Code
P1109
ALFA ROMEO
P — Powertrain
Electric fan assembly 2 fault
Views:
UK: 5
EN: 10
RU: 10
AI status
Completed
Completed
100%
Causes
- Blown fuse for fan circuit
- Faulty cooling fan relay or driver
- Open/shorted wiring or corroded connector at fan 2
- Failed fan motor or internal resistance change
- Mechanical binding (obstruction or seized fan)
- Faulty engine control module (ECU) or fan driver output
Symptoms
- Cooling fan 2 does not operate when expected
- Engine runs hotter than normal or overheats in traffic
- Reduced air conditioning cooling performance
- Cooling fan runs continuously or only on high speed
- Malfunction Indicator Lamp (MIL) or message on dash in some models
- Possible unusual noise from fan assembly (bearing/motor)
What to check
- Use a diagnostic scanner to read freeze frame, pending counts and live data for fan commands and statuses
- Visually inspect fuses and relays related to radiator/cooling fans
- Inspect fan 2 connector for corrosion, bent pins, or water ingress
- Check wiring for chafing, breaks, or short to ground/power between fan connector and ECU/relay
- Command fan 2 ON/OFF with scan tool and observe operation (keep hands clear of moving parts)
- Measure battery voltage at fan connector with fan commanded ON
Signal parameters
- Battery supply voltage at fan connector: ≈ 12–14.5 V when engine running
- Control signal type: switched battery feed or PWM from ECU (check service data)
- PWM frequency and duty cycle (if PWM-controlled): typical tens to hundreds Hz; duty varies with demand
- Motor coil resistance: compare to spec (low ohms typical; very high or open indicates failure)
- Current draw at full speed: expected amps per vehicle spec (excessive draw indicates mechanical/electrical fault)
- Engine coolant temperature where fan should activate (°C) and AC demand status
Diagnostic algorithm
- Record freeze frame and live data with scan tool. Note whether fan 2 is commanded ON by the ECU (command signal/state) and whether the fan actually spins.
- Visual inspection: check fuses, relays, connectors and wiring for damage or corrosion. Repair obvious faults before further testing.
- With ignition ON (engine off) or engine running as manufacturer instructs, command fan 2 ON via scan tool and observe. Keep clear of moving parts.
- If fan does not run when commanded, measure voltage at fan power pin with command active. If battery voltage present, suspect fan motor. If no voltage, continue to trace power/driver.
- Measure continuity/ground at fan ground pin. Repair poor ground connections.
- Disconnect fan connector and measure motor resistance across motor terminals. Open or very high resistance indicates motor failure. Very low resistance with no rotation may indicate mechanical seizure.
- If wiring/power/ground good and motor appears functional, test fan motor by applying fused direct 12 V supply briefly to confirm operation (bench test or vehicle with caution).
- If motor works with direct supply but not with ECU command, test/replace relay or check ECU output/driver circuit. Use oscilloscope to check PWM signal if applicable.
- Repair or replace failed wiring, connector, relay, fuse, or fan assembly as required. Replace components with OEM-correct parts.
- Clear codes, retest with scan tool and road test to verify cooling performance and that P1109 does not return.
Likely causes
- Failed fan motor (most common)
- Damaged connector or wiring to fan assembly
- Blown fuse or faulty relay
- Corroded ground or poor power supply
- ECU/fan driver fault (less common)
Fault status
Status
ECU stored fault for Cooling Fan 2 circuit. May set MIL depending on vehicle configuration. Fault can be pending or confirmed; cooling performance may be reduced and overheating risk increased until addressed.
Repair difficulty: Medium
Diagnostic time: 1.0-2.5 hours
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