* Resetting the PCM (Powertrain Control Module): This is often the most common thing people mean when they talk about "resetting the computer" in older vehicles. The most reliable method is to disconnect the negative (-) terminal of the battery for about 30-60 minutes. This allows the computer's memory to clear completely. Reconnect the terminal and start the vehicle. The PCM will then relearn your driving habits.
* Other modules: Other modules like the Body Control Module (BCM) might also benefit from a battery disconnect, though this is less commonly done.
* Addressing specific issues: Instead of a general reset, if you're having a particular problem (e.g., a check engine light), you'll need to diagnose the issue itself. Simply resetting the PCM may not solve the underlying problem. A code reader (OBD-I scanner, specific to the year) is needed to understand why the check engine light is on.
Important Considerations:
* OBD-I: 1991 Wranglers use OBD-I (On-Board Diagnostics I), which is a much simpler system than modern OBD-II. Tools and procedures are different.
* Radio codes: Disconnecting the battery will likely erase your radio presets and might require you to enter a radio code to reactivate it. Write down your radio code *before* disconnecting the battery if you have it.
* Other electronic settings: Other settings, like your clock, might also reset.
In short, "resetting the computer" in a 1991 Jeep Wrangler means disconnecting the negative battery terminal for a period of time. However, this is a broad solution and might not address a specific problem. Diagnosing the actual issue is usually more effective than a generic reset.
