2010 Audi S4 & S5 3.0T Engine Control Module: A Guide to Failure, Replacement, and Programming

Symptoms of a Failing ECM

A failing Engine Control Module can manifest in various ways, often mimicking other component failures. Diagnosing a bad ECM should be a process of elimination after checking related sensors and wiring. Here are the most common signs of a faulty ECM in the 2010 Audi S4 and S5:

• Check Engine Light and EPC Light: A persistent Check Engine Light is a primary indicator. Often, the Electronic Power Control (EPC) light will also illuminate, which typically puts the car into a reduced-power "limp mode."
• No-Start or Hard Starting: The engine may crank but fail to start, or it may take multiple attempts to fire up. This can happen if the ECM is not correctly signaling the fuel injectors or ignition coils.
• Engine Stalling or Misfiring: The engine may stall unexpectedly, run rough, or misfire. This can feel like a bad fuel pump or ignition coil, but it can originate from the ECM itself.
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• Poor Performance and Fuel Economy: A noticeable drop in power, hesitation during acceleration, and a sudden decrease in fuel efficiency can point to an ECM that is no longer calculating the air-fuel mixture correctly.
• Communication Errors: A professional scan tool may be unable to communicate with the ECM. You might also see a cluster of unrelated fault codes, which can indicate an internal processing error in the module.
• Transmission Shifting Problems: The ECM communicates with the transmission control module. A faulty ECM can lead to harsh shifting or the transmission getting stuck in one gear.

Common OBD-II Codes Associated with ECM Failure

While many codes can be related, these are strongly indicative of an internal ECM fault:

• P0601: Internal Control Module Memory Check Sum Error
• P0606: ECM/PCM Processor Fault
• P1640 / 18048: Internal Control Module - EEPROM error

Known Issues, TSBs, and Recalls

While there are no specific recalls for the ECM itself on the 2010 Audi S4 and S5, several Technical Service Bulletins (TSBs) involve software updates to the ECM to fix other issues. If you are replacing an ECM, it's crucial to ensure it has the latest software version.

• TSB 01-16-68 (2040491): Addresses a false "Coolant System: Fault" warning caused by overly sensitive diagnostic software. The fix is an ECM software update.
• TSB 17-16-75 (2038119): Pertains to a false "Oil minimum warning" message. While the primary fix is a new oil level sensor, the procedure notes adapting the new sensor in the instrument cluster, which communicates through the ECM.
• TSB 21-18-10 (2039995): For DTCs P0491 and P0492 related to the secondary air injection system, which is controlled by the ECM. The issue is carbon buildup, not an ECM fault, but it highlights how other system faults can appear to be computer-related.

Buying a Used Engine Control Module

Purchasing a used ECM is a cost-effective option, but it requires careful attention to detail to avoid compatibility issues. This is not a simple plug-and-play part.

1. Match the Part Number Exactly

The most critical step is to match the OEM part number from your original ECM. The primary part numbers for the 2010 S4 and S5 3.0T are:

• 8K0907551A
• 8K0907551B
• 8K0907551D

The letter at the end signifies a hardware or software revision. While later revisions (like 'D') may be compatible with cars that originally had an 'A' or 'B' version, this must be verified by a professional. It is always safest to match the full part number. Part number 8K0990990A is also listed, which typically denotes a remanufactured unit from Audi.

2. Vehicle Compatibility

This ECM is specific to the 3.0L TFSI supercharged V6 engine.

• 2010 Audi S4: Fits all models, as this was the only engine available.
• 2010-2012 Audi S5: This ECM fits Convertible (Cabriolet) models only. The 2010 S5 Coupe used a 4.2L V8 engine with a different ECM.

3. Physical Inspection

When you receive the used ECM, inspect it carefully. Look for:

• No Corrosion: Check the connector pins for any signs of green or white corrosion, which indicates water damage.
• Intact Case: Ensure the housing has not been pried open or damaged.
• Clean Connectors: The ports where the wiring harness plugs in should be clean and free of debris or bent pins.

4. Plan for Programming

The biggest hurdle with a used ECM is programming. You have two main options:

• Dealer/Specialist Programming: An Audi dealer or a qualified independent shop with ODIS (Official Diagnostic Information System) software can adapt the used module to your car. This process involves removing "Component Protection," an anti-theft feature that locks the module to the original vehicle. Be aware that many dealers are unwilling or unable to program used modules.
• Cloning Service: This is often the best route for a used part. You send your original ECM and the replacement used ECM to a specialist service. They will transfer all the critical data—including VIN, immobilizer information, and software coding—from your old module to the replacement. The result is a plug-and-play unit that does not require a trip to the dealer. This is only possible if your original ECM can still be read.

Replacement Cost Breakdown

The cost of replacing the ECM can vary significantly based on the path you choose. Programming is a mandatory additional cost unless you use a cloning service that provides a plug-and-play unit.

Frequently Asked Questions (FAQ)