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Forum > Failed Smog Test > Question

1997 Chevy S-10 not communicating with the smog check machine, why?

Vehicle passed pre-smog test but would not communicate when connected for the real test. The vehicle has not been driven for at least the last three months.
Answer:

Having sat for 3 months could have erased the Emission Monitors. We recommend driving your Chevy S10 for 2 to 3 weeks and then getting a retest. If there is still a communication problem, your S10 might in fact have a problem at the OBD II connector or with the emissions computer. If a smog repair station can connect a scan tool to your Chevy and retrieve emissions information from the computer, it can be safe to assume the problem is with the emissions monitors and not the OBD II connector. If a smog station can not connect a scan tool and retrieve any computer information then obviously there is an electrical communication problem, and there is no need to wait 2-3 weeks for a retest; just have a repair shop diagnose the communication problem now and save time. Your Chevy S10's emissions "monitors" indicate that certain emissions systems which the OBD II computer has been monitoring have PASSED the test, indicating that those systems are working properly. Technically the monitors not being set should not cause a communication problem, so we recommend you have a smog repair station conduct the communication diagnosis first... Or if you have time drive your Chevy for a few weeks and take it from there. posted by SmogTips Support

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