Jeep PC, ECM, And TCM Breakdown

Jeep PC, ECM, And TCM Breakdown


Cars are complex mechanical structures requiring many parts and operations to work in tandem to create motion. A vehicle’s complexity makes it very difficult for a person to determine a fault, and exactly for that reason, cars were computerized after 1996. Nowadays, you find cars fitted with electronic components that immediately detect a fault in the works. Compliments to the advanced computers, we have saved an immense amount of time, labor, and money. We call these control modules/units and they monitor different areas of the car. Let’s talk about different types of control modules and know the functions they perform.


ECM refers to Engine Control Module, also commonly known as ECU (Engine Control Unit). This system gathers data from the intake, exhaust, cooling system and other internal components to decide the fitness integrity of the engine. Subsequently, it delivers necessary electrical commands to decide the position of the camshafts and the throttle, ignition timing, fuel injection timing, and wastegate pressure (in turbocharged cars). This is achieved through programs developed independently by auto manufacturers such as Chrysler, Audi, and Mercedes. Each manufacturer has a distinct program.


TCM stands for Transmission Control Module. This computer system helps govern the shift timings, and by using sensor data from cruise control, throttle and traction control systems, it minimizes wheel spin, thus improving handling. TCMs can be found in dual clutch manual transmissions as well as electronically supervised automatics.


Powertrain Control Module (PCM) is basically a marriage between a TCM and ECM. It controls the functions of both TCM and ECM. The distinction here is that a PCM device analyzes sensor data as a single unit and so it deals with the input from the sensors intelligently resulting in increased power and fuel efficiency.

These self-taught machines adapt to the different environments and conditions. Later, they use learned data and apply it to the vehicle keeping in mind the driver’s driving habits. Bear in mind, ECU and TCM are independent systems having their own processor and ROM, and they share data whenever it is needed.

Where is the Main Computer Located?

There are two places the main computer can be found:

1. Below the hood

2. Under the dashboard

Depending on the design of the vehicle, each manufacturer will determine the best location to place the device. To find the computer, simply locate the engine wiring harness until you see the box like structure.

The computer can break down due to factors like abnormal vibrations, electrical surges due to faults in the battery, and moisture. Fortunately, for an everyday man, any malfunction that occurs in the car is given a code. The program finds the problem, remembers the code and triggers the check engine light. Use a code scanner; it is designed to extract information from the computer. After the problem is fixed, the code has to be cleared.

A ‘limp mode’ is programmed to reduce the car’s performance on the off chance that the car experiences a huge malfunction. Furthermore, there could be electrical wire shortage in the various links and connectors between the systems that must be repaired urgently.

Cost of the Computer and is it Replaceable?

Replacing the computer is possible and relatively easy on cars made before 1996. Newer cars have adaptable systems which allow data to be downloaded from the old computer into the new one courtesy of a capable scanner. However, buying a replacement computer can prove to be expensive. New computers range anywhere from $1,000 to $2,500 or more depending on the vehicle manufacturer. The cost-effective method is to acquire a computer from your local junkyard where it could cost between $350 and $600.


An unlocked Jeep PCM is required to install a Prodigy Turbo Kit on all Wranglers from 2015 and forward. Jeep locked all PCM's on the newer model Jeeps which prohibit the vehicle from accepting a custom tune. We provide an unlocked Jeep Wrangler PCM which allows you to write the Prodigy custom turbo tune to complete the installation.
Back to blog