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Smog Check Repair

Ford Explorer Malfunction Indicator Lamp ON

I just bought a 1997 Ford Explorer. I went to get a smog check for the DMV and it failed the smog check. It passed the smog test last year but failed now. The smog report says my Ford Explorer failed because of the System Malfunction Light.

I looked up what that could be and found that the smog machine looks to see if the Check Engine Light is on, or on older Ford Explorers, the smog technician manually inspects for the light and then enters the results into the smog machine. 

My Ford Explorer's check engine light appears to be working and it is currently not on. What worried me was that the smog tech said my SUV didn't passed before he even printed out the vehicle inspection report.

Could the reason my Ford didn't pass the smog check be due to the check engine light even if the check engine light is working and also do you think the smog tech was trying to do something to rip me off?


There are two scenarios which would cause your Ford Explorer to fail the functional portion of the smog check which inspects for any Malfunction Indicator Lamp trouble.

In the first possibility, via the OBD II Data Connector Link, the smog machine may detect an active, pending, hard or soft OBD-II trouble code during the smog test; causing a smog check failure. It is not necessary for the Malfunction Indicator Lamp to currently be illuminated in this scenario. The MIL light may have been illuminated recently, and have gone undetected. If the light fails to return, and upon 3 drive cycle completions, the pending or soft trouble code should disappear; allowing your Ford Explorer to pass the smog check.

If the MIL light does illuminate over the course of the next 2 weeks, a "hard fault" exists and should be diagnosed by a smog check repair station. The station will retrieve the trouble code(s) from your Ford Explorer's ECU and inspect the problem further.

In the second scenario your Ford may fail for Malfunction Indicator Lamp trouble if the smog machine detects certain required Emission Monitors (also known as readiness flags) are "Not Ready" or "Not Complete".

In order to "Ready" or "Complete" the required emission monitors the OBD II system must complete at least one good drive cycle. A Drive Cycle is a sequence of internal tests which the OBD II computer runs while you are driving your Ford Explorer. These self tests ensure all emission systems are functioning properly. Emission monitors are erased often on vehicles which have had recent repairs requiring disconnecting of the battery, and/or the emissions computer. Disruption of 12+ power to the ECU clears all readiness flags. These vehicles will need to be driven in order to complete the required monitors.

posted by SmogTips Support 02-18-2014 04:11 PM

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