Honda ECM/PCM Idle Learn Procedure

Very frequently I've been asked to look at datalogs of an erractic idle. Usually the blame lies with an aftermarket throttle body or even an OEM Honda throttle body. The tell tale signs are an idle that likes to "jump" up and down or "go crazy". After the break is the procedure to calibrate the idle. I've found that I get the best results if I start the procedure with the car cold (below 100 F ECT).

Then idle learn procedure must be done so the ECM/PCM can learn the engine idle characteristics.

Do the idle learn procedure whenever you do any of these actions:

-replace ECM/PCM
-Reset ECM/PCM
-Update ECM/PCM
-Replace or clean throttle body

Procedure

1. Make sure all electrical items (a/c, audio, lights, etc) are off.
2. Reset the ECM/PCM (pulling the power by unplugging the battery works well).
3. Turn the ignition switch ON (II), and wait 2 seconds.
4. Start the engine. Hold the engine speed at 3,000 rpm without load (in park or neutral) until the radiator fan comes on, or until the engine coolant temperature reaches 194 F (90 C).
5. Let the engine idle for about 5 minutes with the throttle closed. (NOTE: if the fan comes on, do not include its running time in the 5 minutes.

The biggest this I can say: be patient. If you don't get it just right, you may need to do the procedure a second time. Also, keep in mind that an erractic idle can also be caused by a vacuum leak.

Hope this helps.