How do you reset the Ecm or computer on a 95 jetta gls w 2 liter engine?

There's no single "reset" button for the ECM (Engine Control Module) on a 1995 VW Jetta GLs 2.0L. The method to clear trouble codes and potentially reset learned parameters varies slightly depending on the exact details of your car's system (OBD I vs. later systems), but generally involves these approaches:

1. Disconnecting the Battery: This is the simplest method and often effective for minor issues.

* Procedure: Disconnect the negative (-) battery terminal. Wait at least 30 minutes (some recommend longer, even up to an hour or overnight). Reconnect the negative terminal. This clears the computer's volatile memory, including things like learned fuel trims and shift points. It will *not* erase permanent fault codes stored in the ECM.

2. Using a Scan Tool: This is the preferred method because it allows for specific code clearing.

* You'll need a scan tool that's compatible with OBD I (likely). OBD I is the older diagnostic system used in your vehicle's year. A generic OBDII scanner *may* not work, though some can be adapted. A VW-specific scan tool would be best.

* Procedure: Connect the scan tool, read any trouble codes, and then use the tool's function to clear the codes. This is a more precise reset.

3. "Key Cycling" (Less Reliable): This method's effectiveness is questionable and often only works for very simple issues.

* Procedure: Turn the ignition key to the "ON" position (without starting the engine), wait for a few seconds, then turn the key to the "OFF" position. Repeat this cycle several times (5-10 is common). This might clear some minor faults but is not guaranteed to work.

Important Considerations:

* Check Engine Light (CEL): If the CEL is on, *do not* just reset the system without knowing why the light came on. Ignoring a CEL means ignoring a potential problem that could cause further damage. Diagnose the underlying issue first.

* OBD I limitations: OBD I systems offer limited diagnostic capabilities compared to later systems.

* Professional help: If you're not comfortable working on your car's electrical system, it's best to take it to a qualified mechanic for diagnosis and repair.

In summary, disconnecting the battery is the easiest starting point, but a scan tool is the most reliable method for a thorough reset and diagnosis. Remember to address any underlying problems indicated by trouble codes rather than just resetting the system.