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MikeD', Technician
Category: Car
Satisfied Customers: 696
Experience:  ASE Cert, AS Degree in Automotive Diagnostics
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I have a 2001 Kia Rio. The check engine light comes on ...

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I have a 2001 Kia Rio. The check engine light comes on off and on. I took it in and had the coil replaced. it was fine for a while, but started doing it again. Once the coil was replaced the car runs great... and gets great gas milage, buit now the car wont smog. The computer will not talk to the smog equiptment. what will cause this?
Submitted: 9 years ago.
Category: Car
Expert:  MikeD' replied 9 years ago.
Do you have the engine code it is setting.
Customer: replied 9 years ago.
no. the last ime I had it in they said it was a knock sensor, but though it was a result of the bad coil. when the repair was finished the code cleared.
Expert:  MikeD' replied 9 years ago.

A coil will not set a knock sensor fault in this vehicle. Knock sensor faults are set when the vehicle is running extremely lean to the point of detonation setting a "knock" causing the ecu to retard timing. The most likely cause of your vehicle setting a knock sensor fault and not passing emissions "most likely due to high NOx" is a stretched timing belt, you will need to have your timing belt replaced soon to prevent serious engine damage.

Customer: replied 9 years ago.
would a trouble code cause the computer to not communicate with the Smog stations equiptment?
Expert:  MikeD' replied 9 years ago.

Possibly, but they probably communicated, they will fail you if there are any emissions related fault codes such as misfires, knock sensor, O2 sensor ect. You probably also had high levels of NOx gas coming from the tailpipe as well.

Customer: replied 9 years ago.
I was specifically told that they did not communicate.... three times now. I have not actually failed a smog. could never get that far.
Expert:  MikeD' replied 9 years ago.
You may have a faulty ECU causing this. It should communicate if the ECU is working properly. This would explain your other codes as well. I would have it scanned for fault code by the person that did it for you before to make sure it communicates with that scan tool. If you can read fault codes there is no reason that the Smog equipment would not work. They use a similar OBD 2 scan tool.
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