Porsche 964 Motronic control unit ECU 96461812400 Bosch 0261

964.618.124.00 is the standard Motronic engine management computer for the Porsche 964 Carrera 2 and Carrera 4 models (1989–1994) featuring the M64/01 engine.

The full Bosch part number typically associated with this unit is 0 261 200 473.

Technical Roles

This unit is the primary “brain” for the 3.6L flat-six. Unlike earlier Porsches that split fuel and ignition, this Motronic system integrates both into a single processor to manage:

• Sequential Fuel Injection: Precise timing for each cylinder’s injector.

• Dual Ignition System: Managing the two spark plugs per cylinder, which is a hallmark of the 964 engine.

• Idle Stabilization: Controlling the Idle Control Valve (ICV) to maintain a steady $880 \pm 40 \text{ RPM}$.

• Knock Control: Utilizing two knock sensors to retard timing if low-quality fuel is detected.

Common Failure Points

These units are now over 30 years old and are prone to specific electronic aging issues:

• DME Relay Issues: While the relay is external, a faulty relay can cause the ECU to “spike” or lose power intermittently.

• Leaking Capacitors: The electrolytic capacitors inside the 0261 series often leak over time, causing acidic damage to the circuit board traces.

• Solder Joint Fatigue: Vibration and thermal expansion can crack the solder joints on the main header pins.

• Corroded Ground Traces: If the chassis grounds are poor, the ECU can attempt to ground itself through the internal board, causing “burnt” traces.

Quick Reference Specs

Performance Upgrades

Because this unit uses a socketed EPROM chip, it is very common to find these with aftermarket tuning. A performance chip in a 964 ECU typically:

• Removes the “flat spot” in the $2,500\text{ to }3,000 \text{ RPM}$ range.

• Increases the rev limit slightly (standard is $6,700 \text{ RPM}$).

• Optimizes timing for $93+$ octane fuel, resulting in roughly $+12\text{ to }15 \text{ hp}$.

Maintenance Tip: If your 964 is experiencing a “no-start” condition or random stalling, always check the DME Relay (993.615.227.01) first before condemning the Motronic unit. It is a much cheaper and more common point of failure.