2019 Subaru Impreza ECM: Recall, Programming, and Failure Guide

The Engine Control Module (ECM) in the 2019 Subaru Impreza is a critical component, but it's also the subject of a major recall and can be complex to replace due to programming requirements. Understanding these key issues is essential before diagnosing or purchasing a replacement.

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

Major Recall: Risk of Stalling (NHTSA #19V743000 / Subaru #WUQ-02, WRE-21)

A significant recall was issued for 2017-2019 Impreza models due to a serious flaw in the ECM's software. The original programming could allow the ECM to continue powering the ignition coils even after the engine was turned off. This could lead to a short circuit in an ignition coil and blow a fuse.

If this short circuit occurred while driving, the engine could stall without warning, increasing the risk of a crash. The fix involves a Subaru dealership updating the ECM software. In cases where an ignition coil was found to be damaged, the dealer would also replace the coils and potentially the front exhaust pipe, all free of charge. This recall was later updated under campaign WRE-21, which included all vehicles previously repaired under the first recall, as the initial fix was found to be insufficient.

Symptoms of a Failing ECM

A faulty ECM can cause a wide range of problems, from subtle to severe. Many of these symptoms can also be caused by simpler issues, so a thorough diagnosis is key.

• Check Engine Light: This is often the first and most obvious sign. The light may be accompanied by codes related to internal module failure or sensor circuits.
• Engine Stalling or Misfiring: The engine may stall unexpectedly, run rough, or misfire. This was a primary symptom of the major ECM recall.
• No-Start or No-Crank Condition: The engine may refuse to start at all. You might hear a click but no crank, or the engine may crank but never fire up. This can be due to the ECM not commanding the starter or fuel system, or because of an immobilizer conflict.
• Poor Engine Performance: You may notice a sudden drop in fuel economy, hesitation during acceleration, or a general lack of power.
• Irregular Shifting: Since the ECM communicates with the transmission controller, a faulty ECM can sometimes lead to harsh or erratic shifting in CVT models.

Common Diagnostic Trouble Codes (OBD-II)

While many codes can be triggered by a failing ECM, codes in the P06xx range point specifically to the module itself or its internal circuits.

• P0606 (Control Module Processor Fault): This is a generic code indicating an internal error within the ECM. However, it can sometimes be falsely triggered by poor power/ground connections, a weak battery, or a shorted external sensor. Always check these external factors before condemning the ECM.
🎬 Watch: How to properly diagnose a P0606 processor error.
• P0601 (Internal Control Module Memory Check Sum Error): This code indicates a problem with the ECM's memory and is a strong indicator of module failure.
• P0604 (Internal Control Module Random Access Memory (RAM) Error): Points to a failure of the ECM's internal RAM.
• P0605 (Internal Control Module Read Only Memory (ROM) Error): Points to a failure of the ECM's internal ROM.

Programming and Immobilizer Requirements

A replacement ECM for a 2019 Impreza is NOT plug-and-play. It must be programmed to the vehicle's immobilizer system to allow the engine to start.

Replacement Options:

• New OEM Module: When a brand-new ECM is installed by a dealer, it enters an "automatic registration mode" and can be programmed to learn the vehicle's existing keys using dealer-level scan tools.
🎬 Watch: A demonstration of programming a new Subaru ECM.
• Used OEM Module (Cloning): If your original ECM is still able to communicate, a specialist can perform a "cloning" service. This involves reading the VIN and immobilizer data from your original module and writing it directly onto the used replacement. The vehicle will not know the difference, and no additional key programming is needed.
• Used OEM Module (IMMO OFF): If your original ECM is dead and cannot be read (e.g., due to water damage or internal failure), cloning is not possible. In this case, a specialist can perform an "IMMO OFF" service on the replacement module. This disables the immobilizer function within the ECM, allowing the engine to start. The vehicle's VIN must still be programmed into the module for full functionality.

Buying a Used Engine Control Module (ECM)

Purchasing a used OEM ECM is a cost-effective solution, but careful verification is crucial. Given the programming requirements, a cheap, incorrect part can lead to expensive and frustrating problems.

Inspection and Verification:

• Match the Part Number Exactly: The part number on the replacement ECM must be an exact match or a direct, officially superseded number. The correct part numbers for the 2019 Impreza with an Automatic (CVT) transmission are in the 22765AM67x series (e.g., 22765AM67A, 22765AM67B, etc.). Do not use a module for a manual transmission (22765AM65x series).
• Check for Physical Damage: Inspect the module for any signs of damage. Look for bent pins on the connectors, cracks in the casing, or signs of being pried open.
• Look for Water Damage: The ECM is located in the passenger footwell, an area susceptible to moisture. Look for any white or greenish corrosion on the casing or inside the connector ports. A water-damaged ECM should be avoided as its internal components may be compromised.
• Source from a Reputable Seller: Buy from a supplier that offers a warranty and has a good return policy. This protects you if you receive a non-functional or incorrect part.

Cost Breakdown

The cost to get your vehicle running again can vary significantly based on the parts and labor you choose.

Replacement Overview

The ECM is located in the passenger-side footwell. While physical replacement is straightforward for a DIY mechanic, remember that programming is required afterward.

1. Disconnect the Battery: Always disconnect the negative battery terminal before working on any electronic components.
2. Access the Footwell: Remove the passenger-side plastic door sill plate and kick panel.
3. Pull Back the Carpet: Peel the carpet back from the firewall to expose a metal cover plate.
4. Remove the Cover Plate: The plate is typically held on by several 10mm bolts and/or nuts. Remove them and take the cover off.
🎬 See this walkthrough for locating and removing the module.
5. Unbolt the ECM: The ECM itself is secured with two 10mm bolts. Remove these.
6. Disconnect Harnesses: Carefully press the release tabs on the large wiring connectors and pull them straight out from the ECM. Do not force them.
7. Install the New ECM: Installation is the reverse of removal. Ensure all wiring connectors 'click' firmly into place to guarantee a good connection.

Frequently Asked Questions (FAQ)