Q: Can't pass emissions test even though codes pass.

asked by on January 12, 2016

The car will not pass the emissions test. All of the codes seem to pass, but the computer doesn't go into Computer Ready status. No one can figure out why.

Hello, To get the readiness monitors to pass it requires driving the sometime in a different fashion than what you’re used to. To start, the fuel tank needs to be between 3/4 and 1/4 tank and the vehicle must be driving on the freeway at 55 MPH (set the cruise control) for about 5 miles. When you get off the freeway, pull over to a safe location shut off the engine and restart it. Let the car idle for a 2 minutes and get back on the freeway and return home doing 55 MPH. The reason for 55 MPH is that was law of the land when all this was written and the parameters were set. If you live in a large metropolitan area, you may need to go do this at night like 10 pm to be able to cruise at 55 MPH. Another great resource, if you know which readiness codes are not set, is to search the web for "GM drive cycle".

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