1999 Mitsubishi Galant ECM: Decoding Part Numbers and Immobilizer Secrets
Your guide to identifying the correct Engine Control Module for your 1999 Galant and navigating the critical programming steps required to get your car running again.
- A replacement ECM for a 1999 Galant MUST be programmed to the vehicle's immobilizer system, otherwise the engine will not start.
- You must match the OEM part number from your original module exactly. Pay close attention to transmission (manual/auto) and emissions (federal/California) variants.
- The most common failure symptoms are a crank-no-start condition, intermittent stalling, and a Check Engine Light with internal fault codes like P0601.
- Programming can be done by a Mitsubishi dealer, some automotive locksmiths, or by using a mail-in cloning service. A DIY swap without programming will not work.
Critical: Immobilizer Programming is Required
Warning: You cannot simply swap the Engine Control Module (ECM) on a 1999 Mitsubishi Galant. The vehicle will crank but will not start. This is because the ECM is part of the vehicle's anti-theft immobilizer system.
The 1999 Galant uses a security system that requires the ECM, the ignition key's transponder chip, and the immobilizer module to all be electronically matched. When you install a replacement ECM, it still contains the security information from its donor vehicle. Your car will detect this mismatch and prevent the engine from starting as a theft-prevention measure.
To make a replacement ECM work, it must be programmed to your vehicle's specific Vehicle Identification Number (VIN) and synced with your existing keys and immobilizer module. This process requires specialized equipment:
- Mitsubishi Dealer: A Mitsubishi dealership can perform the programming using their proprietary MUT-II or MUT-III diagnostic scan tool.
- Automotive Locksmith: Some specialized locksmiths have advanced tools that can program Mitsubishi keys and modules.
- Mail-In Service: You can send your original ECM and the replacement unit to a service that will clone the data from your old module to the new one, making it plug-and-play.
- Matched Set: Another option is to purchase a complete, matched set from a single donor vehicle. This set must include the ECM, the immobilizer module, the ignition cylinder, and the original key. When installed together, these parts are already programmed to work with each other.
Symptoms of a Failing 1999 Galant ECM
A failing ECM can cause a wide range of confusing and intermittent problems. Because the ECM controls so many functions, its failure can sometimes be misdiagnosed as a bad sensor or other component.
- Crank, No Start: The engine turns over but never fires up. This is one of the most common symptoms.
- Intermittent Stalling: The engine shuts off unexpectedly while driving.
- Rough Idle or Misfiring: The engine runs poorly, shakes, or hesitates during acceleration.
- Check Engine Light: The light may be on with codes pointing to an internal module failure, such as P0601 (Internal Control Module Memory Checksum Error). You may also see multiple, unrelated sensor codes at once.
- No Communication with Scan Tool: A diagnostic scanner cannot connect to the ECM, indicating a complete internal failure.
- Transmission Shifting Problems: The automatic transmission may shift harshly or at the wrong times, as the ECM plays a role in transmission control.
Pro Tip: Before condemning the ECM, always check the basics first. Ensure the battery is fully charged and the terminals are clean. Also, inspect all related fuses and check for bad ground connections to the module, as low voltage can mimic ECM failure.
Buying a Used 1999 Galant ECM: A Buyer's Guide
Buying a used OEM ECM is often the most cost-effective solution, but careful matching is essential to avoid compatibility issues. New units are typically no longer available, and aftermarket options can be expensive.
How to Verify Compatibility
The single most important rule is to match the OEM part number on your original ECM exactly. The part number is printed on a label on the module's case. Small differences in part numbers can mean major differences in software for the engine, transmission, and emissions system.
The provided initial data highlights several key variations you must account for:
- MD355246 / E2T67683: Fits 1999 Galant with a 2.4L engine and Manual Transmission.
- MD355245: Fits 1999 Galant with a 2.4L engine and Automatic Transmission.
- MD355244 / E2T67683: Fits 1999 Galant with a 2.4L engine, Automatic Transmission, and California Emissions.
- MD355248: Fits 1999 Galant with a 2.4L engine and California Emissions.
- MD369101: Must be matched exactly.
Always verify the part number on your car's original unit before purchasing a replacement.
Physical Inspection
When inspecting a used ECM, look for:
- No Water Damage: Check the case and connectors for any signs of corrosion or water intrusion.
- Intact Connectors: Ensure all pins are straight and not bent, broken, or corroded.
- Unopened Case: Look for signs that the case has been pried open, which could indicate a failed repair attempt.
A common failure point for ECUs from this era is leaking internal capacitors. While you can't see this without opening the case, it's a known issue that can often be repaired by a specialist.
Known Issues, Recalls, and TSBs
While there are no specific recalls for the Engine Control Module itself on the 1999 Galant, there are related items to be aware of:
- NHTSA Recall 99V333001: On some V6 models, the battery cable harness could be damaged by heat from the exhaust manifold, causing grounded circuits. This could lead to a no-start condition by blowing the main fuse. While this is not an ECM failure, its symptoms could be similar.
- TSB-02-13-015: For 1999-2002 Galant V6 models, a technical service bulletin was issued to reprogram the PCM to fix cold engine misfires that could set codes P0300-P0306. This involves a software update, not a hardware replacement.
Cost Breakdown
Prices can vary significantly based on the source and required services. All replacement options will require programming unless you buy a pre-programmed unit or a matched set.
| Part/Service | Estimated Cost | Notes |
|---|---|---|
| New OEM | null | Generally no longer available. |
| Remanufactured | $250 - $450 | Often comes pre-programmed to your VIN, making it plug-and-play. |
| Used OEM | $35 - $100 | Cheapest hardware option, but requires separate programming. |
| Shop Labor (Replacement) | $100 - $150 | Physical installation is quick, typically under an hour. |
| Shop Labor (Programming) | $150 - $375 | Cost for a dealer or independent shop to sync the module to your car. |
Frequently Asked Questions (FAQ)
Does a replacement ECM for a 1999 Galant need to be programmed?
Yes, absolutely. Due to the factory immobilizer system, a replacement ECM must be programmed to your vehicle's VIN and keys to allow the engine to start. The only exceptions are pre-programmed units from mail-in services or installing a complete matched set (ECM, immobilizer, key) from a donor car.
Why won't my car start after swapping the ECM?
The most likely reason is an immobilizer mismatch. The replacement ECM is still coded to the donor vehicle, and your car's security system is preventing it from starting. The security light on your dashboard may be flashing. 🎬 Watch this video on fixing ECM immobilizer lockouts The module needs to be professionally programmed to your car.
Can I program the ECM myself?
No, not without very specialized and expensive tools like the dealer's MUT-II/MUT-III scanner or professional-grade aftermarket systems. A simple OBD-II code reader cannot perform this function. For most owners, this is a job for a dealer, a specialized locksmith, or a mail-in cloning service.
What is the difference between a California and Federal emissions ECM?
A California emissions (CARB) ECM has different software programming than a Federal (EPA) version to meet stricter pollution standards. They are generally not interchangeable. You must use an ECM that matches your vehicle's original emissions specification, which can be found on the VECI label under the hood.
Helpful Videos
Technical Specifications
OEM Part Numbers: E2T67683 E2T70173 E2T75187 MD355244 MD355245 MD355246 MD355248 MD355249 MD369101 MR482502 E2T70271
Module programming required for immobilizer synchronization. Variations exist for 2.4L and V6 engines, Manual and Automatic transmissions, and Federal and California emissions.
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The information in this article is provided for general reference and educational purposes only. Vehicle specifications, procedures, and part compatibility can vary by production date, trim level, and region. Always consult your vehicle's factory service manual and verify part numbers before purchasing or performing repairs. Safety-critical components such as airbags, seat belts, and braking systems should be installed by a qualified professional.
- Mitsubishi Galant:
- 🎬 Helpful Videos
- 🛍️ Shop This Part
- Critical: Immobilizer Programming is Required
- Symptoms of a Failing 1999 Galant ECM
- Buying a Used 1999 Galant ECM: A Buyer's Guide
- How to Verify Compatibility
- Physical Inspection
- Known Issues, Recalls, and TSBs
- Cost Breakdown
- Frequently Asked Questions (FAQ)
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