Jeep ECU (Car brain/computer) location and how to replace

Jeep ECU (Car brain/computer) location and how to replace. The electronic control unit is the computer that regulates the engine’s performance and fuel consumption. The ECU is located beneath the passengers’ seat in Jeep Cherokee, while it’s under the hood of Jeep Wrangler. The ECU controls ignition timing, air-fuel mixture, idle speed, throttle position, and other parameters to maintain a stable engine operation. The replacement procedure for this system consists of disconnecting battery cables from car terminals before removing bolts or screws securing the cover panel at the bottom side of the passenger seat or under the vehicle’s hood. In this blog post, we will explain in detail.


What is ECU?:

Jeep ECU (Car brain/computer)


The electronic control unit is the main processor for your vehicle. The ECU controls all major functions in a car, such as steering and acceleration. The ECU is also where many sensors and switches communicate. The powertrain, A/C, fuel injection system are all controlled by the ECU in your vehicle. The ECU is located in the engine bay, near the front of your vehicle. The ECU is protected by a metal case and mounted to the frame. The ECU measures about 18 inches long, 12 inches wide, and six inches high.


Where is it located?:

Jeep ECU (Car brain/computer)

The PCM (ECU) is located right behind the battery on the passenger side of the vehicle, attached to the firewall. The ECU is a small box with many connectors. The power connector is the one on top and it has six wires coming out of it, including ground. The other five are signals from sensors that tell the PCM what’s going on in front or behind the engine, like coolant temperature or intake air temperature.


How to replace Jeep ECU?


Jeep ECU ( Car brain/computer) location and how to replace. The Jeep Engine Control Module, known as the PCM ( Powertrain Control Module) ECU ( Electrical Control Unit ), or to simply put the Automotive Engine Computer. Confusing right? If you would like to know more about their differences you can read up on our previous post ” Difference between ECM, ECU & PCM ” which we covered in detail. Here is a little summary of it, where the body controls everything, and just like anything else you’re going to need resetting before testing its condition properly! To do this with your Jeep engine control module means following these steps:


– Turn off all unnecessary lights, including headlights, interior light of dashboard dials or meters (if you can turn them on without starting engine), radio presets; if it’s wintertime make sure that heat is also turned down as well as air conditioning(depending on weather). If you have a sunroof make sure it too is closed before turning everything else off.

– Remove battery power for at least 5 minutes; will allow time for all modules that are powered by voltage from battery unplugged to reset.

– With your headlights now on, you should turn them off and back on twice. It’ll allow the Engine Control Module to go into safe mode so it can be drained from any remaining power.

– Now plug back in the negative terminal and your Jeep ECM should now be reset. We still need to do a little more work on it though, but don’t worry because we’ll save all of our progress so you can come back any time!



  1. Disconnect the negative battery cable.
  2. Remove the coolant reserve/overflow tank (mounted on 1
  3. bolt and 2 nuts).
  4. Delicately unplug the three 32–way connectors
  5. at PCM.
  6. Remove the mounting bolts (3).
  7. Pull the PCM out.



  1. Examine all the pins in the three 32–way electrical connectors for damage. Make sure that they are all ok.
  2. Install PCM. Tighten the mounting bolts to 1 N·m (9 in. lbs.) torque (3 bolts).
  3. Mount coolant reserve/overflow tank.
  4. Connect the negative cable back to the battery.


1997 or 1998 Jeep Wrangler
Flashmasters 1997 Grand Compatible with Cherokee 4.0L Computer
Flashmasters 2000 Compatible with Grand Cherokee 4.0L Computer
Flashmasters 2005 Grand Compatible with Cherokee 4.7L Computer
Flashmasters 2008 Patriot 2.4L Engine
Innovative Performance Chip/Power Programmer compatible with Jeep Wrangler 2.0L, 2.4L, 2.5L, 3.0L, 3.6L, 3.8L, 4.0L and 4.2ptima Batteries


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