Sudden deactivation of Adaptive Cruise Control (ACC) and Active Emergency Braking System (AEBS).

Renault electrical systems are highly sensitive to voltage drops. A dying 12V battery or failing alternator can drop voltage low enough during startup to force multiplexed networks to lose sync, causing false-positive active fault codes. Step-by-Step Diagnostic and Repair Protocol

The is not a luxury experience. It is a raw, sometimes harsh, but incredibly rewarding performance upgrade for one of the greatest front-wheel-drive chassis ever made.

He traced the wiring, his fingers brushing against scorching metal. He found it: a wire harness, brittle from years of heat cycles, had finally melted against the exhaust shield. The short-circuit was feeding bad data to the ECU, making the car think the brakes were being slammed while the throttle was wide open. It was a digital fever.

| Feature | Type A: Software / ADAS Issue | Type B: Transmission / Hardware Issue | | :--- | :--- | :--- | | | Mégane IV, Scénic IV, Talisman, Koleos (2015+) | Mégane III, Fluence, older CVT models (2010-2014) | | Warning Lights | "Check ABS", "Check ESC", "Check Hill Start Assist", "Emergency Brake Assist deactivated" | "Check Gearbox" or "Check Injection" (usually alone, not with ABS lights) | | Cruise Control | Adaptive Cruise Control (ACC) stops working or is erratic | Standard Cruise Control usually works fine | | Transmission Feel | Gear changes are smooth; car drives normally | Harsh shifting, slipping, whining noise (CVT), or refusal to move | | Triggers | Appears after ~10–30 meters of driving or after a battery change | Appears immediately on start-up or when gearbox is under load | | Weather Effect | Often appears only in rain or cold weather (a key clue) | No change; happens regardless of weather |

Here is a specific gremlin. A DF357 that is "hot" (thermally) often refuses to restart. This is because the Lucas injection pump internal clearances expand, dropping rail pressure. If you shut off a hot DF357 for fuel, you might be waiting 45 minutes to restart.

If you are using Renault-specific diagnostic software like or CLIP , you will usually see these sub-codes populate alongside DF357, helping pinpoint which wheel or circuit is causing the loss of communication. How to Diagnose and Fix the DF357 Code

The . When this code triggers, it typically forces the vehicle into a defensive electronic mode, turning off critical driver-assist features like electronic stability control (ESC), active emergency braking, and adaptive cruise control. The keyword suffix " hot " highlights a highly frustrating characteristic of this fault: it frequently appears as an intermittent issue that triggers only after the vehicle warms up or during long summer drives.

One of the most persistent stories in the Renault community is the "Battery myth." Because DF357 is often accompanied by code , many mechanics instantly claim the battery is dead.