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Home / DTC / P1473 — Fan Secondary High With Fan(s) Off

P1473 — Fan Secondary High With Fan(s) Off

Detailed page for trouble code P1473.

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P1473

Other P — Powertrain

Fan Secondary High With Fan(s) Off

Brand: Other
Type: P — Powertrain
Views: UK: 28 EN: 74 RU: 34
AI status
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ready
Completed 100%
Page language: EN

Causes

  • Stuck or welded relay contacts supplying power to the fan circuit
  • Short to battery voltage on fan power or control wiring
  • Failed fan control module (stuck MOSFET/transistor) internally shorted on
  • Incorrect or spurious tach/speed signal from fan motor or sensor
  • Aftermarket accessory or wiring backfeeding the fan circuit
  • Faulty PCM/BCM output or software fault (less common)

Symptoms

  • Cooling fan(s) run at high speed or appear powered when fan command is OFF
  • Battery drain or parasitic draw with ignition off
  • Loud fan noise when vehicle is parked or key off
  • Cooling system behavior may be normal or overactive (fans running unexpectedly)
  • Related cooling fan DTCs or multiple fan circuit codes present

What to check

  • Read freeze frame and complete diagnostic data: fan requested status, engine temp, ignition state
  • Visually inspect fan relays, fuses, connectors and fan harness for damage/corrosion
  • Use a scan tool to command fan ON/OFF and compare requested vs actual status
  • Measure voltage at fan connector pins with fans commanded OFF and ON
  • Check ground continuity and resistance of fan motor and control circuit
  • Inspect for aftermarket devices or recent repairs that could backfeed the circuit

Signal parameters

  • Fan command from PCM/BCM (on/off/Duty cycle or PWM percentage)
  • Voltage at fan power pin (V) when command is OFF and when ON
  • Ground continuity (ohms) at fan motor ground
  • Fan tach/tellback signal frequency (Hz) or reported RPM when OFF
  • Current draw of fan motor (amps) when energized
  • PWM frequency and duty cycle on the control line (if applicable)

Diagnostic algorithm

  1. Retrieve all codes and freeze frame. Note whether PCM reports fan requested OFF but tach or voltage indicates fan activity.
  2. Visual inspection: check fuses, relays, connectors and wiring for heat damage, corrosion, or aftermarket splices.
  3. With a scan tool, command secondary fan ON then OFF while monitoring the fan status and tach signal. Confirm whether the module follows the command.
  4. With fan commanded OFF, probe the fan power lead for battery voltage. If B+ is present, suspect a stuck relay, short to B+, or backfeed. If no B+ but tach shows RPM, suspect tach/sensor fault or module error.
  5. Identify and test the relay: remove and bench-test or swap with known good relay. Check relay socket for permanent feed or welding.
  6. Disconnect fan motor connector while engine is cool and key on (or as safe/procedure allows). If fan stops supplying tach/power to the circuit when disconnected, isolate fault to fan assembly or motor wiring.
  7. Measure fan motor resistance and perform a current draw test when powered. Excessive current or abnormal resistance suggests motor internal fault.
  8. Inspect control module outputs: measure PWM signal, voltage, and ground at module pins. If module output is stuck high with correct commands, suspect module failure.
  9. Check for unintended backfeed from accessories (audio amps, aftermarket fans, relays). Disconnect suspected accessories and retest.
  10. Repair identified wiring faults, replace defective relay, fan assembly, or control module as indicated. Reprogram or update module software if manufacturer bulletin applies.
  11. Clear codes and road/idle test to confirm the fault does not return and that fan behavior matches commanded states.

Likely causes

  • Stuck relay or relay contacts welded closed feeding fan power
  • Short to B+ on the fan power or command circuit
  • Faulty fan control module with an output transistor shorted on
  • Fan motor generating voltage when spun (rare) or sending a false tach pulse
  • Backfeed from aftermarket device or improper wiring

Fault status

⚠️ Status
Secondary cooling fan circuit reports high speed or high circuit voltage while fan(s) are commanded OFF. Possible stuck relay, short to power, or failed fan control output.
🟡 Repair difficulty: Medium
⏱️ Diagnostic time: 1.0-2.5 hours

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