The quick answer: reset the PCM by disconnecting the negative battery cable, waiting about 15 minutes, then reconnecting and allowing the engine to relearn; you can also clear diagnostic trouble codes with an OBD-II scanner if you have one.
Manual reset: battery power cycle
This method clears the PCM’s learned memory and idle/fuel-trim adaptions by removing power to the control module. It’s a straightforward approach for many 1996 Cherokees and can help with intermittent drivability issues or a stubborn check engine light when the root cause isn’t diagnosed yet.
- Park the vehicle on a level surface, engage the parking brake, and turn off the engine.
- Disconnect the negative (-) battery cable first using a wrench to loosen the clamp. Keep the cable from touching the battery post or any grounded metal.
- Optionally, you may disconnect the positive (+) cable as well to ensure a full power cut, but this is not strictly required. If you do, avoid letting the terminals contact any metal surfaces.
- Wait about 10–15 minutes to allow capacitors to discharge and memory to clear.
- Reconnect the battery in reverse order: positive first, then negative. Ensure the connections are clean and tight to prevent arcing.
- Turn the ignition to ON (do not start) for a few seconds, then start the engine. Let it idle and then drive normally to allow the PCM to relearn idle and fuel trims through driving cycles.
- If your radio or other components were tied to the battery, you may need to re-enter radio or security codes.
After this reset, the PCM will generate new idle and fuel-trim data as you drive. If a check engine light returns, there may be an underlying fault that requires diagnosis rather than a memory reset.
Resetting codes with an OBD-II scanner
If you have access to an OBD-II scanner, you can clear stored trouble codes without a full power cycle. This is often faster and avoids losing other nonessential settings. Some monitors may still run and recheck after being cleared, so you should drive the vehicle afterward to complete the readiness checks.
- Locate the OBD-II diagnostic port under the dash on the driver’s side (16-pin connector).
- Plug in the scanner and turn the ignition to the RUN position (engine off unless the tool requires the engine to be running).
- Follow the scanner prompts to read codes, then select the option to Clear or Erase codes and/or reset monitors.
- Confirm if prompted. Once cleared, start the engine and drive normally to allow the PCM to re-run its monitors.
- Note any codes that reappear after a drive cycle; address the underlying issue if codes persist.
Using a scanner is a practical alternative for removing stored codes without a full battery power reset, but it does not guarantee the same level of memory clearance as a complete power loss and relearn scenario.
What to expect after a reset
Expect the PCM to relearn fuel trims and idle characteristics over several driving cycles. You may notice a temporary rough idle, richer or leaner idle behavior, or a change in how the engine responds as it re-optimizes fuel delivery. If the Check Engine Light remains on after reset and driving, a fault diagnostic is recommended to identify and repair the root cause.
Radio, security, and other systems
Battery disconnects can trigger radio anti-theft codes or other security features on older vehicles. Have your radio code handy from the owner’s manual or dealership records. If you’ve lost access codes, you may need to contact a dealer with your VIN to retrieve them.
When a reset may not help
A PCM reset does not fix mechanical problems or failing sensors. If performance issues persist, or if codes keep returning after the reset, a diagnostic inspection is warranted to identify faulty sensors (such as MAF, O2, or TPS), wiring problems, or vacuum/air leaks.
Summary
Resetting the PCM on a 1996 Jeep Cherokee can be accomplished with a manual battery power cycle or by clearing codes with an OBD-II scanner. Both approaches aim to refresh learned settings, but a persistent problem requires diagnosing the underlying cause. Always perform resets safely, be mindful of radio/security codes, and drive the vehicle to allow proper relearn of engine management parameters.