* Clear trouble codes: If you're dealing with a check engine light, you need to clear the diagnostic trouble codes (DTCs) stored in the ECU's memory. This doesn't reset the ECU itself, but it clears the stored fault history. This is done using a scan tool that can communicate with the vehicle's onboard diagnostics (OBD) system. OBD-I systems (like the one in your 1991 Silverado) require a specific scan tool; a generic OBD-II scanner won't work.
* Disconnect the battery: This is a common, albeit crude, method that sometimes helps resolve minor electrical gremlins. Disconnecting the negative battery terminal for about 30 minutes (or even overnight) will often clear volatile memory in the ECU. Important: This will reset things like radio presets, clock settings, and possibly other learned parameters. It's not a true "reset" in the sense of reflashing the ECU's firmware.
* Address the underlying problem: Resetting the ECU is a band-aid solution; it doesn't fix the actual problem causing the issue. If you have a check engine light, find out *why* it's on. A scan tool is essential for diagnosing OBD-I codes.
In summary: For a 1991 Chevy Silverado, the most effective method to address issues related to the ECU is to:
1. Use a scan tool: Diagnose the problem accurately by reading the trouble codes.
2. Repair the underlying problem: Address the root cause of the issue, not just the symptoms.
3. Disconnect the battery (as a last resort): Try this only if you've addressed the underlying problem and are still experiencing issues (though it's not a guaranteed solution).
A scan tool specifically designed for OBD-I systems is necessary for proper diagnosis and code clearing. Auto parts stores might be able to read the codes for a small fee, or you could invest in an OBD-I scan tool if you plan on working on your truck frequently. Remember, simply resetting the ECU won't fix a malfunctioning component.
