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Discussion Starter #1 (Edited)
This is the BMW E46's computer/monitor reset procedure.

For those of who have the "service engine soon" light coming on frequently preventing you from getting the sticker, read this. If you can get your car to pass this test once without the light coming on, bring it right to the mechanic and get it inspected.

This is taken directly from what seems to be a translated document from BMW, pulled up under a search for my car. I've highlighted important things by putting them in bold.

My mechanic recommended having the fuel tank between 1/4 and 3/4 full for this test.

2002 BMW 330XI 3.0L 225HP L6 M54 GAS-FI-N

ALL MONITORS - ALL MODELS, ALL ENGINES

Notes:
1. All tests can be completed in one driving cycle. Depending on driving style, more than one repetition may be required.
2. The drive cycle consists of engine start-up, vehicle operation (exceeding starting speed), coasting and stopping the engine.

Conditions:
1. The drive cycle will be interrupted if (a) engine speed exceeds 3000 rpm, (b) road speed exceeds 60 mph or (c) large fluctuations in accelerator pedal position occur.
2. This drive cycle will test all systems monitored once/drive cycle.

Steps:
1. From cold start, start the engine and idle for approximately 3 minutes. This step will evaluate the Secondary Air System and Evaporative Leak Detection (LDP-equipped vehicles).
2.Drive the vehicle for approximately 4 minutes at 20-30 mph, to enter "Closed Loop" status. This step will evaluate the response and switching time of the O2 sensors.
3. Drive at 40-60 mph, (but do not exceed 60 mph) for approximately 15 minutes. Include sufficient vehicle coasting phases. This step will evaluate Catalytic Converter Efficiency and response and switching time of O2 sensors.
4. Stop the vehicle and idle for approximately 5 minutes. This step will further evaluate the tank Leak Diagnosis.
5. Check the readiness codes with a generic or DISplus/MoDIC scan tool. 0 = Not completed or Not Applicable. 1 = Test Completed. EGR and Air Conditioning are Not Applicable.
6. If necessary, repeat Steps 1-5.

I hope this helps someone.
 

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This also assumes you are dealing with a "good" car and decent responding O2 sensors.

I can tell you typically I expect to see all Readiness Monitors clear after 2 cold starts, 3/4 tank of fuel and 15-20 minutes of steady highway driving on a good car.

The problem you have is many expect this to work like a charm, often it will not due to issues with the car/O2 sensors.
 

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Discussion Starter #4
Results: My car reset after one cycle. The only thing causing the light to come on is the thermostat (for the coolant - not the engine). That's on now, but it did make it through the DMV computer without lighting up.
 

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Results: My car reset after one cycle. The only thing causing the light to come on is the thermostat (for the coolant - not the engine). That's on now, but it did make it through the DMV computer without lighting up.
Are we talking about a low coolant light or a SES/CEL/MIL for a MAP thermostat problem?

P0128 is a very common thermostat failure code, there are a few others.

Suggest you read this thread - http://forum.e46fanatics.com/showthread.php?t=964491
 
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