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DTC codes / P2Bxx · Hybrid propulsion / P2B30

P2B30Fan 1 Stuck On

P2B30 indicates that the powertrain control module (PCM) has commanded the engine cooling fan relay to turn off, but the fan circuit remains energized and the fan continues to run. The PCM detects this by monitoring the fan control circuit and seeing voltage or current that indicates the fan is still active when it should be off, which can lead to battery drain and cooling system issues.

SystemPowertrain
Code typeGeneric (all makes)
SeverityMedium
Fix difficultyIntermediate
AreaHybrid propulsion

Symptoms you may notice

  • The engine cooling fan runs continuously even after the engine is shut off and cooled down.
  • The battery may drain overnight, causing a no-start condition.
  • The fan may run at full speed immediately after starting the engine, even when cold.
  • Often no symptoms besides the warning light if the fan only sticks occasionally.
  • Possible overheating if the fan control module is damaged and fails to activate the fan when needed.
  • A humming or whirring noise from the engine bay when the ignition is off.

Common causes, most likely first

  1. A stuck closed cooling fan relay, keeping power applied to the fan motor.
  2. A short to power in the fan control wiring between the relay and the fan motor.
  3. A faulty fan control module that internally shorts and keeps the fan energized.
  4. A failed PCM driver that remains grounded, keeping the relay coil energized.
  5. Corroded or damaged connectors in the fan circuit causing unintended continuity.
  6. An aftermarket or incorrectly installed fan override switch or wiring.

How to diagnose and fix it

  1. Verify the fan operation by observing it with the engine off and key removed; if it runs, proceed to check the relay.
  2. Locate the cooling fan relay and test it for continuity across the switch terminals; replace if stuck closed.
  3. Disconnect the fan motor connector and check for power on the control circuit with the key off; if power is present, trace the short.
  4. Inspect the wiring harness for chafed or melted wires near the fan and relay, repairing as needed.
  5. Test the fan control module if equipped, by backprobing the control signal and checking for correct voltage changes.
  6. Check the PCM driver by commanding the fan on and off with a scan tool and monitoring the control circuit; replace PCM if the driver is faulty.
  7. Clear the code and perform a road test to confirm the fan cycles correctly and the code does not return.

Why the fan runs with the key off

  • A stuck fan relay is the most common cause, but many technicians overlook that the relay can be triggered by a faulty coolant temperature sensor reading that keeps the PCM commanding the fan on.
  • The code can set intermittently if the fan only sticks occasionally, so a relay that tests good when cold may still be the culprit after warming up.
  • Some vehicles use a pulse-width modulated fan controller; a shorted control wire can cause the fan to run at full speed, mimicking a stuck relay.
  • A failing battery or charging system can cause voltage spikes that confuse the PCM and set this code without any actual fan fault.
  • After replacing a fan motor or relay, always clear adaptive learning and verify the fan turns off within the specified time after the engine is shut off.

Can I keep driving with P2B30?

You can drive the vehicle short distances to a repair shop, but avoid leaving it parked for long periods because the fan may drain the battery. Do not ignore the warning light, as a continuously running fan can overheat the fan motor and cause a fire risk in rare cases.

Tools that help

Tools we recommend are in the Auto Veteran shop on Amazon. As an Amazon Associate we earn from qualifying purchases.

Guidance is general and written for all OBD-II vehicles. Exact tests and values vary by model, so confirm the fault before replacing parts.

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