2003 Sebring, Stratus & Eclipse 3.0L V6 ECM: A Guide to Swapping, Programming, and Misfire Fixes

Compatibility Warning: Read This First!

Symptoms of a Failing ECM

An ECM can fail in many ways, often leading to confusing symptoms that can mimic other problems. Diagnosing a bad ECM is frequently a process of elimination after checking more common failure points like sensors, spark plugs, and wiring.

• Check Engine Light: This is the most common symptom. The light may be on constantly, or it may flash, which can indicate a serious misfire. A flashing check engine light on these specific models can be a sign of a bad PCM.
• Engine Misfires or Stalling: The engine may run rough, stutter, hesitate, or stall unexpectedly. This can be caused by the ECM failing to correctly time spark or fuel injection.
• No-Start Condition: The engine may crank but refuse to start. This can happen if the ECM is not sending signals to the fuel injectors or ignition coils. 🎬 Watch: Diagnosing a no-fire condition caused by a bad ECM. It can also be caused by the anti-theft system if the ECM is not properly programmed to the vehicle.
• Poor Performance and Fuel Economy: You might notice a sudden drop in gas mileage or a significant loss of power and acceleration.
• Multiple Unrelated DTCs: A classic sign of a failing ECM is the sudden appearance of numerous, seemingly unrelated Diagnostic Trouble Codes (DTCs). For example, you might get codes for multiple different sensors all at once.

Is It a Bad ECM or Just a Software Issue? (TSB)

Before you replace your ECM, be aware of a Technical Service Bulletin (TSB) that applies to 2000-2003 Mitsubishi Eclipse models with the V6 engine (and by extension, the Sebring and Stratus coupes). TSB-02-13-015 (also NHTSA TSB 10001207) addresses an issue where incorrect software causes engine misfires (DTCs P0300-P0306), especially when the engine is cold or at high speeds. This condition is fixed by reprogramming (or 'reflashing') the existing ECM with updated software at a dealership, not by replacing the hardware. If your only symptoms are misfire codes, investigate this TSB first.

Diagnosing and Replacing the ECM

Location

On the 2003 Mitsubishi Eclipse, Chrysler Sebring Coupe, and Dodge Stratus Coupe, the ECM is located inside the vehicle, behind the passenger-side glove box. You will need to remove the glove box to access it. In some cases, a plastic HVAC air duct may also need to be removed 🎬 See this walkthrough for accessing and swapping the module. to get a clear path to the module and its connectors. This is different from the sedan versions of the Stratus and Sebring, which often have the ECM in the engine bay.

Replacement Steps (Overview)

1. Disconnect the Battery: Always disconnect the negative battery terminal before working on any electronic components.
2. Access the ECM: Open and remove the passenger-side glove box. Remove any trim panels or air ducts blocking access to the ECM.
3. Disconnect the ECM: Carefully unplug the wiring harness connectors from the old ECM. There are typically multiple large connectors with locking tabs.
4. Remove the ECM: Unbolt the ECM from its mounting bracket and remove it from the vehicle.
5. Install the New ECM: Mount the new ECM, reconnect the wiring harnesses, and reinstall any ducts or panels you removed.
6. Reconnect the Battery: Reconnect the negative battery terminal.
7. Programming/Immobilizer Relearn: This is the most critical step. The vehicle will not start until the replacement ECM is programmed to the car's immobilizer system. See the detailed section on programming below.

Buying a Used Engine Control Module (ECM)

A used OEM ECM is often the most cost-effective solution, but it comes with unique challenges. Unlike a simple mechanical part, you can't just swap it in.

• The Immobilizer Problem: The single most important thing to understand is that a used ECM is 'locked' to the donor car's anti-theft system (immobilizer). You cannot install a used ECM from another car and expect it to work without reprogramming. The car will crank but will not start, and a security light may flash on the dashboard.
• Solution 1: Professional Programming: The most common solution is to have the used ECM programmed to your vehicle after installation. This requires a dealer-level scan tool like the Chrysler DRB III or Mitsubishi MUT-II/III, or advanced tools used by some automotive locksmiths. They will write your car's Vehicle Identification Number (VIN) and security key information to the replacement ECM.
• Solution 2: The Matched Set: A great option for DIY replacement is to purchase a 'kit' from a donor vehicle. This includes the ECM, the immobilizer module (located around the ignition key cylinder), and the matching transponder key(s). By swapping all three components, you are essentially transplanting the entire matched security system from the donor car 🎬 Watch: How to replace the immobilizer and ECU together., bypassing the need for reprogramming.
• Solution 3: Pre-Programmed Modules: Several online retailers sell remanufactured ECMs that they will pre-program to your car's VIN before shipping. This makes the unit 'plug-and-play' upon arrival and is often the simplest, though more expensive, option.
• Part Numbers: You will see several part numbers for this application, including MR578718 and MR988513. While these are likely interchangeable, it is more important to verify that the part comes from a 2003 Coupe with a 3.0L V6 and manual transmission. Always confirm compatibility with the seller.

Cost of Replacement

Frequently Asked Questions (FAQ)