P2B32

Code

Generic P — Powertrain

Fan 2 Stuck On

Brand: Generic

Type: P — Powertrain

Views: UK: 20 EN: 38 RU: 18

AI status

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Page language: EN

Causes

Stuck or welded fan relay or mechanical relay contacts
Shorted low-side driver (ECU/BCM/power module) causing constant ground
Short to battery (high side) feeding fan continuously
Faulty fan motor (internal short or internal control module) forcing ON
Wiring harness short or damaged connector allowing backfeed
Incorrect signal from body control module / HVAC control / engine control due to software or sensor fault

Symptoms

Cooling fan #2 runs continuously regardless of engine temperature or key position
Battery drains while vehicle is parked or after shutdown
Unusual fan noise or vibration (if motor failing)
Fan may stop only when fuse removed or battery disconnected
Possible MIL/CEL if control module detects driver circuit fault

What to check

Scan for related codes and view live data: fan requested state vs actual state, coolant temperature, HVAC requests
Visually inspect fan wiring, connector, and relay/fuse locations for damage or corrosion
Turn vehicle off and remove fan relay/fuse to see if fan stops (isolates power side)
Backprobe fan connector with ignition on to measure voltage and signal at the control pin
Disconnect fan motor connector to confirm if fan is receiving power or being backfed
Measure fan motor resistance and bench-test motor by applying battery voltage (observe current draw)

Signal parameters

Fan off: control output typically 0 V (or PWM 0% duty) on the low-side control; no battery feed on high side
Fan on: supply voltage ~11–14 V at fan power pin (high side) and low-side near 0 V when switched
PWM-controlled fans: duty cycle 0–100%; typical PWM frequency often 100–1000 Hz (manufacturer-specific)
Motor current: typical running current varies by vehicle (commonly 5–30 A); stall current higher—observe fuse/relay ratings
Resistance: fan motor DC resistance typically a few ohms; very low or open indicates fault

Diagnostic algorithm

Read and record all DTCs and freeze-frame data. Note fan requested state vs actual state in live data.
With ignition ON (engine off), observe fan status in scanner while commanding fan OFF/ON if possible. Note whether ECU is commanding OFF but fan remains ON.
Visually inspect fuses, relays, wiring harnesses and connectors for fan #2. Check for corrosion, melted insulation or obvious short paths.
Remove/withdraw the fan #2 relay or remove the fuse while fan is running. If fan stops, the high-side supply is being controlled by that relay/circuit — suspect relay or control circuit. If fan continues, suspect alternate feed or welded relay contacts.
Backprobe the fan connector: with fan expected OFF, check for battery voltage on the power pin and check control pin for unexpected ground. If power present when it should be off, trace high-side circuit. If control pin is grounded when it should be off, suspect low-side driver short.
Disconnect the fan motor connector. If fan stops when disconnected, the cause is upstream (relay, wiring, control module). If fan still runs after disconnection, check for mechanical/environmental reasons or incorrect observation (re-verify).
Bench-test fan motor by applying battery voltage directly (observe current and behavior). Excessive current, noise or binding indicates motor replacement.
If the control module low-side driver is suspected (driver shorted to ground), verify by checking continuity to ground with the relay removed and consult manufacturer wiring diagrams. Replace relay/module or repair wiring as indicated.
After repairs, clear codes and re-test under the same conditions to confirm the fault does not return.