My 2005 saturn ion has a p0300. i changed the ICM and it worked for a while but the same problem started again.

Question edited for clarity.
Question moved to model category.

You can't just replace it because it need programming for that car. It have to be programmed with the VIN Number and the mileage. There are very few reasons that you would ever change an ECU. The number is on a paper sticker on the outside.

https://www.google.com/search?q=2005+Saturn+Ion+2.2+ECU+location

https://www.google.com/search?q=auto+electrician+near+me

Speed Sensor

https://www.google.com/search?q=2005+saturn+ion+2.2+speed+sensor+replacement

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images for KNOCK SENSOR ON 2005 SATuRN

Where To Find The Knock Sensor 3 0 Litre Saturn Vue ...

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Where To Find The Knock Sensor 3 0 Litre Saturn Vue ... 2006Saturn Ion 2 2 liter P0300,P0128,P0326, and ...

Insert the key into the ignition and turn it to the "ON" position. There is no need to start the car.

2

Press the button located in the center of the instrument cluster ONCE. The display should now read "OIL LIFE" instead of vehicle mileage.

Read more: How to Reset the oil life monitor on a Saturn Ion ' eHow.com http://www.ehow.com/how_5658600_reset-life-monitor-saturn-ion.html#ixzz28jXOUbyz

The P0102 means Mass or Volume Air Flow Circuit Low Input
The P0101 means Mass or Volume Air Flow Circuit Range/Performance Problem
The P0300 means Random/Multiple Cylinder Misfire Detected
The P0171 means System too Lean (Bank 1)
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Ktag ecu programmer

Transmissions have "filters." It may need to be changed as the fluid may be dirty and clogging some of the pressure valves in the ******.

Check your catalina converter..Might be clogged

you can reset the oil light by turning the key to on, but not starting it, then push the gas to the floor twice, then again...it should say oil life reset

I am not a mechanic and have had no problems with my 2005 Ion-2 but at msn/autos I see that these can exhibit a starting problem because of the ignition switch which they recommend replacing. The part is around $40 & the labor is 1 hr.

Probably something shorting out. This is something that probably isn't going to be easy to figure out. You need someone that can diagnose it in person