2004 Scion xA ECM: Your Guide to Part Numbers, Immobilizer Resets, and Replacement

Compatibility Warning: Manual Transmission Only

Symptoms of a Failing ECM

A failing ECM can cause a variety of confusing symptoms. Because the ECM controls so many different systems, its failure can sometimes be misdiagnosed as a bad sensor or other component. Here are the most common signs that your ECM may be the problem:

• Check Engine Light: This is the most obvious sign. The light may be on constantly, or it may come on intermittently. Specific codes pointing to internal ECM failure are a strong indicator.
• Engine Will Not Start: The ECM controls the fuel and spark required for startup. If it fails completely, the engine may crank but will not start.
• Engine Stalling or Misfiring: The engine may stall unexpectedly while driving or idle very roughly. This can happen if the ECM is not correctly managing the air-fuel mixture or ignition timing.
• Poor Engine Performance: You might notice a sudden loss of power, sluggish acceleration, or hesitation.
• Decreased Fuel Economy: If the ECM isn't managing the engine efficiently, you'll likely see a noticeable drop in your gas mileage.
• Communication-Related OBD-II Codes: While many codes can point to a bad ECM, some are more specific. Look for codes in the P0600-P0607 range, which indicate internal control module problems, or U-series codes like U0100, which mean 'Lost Communication With ECM/PCM'.

Programming and Immobilizer Reset: The Critical Step

You cannot simply swap the ECM in a 2004 Scion xA and expect it to work. The vehicle is equipped with a factory anti-theft system, also known as an immobilizer. The immobilizer system uses a transponder chip in your key that 'talks' to the car. The Engine Control Module is a key part of this system. When you install a different ECM, the car will not recognize it and will prevent the engine from starting. This is not a defect; it's a security feature.

To get the car to start with a replacement ECM, you must sync the new module to the vehicle's immobilizer system. You have three main options to do this:

Option 1: Buy a Pre-Programmed Unit with a Reset Tool

Many online vendors sell remanufactured ECMs that come pre-programmed to your vehicle's VIN. When you order, you provide your VIN, and they flash the module before shipping it. These units often come with a small OBD-II reset tool. The process is straightforward:

1. Install the new, pre-programmed ECM.
2. Plug the reset tool into the OBD-II port under the dashboard.
3. Turn the ignition key to the 'ON' position (do not start the engine) for about 30 minutes.
4. Turn the ignition off, remove the tool, and then start the car.

This is often the easiest method for DIY mechanics.

Option 2: The DIY 'Paperclip' Method

For a used ECM that has not been pre-programmed, it is possible to perform the immobilizer sync yourself. This procedure forces the car's transponder ECU and the engine ECM to communicate and re-sync. It is often called the 'paperclip method' because it involves shorting two pins in the OBD-II port.

1. Install the replacement ECM.
2. Using a jumper wire or a paperclip, connect pin 4 and pin 13 of the OBD-II port. Pin 4 is the 4th pin from the left on the top row. Pin 13 is the 5th pin from the left on the bottom row (or 4th from the right).
3. With the pins connected, turn the ignition key to the 'ON' position for 30-40 minutes. The security light on the dash may flash. Do not turn the engine on.
4. After 30-40 minutes, turn the ignition 'OFF' and remove the jumper wire.
5. The vehicle should now start.

Option 3: Professional Programming

A dealership or a well-equipped independent auto shop can program the replacement ECM for you. They use a professional scan tool with software like Toyota's Techstream. A mobile automotive locksmith may also be able to perform this service. This is the most expensive option but requires the least amount of work on your part.

Buying a Used Engine Control Module (ECM)

A used OEM ECM is a cost-effective and reliable option, as long as you know what to look for. Aftermarket ECMs for this vehicle are not common, and a recycled original part is often the best choice.

• Match the Part Number Exactly: The most important step is to match the OEM part number on your original ECM. For a 2004 Scion xA with a manual transmission, this is typically 89666-52300. Other compatible numbers may include 212000-0680, 212000-0690, or 89666-52310. Do not install an ECM with a different part number, especially one from an automatic transmission model.
• Physical Inspection: When you receive the used ECM, inspect it carefully. Look for any signs of corrosion on the pins or case, which could indicate water damage. Ensure none of the connector pins are bent or broken.
• Understand Programming is Required: Remember that a used ECM from another vehicle is not plug-and-play. You MUST perform one of the immobilizer reset procedures described above. Factor this into your decision and cost.

Known Issues, Recalls, and Technical Service Bulletins (TSBs)

There are no known recalls or TSBs from Toyota or the NHTSA specifically for the Engine Control Module on the 2004 Scion xA.

However, there is a very important safety recall for the Airbag Control Module (SRS ECU). This is a separate computer that controls the airbags.

• NHTSA Recall ID: 18V776
• The Problem: The airbag control module can experience an internal short circuit. This can cause the airbags and seatbelt pretensioners to either become disabled entirely (and not work in a crash) or deploy unexpectedly while driving.
• The Fix: Dealers will inspect the airbag control module and, if it is an affected part, replace it for free.

It is crucial to distinguish between the Engine Control Module (ECM) and the Airbag Control Module (SRS ECU). You can check if your vehicle is affected by this recall on the NHTSA website.

Replacement Overview

Replacing the ECM is mechanically simple. The difficulty comes from the required programming.

• Difficulty: 2/5 (physical replacement), 4/5 (including programming)
• Location: The ECM is located behind the glove compartment.
• Basic Steps:
  1. Disconnect the negative battery terminal.
  2. Open and remove the glove compartment by squeezing the sides.
  3. Remove the two 10mm bolts holding the ECM bracket in place.
  4. Unplug the four wiring harness connectors from the ECM. The connectors have levers that need to be released to unplug them.
  5. Swap the mounting brackets from the old ECM to the new one.
  6. Installation is the reverse of removal. After installation, you must perform the immobilizer reset procedure.

Cost Breakdown

Prices can vary, but here is a general estimate for replacing the ECM in a 2004 Scion xA.

Frequently Asked Questions (FAQ)