P1018

Code

DACIA P — Powertrain

Engine coolant blower motor relay, high speed - circuit malfunction

Brand: DACIA

Type: P — Powertrain

Views: UK: 1 EN: 3 RU: 2

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Page language: EN

Causes

Failed or sticking high-speed fan relay
Blown fuse for fan/relay circuit
Open, short or high-resistance wiring between control module, relay and fan
Corroded/loose connector at relay or fan
Faulty engine cooling fan motor (excessive current draw or open)
Faulty control module output (ECM/BCM) or poor ground at module

Symptoms

Radiator cooling fan does not run on high speed when commanded
Engine temperature rises at idle or in slow traffic; possible overheating
Reduced A/C cooling effectiveness at low vehicle speeds
Check Engine light or fault stored in control module
Fan may run on low speed but not on high, or not at all

What to check

Read and record freeze-frame/related codes; verify P1018 is current or historic
Visual inspection of fan relay, fuses, fuse box and wiring for damage or corrosion
Check connector pins for corrosion, looseness or water
Swap the suspected relay with a known-good same-type relay (if available)
Measure battery voltage at fuse/relay input with ignition ON
Measure voltage at fan motor connector while commanding high speed (or with A/C on/engine hot)

Signal parameters

Battery voltage at relay/fuse: ~12.0–14.5 V (should be near battery voltage with ignition ON/engine running)
Relay control signal from module: typically a switched ground or +12 V when commanded (verify on vehicle wiring diagram)
Relay coil resistance (typical automotive relay): ~50–200 ohms (varies by relay type) — consult parts data
Expected fan current draw: varies by vehicle and fan size (commonly 5–40 A); a rapid absence of expected current indicates open circuit
Voltage at fan motor terminal when commanded high: close to battery voltage (minus wiring drop); significantly lower indicates high resistance or open

Diagnostic algorithm

Retrieve and record all stored codes and freeze-frame data. Confirm current/frequent occurrence.
Inspect fuses related to cooling fan and associated packaging for damage. Replace if blown and note if it reoccurs.
Visually inspect the high-speed relay and its socket. Check for melted plastic, corrosion or water intrusion.
If accessible, swap the high-speed relay with an identical spare relay (e.g., horn or other identical relay) to see if fan operation changes.
With the engine running and A/C on (or with the module commanded to run fan high), measure voltage at the relay output and at the fan motor connector. Compare to battery voltage.
Check the relay control circuit at the module while commanding high speed: verify the module provides the expected switch (ground or +12 V) to energize the relay coil. Use wiring diagram to identify pins.
Check continuity and resistance of wiring between module → relay → fan. Look for opens, shorts to battery/ground, or high resistance.
Bench-test the fan motor by supplying 12 V directly to the motor terminals to confirm motor spins and to measure current draw. If motor draws excessive current or does not run, replace motor.
Check ground connections for proper continuity and clean/repair if corroded or loose.
Repair or replace faulty wiring, connector, relay, or fan motor as indicated. Clear codes and perform a road/idle test to verify proper fan operation and absence of code.

Likely causes

Failed high-speed fan relay
Blown or corroded fuse or relay connector
Damaged wiring (open/short) to fan motor or relay
Excessive current draw from a failing fan motor
Poor ground at fan motor or control module

Fault status

⚠️ Status

P1018 — Engine cooling fan high-speed circuit malfunction. Control module commanded the high-speed fan relay but detected incorrect circuit behavior (open, short, excessive resistance, or relay failure).

🟡 Repair difficulty: Medium

⏱️ Diagnostic time: 0.5–2.0 hours

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P1018 — Engine coolant blower motor relay, high speed - circuit malfunction