DF015

Code

RENAULT D

-> P0657 - main relay control circuit

Brand: RENAULT

Type: D

Views: UK: 2 EN: 9 RU: 6

AI status

Completed

ready

Completed 100%

Page language: EN

Causes

Blown or corroded fuse supplying the main relay circuit
Failed main (power/ECU) relay or poor relay seating/contacts
Broken, shorted or high-resistance wiring between battery, relay, and ECU
Poor or corroded ground(s) in relay/ECU circuit
Faulty ECU/ECM driver transistor controlling the relay
Aftermarket immobiliser/alarm or wiring modifications interfering with relay

Symptoms

Engine will not crank or starts then stalls (depending on relay function)
No power to ECU, fuel pump, injectors or ignition coils when relay not energized
Malfunction Indicator Lamp (MIL) or warning lights illuminated
Intermittent loss of electrical systems tied to main relay
Possible loss of communication with ECU on diagnostic tool

What to check

Read and record stored DTCs and freeze frame data with a scan tool
Check battery voltage (engine off and key ON) and battery terminal condition
Visually inspect fuses, relay, fusebox and wiring for corrosion, damage or melting
Swap main relay with a known-good identical relay if available (observe operation)
Probe relay socket: confirm permanent +12V supply and ECU control signal presence
Check ground continuity from relay ground pin to chassis/negative battery

Signal parameters

Battery supply to relay: approx. 11.5–14.5 V with key ON (vehicle-specific)
Relay coil/control: typically ECU provides a switching-to-ground control — expect change between ~0 V (ON) and open/high (OFF)
Relay coil resistance: manufacturer-specific; commonly tens to a few hundred ohms (measure and compare to known-good relay)
No-load current to ECU/fuse outputs: presence of expected terminal voltages when relay energized

Diagnostic algorithm

With scan tool, confirm DF015/P0657 and note any concurrent codes (immobiliser, power supply, communication).
Check battery voltage and battery terminal condition. Charge or replace battery if low.
Visually inspect and test fuses supplying the main relay circuit; replace suspect fuses.
Locate main relay and inspect connectors for corrosion, bent pins or water ingress.
With ignition ON (engine off), measure permanent +12V at the relay supply terminal. If missing, trace back to fuse/battery.
Operate or swap the relay: if swapping restores operation, replace the relay.
Probe relay control terminal while cranking/key ON: verify ECU control toggles the terminal to ground (or as specified). If control signal missing or stuck, backprobe wiring to ECU for continuity and shorts to battery.
Check ground continuity from relay ground to battery negative. Repair any high-resistance or open ground.
If wiring, fuses and relay are good but control signal is abnormal, suspect ECU driver fault or immobiliser inhibiting relay — verify immobiliser status and consider ECU bench/repair diagnostics.
After repairs, clear codes and perform functional test (multiple key cycles and a road/test start) to confirm fault does not return.

Likely causes

Failed main relay
Open or short in relay control wire to ECU
Weak/low battery or poor battery terminal connection affecting relay supply
Corroded connector at relay or ECU causing intermittent contact

Fault status

⚠️ Status

DF015 / P0657 — Main relay control circuit fault detected. Possible open/short in control circuit, failed relay, blown fuse, poor ground, or ECU driver issue. Intermittent or no power to systems when relay not functioning.

🟡 Repair difficulty: Medium

⏱️ Diagnostic time: 0.5-1.5 hours

Similar codes

Your experience will help others

+100 karma for a short comment :)

Was this AI description helpful?

Your feedback helps improve AI descriptions.

👍 Like 0 👎 Dislike 0

Send to email

DF015 — -> P0657 - main relay control circuit