, the computer is reset/reflashed, or the throttle body is cleaned/replaced.
- For the most accurate relearn, Honda recommends having the engine fully warmed up first. If the fans have already cycled twice and the engine is at operating temperature, you can skip the 3,000 RPM step and go straight to the 5-minute idle.
- On drive-by-wire models, never open the throttle plate manually while the throttle body is connected. This can damage the delicate throttle position sensors. Always disconnect the throttle body before manually cleaning the throttle plate and bore.
By staying up to date on the latest service information from Honda, you can ensure you’re performing the throttle relearn procedure correctly on your vehicle. When in doubt, consult a factory service manual or contact a Honda dealer for assistance.
fINAL Words from Boss Erwin
The Honda throttle relearn procedure is a critical process that allows the engine computer to recalibrate itself after being reset or having the throttle body cleaned/replaced. By following the steps carefully and understanding when the procedure is necessary, you can avoid drivability issues and keep your Honda running smoothly.
Remember to:
- Only perform a relearn when needed (battery disconnected, ECM reset, throttle body cleaned)
- Make sure all accessories are off before starting
- Hold RPM at 3,000 until fans cycle, then idle for a full 5 minutes
- Address any check engine lights or codes before attempting a relearn
- Consult the factory service information for the latest details on your specific model
With patience and attention to detail, you can successfully complete the throttle relearn procedure and restore optimal performance to your Honda’s engine. By understanding this process, you’ll be better equipped to maintain your vehicle and diagnose any issues that may arise.