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Old 03-27-2008, 08:08 AM   #4
Gerry Proctor
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Join Date: Oct 2002
Location: San Antonio, Texas
Posts: 2,682

2008 Astra XR
2008 SKY Red Line
Default Re: OBDII failed self test smog test failed

It could be a thermostat, but you should also be seeing a P0128 for failure of engine to come up to temperature fast enough. But that depends on the algorithm to set a code as it varies from car to car and from year to year. Considering the cost, it's worth replacing it to see if that addresses the issue.

What you really need to see is the mode 6 data as well as the freeze frame and pending codes. You will probably not be able to see (and probably won't be able to correctly interpret) these on the lower end scanners. So, without the benefit on that information, you will have to go with the most obvious or likely diagnostic paths and hope you guess right.

The non-continuous monitors need to see sensor data in acceptable ranges in order to successfully run. If one of the senors that contributes to the execution of the monitor test would cause it to fail the test, it won't run the monitor.

In your case, a coolant temp below requirements could very well not allow the monitors to complete since the system won't go into closed loop.


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