Renault DF357

The Renault DF357 is a diesel engine model developed by Renault’s industrial powertrain division for heavy-duty applications such as trucks, buses, and stationary machinery. Characterized by its robust construction and focus on fuel efficiency, the DF357 reflects Renault’s engineering priorities of durability, low operating cost, and ease of maintenance for commercial operators.

A. Switch and Control Unit Issues (Most Common)

Stuck Buttons: The buttons on the steering wheel or steering column stalk may be physically stuck or have debris lodged under them.
Contact Wear: The internal contacts of the cruise control switch have worn out, sending erratic "on/off" signals simultaneously to the ECU.
Rotary Switch Fault: The main selector switch (Off/Cruise/Limiter) may have an open circuit or poor connection.

4. Potential Causes

The root cause of DF357 can range from simple user error to component failure:

3. The Causes (The "Full Story" of Failure)

There isn't usually one single cause for DF357. It is a "communication" error, meaning the fault could be at either end of the line or the line itself.

A. The "Usual Suspect": The ABS/ESP Pump Module This is the most common cause in older Renaults (Megane, Scenic, Laguna, Clio). The ABS/ESP pump unit contains a control module. These are known to suffer from:

Internal Electronic Failure: Solder joints inside the unit crack or burn out due to heat and vibration.
Water Ingress: The ABS pump is often located low in the engine bay or near the wheel arch. Water and road salt can enter the connectors, causing corrosion on the pins. This interrupts the signal.

B. Wiring Issues (The CAN Bus) The signal travels via the CAN Bus (Controller Area Network) wiring.

Chafed Wires: Wires running near the chassis can rub against metal, wearing away the insulation and causing a short circuit.
Damaged Connectors: If the connector at the ABS pump or the Engine ECU is loose or has bent pins, the signal will drop out.

C. Engine ECU Issues While less common, the Engine ECU itself could be faulty. If the Engine ECU is "deaf" to the torque reduction requests from the ESP, DF357 will be stored.

1. The Meaning of DF357

In Renault’s specific diagnostic language, DF357 stands for: "Multiplexed signal for engine torque request."

To understand this, you have to understand how modern cars work. The ESP computer (the computer that handles stability and traction control) and the Engine ECU (the computer that runs the engine) are constantly talking to each other.

The conversation: When the ESP detects the car is sliding, it sends a "message" (signal) to the Engine ECU saying, "Reduce engine power immediately so the wheels stop spinning."
The fault: Code DF357 means that conversation has broken down. The ESP computer sent the signal to cut torque, but the Engine ECU either didn't receive it, didn't understand it, or failed to execute the command.

In simple terms: The traction control system cannot communicate with the engine to reduce power.

6. Where You Might See It Today

The DF357 is found in historic F1 cars, particularly the Lola LC91 and possibly some test mules.
It is sometimes displayed at historic motorsport events (e.g., Goodwood Festival of Speed) or in museums (Renault Collection, Lola Heritage).

The Renault DF357: The Forgotten Heart of a Golden Era

In the pantheon of great Formula 1 engines, names like Ferrari’s Tipo 021, Honda’s RA168E, and Ford’s Cosworth DFV reign supreme. Yet, lurking in the shadow of the turbo era is a remarkable piece of engineering that rarely gets its due: the Renault DF357.

To understand the DF357, one must first understand the chaos of the mid-1980s. This was the peak of Formula 1’s "turbo wars," where qualifying boost pressures approached 5.5 bar and engines produced north of 1,300 horsepower in short bursts. Renault had pioneered turbocharging in F1 with the RS01 in 1977, but by 1983, they were playing catch-up to BMW, TAG-Porsche, and Ferrari.

The DF357 was Renault’s answer to that pressure—the final evolution of the 1.5-liter V6 turbo before regulations changed and the manufacturer withdrew its factory team at the end of 1985.

Performance and fuel efficiency

Engines in the DF357 family are tuned to deliver strong low-end torque, which is essential for hauling and urban stop-start duty. Turbocharging and intermediate-pressure fuel injection systems improve combustion efficiency and responsiveness. Emphasis on fuel economy is achieved through precise fuel metering, efficient combustion chamber design, and modern turbocharger matching, allowing operators to reduce fuel costs over the vehicle’s lifetime while retaining adequate power for demanding conditions.

B. Multiplex / Network Issues

CAN Bus Errors: Interference or a break in the CAN (Controller Area Network) wiring between the steering wheel controls and the ECU.
Software Incoherence: A mismatch in the software configuration between the instrument panel and the injection ECU (common after battery replacements or jump-starting).

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