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Forum > Failed Smog Test > Question

1997 Ford F-150 Computer Memory Erased When Ignition Off

My1997 Ford F-150 will not pass smog test. Whenever I turn off the ignition the truck's computer resets and erases all the monitors. If I keep the truck running for an hour or so, after having driven it, the monitors will be complete and the truck will pass the smog check. Will I need to replace the computer?

Answer:

We would not suspect your Ford F-150's computer is defective until we've exhausted all other efforts in terms of power supply. Is your Ford trucks ECU getting 12 volts at all times? This is the question which needs to be answered. Check the power pin on the ECU. Start with the fuse box. Locate the ECU and DTL (Data Link Connector) fueses. You may have more than one ECU fuse. Make sure they are not blown. Your Ford F-150's engine control unit needs to have battery power at all times, even when the ignition is turned off. If at any time the ECU loses power its memory (and emission monitors) will be erased. Without "complete" or "ready" emission monitors your truck can not pass the smog test. Emission Monitors are internal self-tests which the computer performs in order to ensure the truck's emission systems are functioning properly. posted by SmogTips Support

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