P1671 Engine compartment purge fan output stage

P1671 Engine compartment purge fan output stage

The code P1671 "Engine compartment purge fan output stage" is specific to Porsche vehicles, 

indicating a fault within the fan system that cools the engine bay. The "output stage" is the component that controls the fan's speed. 

What the engine compartment purge fan does

This fan manages the heat load in the engine bay and is particularly active on hot days or after the car has been driven hard. It can continue to run for some time after the engine has been turned off to help dissipate heat. 

Possible causes of P1671

A diagnostic scan may reveal more specific details, such as the exact nature of the electrical fault (e.g., short circuit to ground, short to positive, or open circuit). 

• Defective output stage or fan: The fan itself or its output stage may have failed and must be replaced.
• Wiring issue: There may be an open circuit or a short in the wiring to the fan's output stage.
• Blown fuse or bad relay: A failed fuse or relay can interrupt power to the fan. This is one of the first things to check.
• Faulty engine compartment temperature sensor: If the temperature sensor has fallen out of its holder and is resting on a hot engine component, it can send a false signal to the control unit, causing the fan to run excessively or trigger a fault code.
• Control module fault: Less commonly, a faulty engine control module (ECM) could be the root cause. 

How to diagnose and fix the problem

1. Perform a system scan: Use a scan tool to confirm the code and check for any other related fault codes. A tool like a Durametric can be used to manually activate the fan to verify if it is working.
2. Check the fan: A simple test is to run the engine to operating temperature and then turn on the A/C to maximum. This should trigger the fan. If it doesn't, inspect the fan for proper operation.
3. Inspect fuses and relays: Check the fuse panel and relay locations for any blown fuses or faulty relays related to the engine compartment cooling fans.
4. Inspect the temperature sensor: Visually inspect the engine compartment temperature sensor to ensure it is securely in place. If it has come loose and is touching hot components, reseat it correctly.
5. Examine the wiring: Look for any signs of damage to the wiring harness connected to the fan and its control unit, including melted or exposed insulation.
6. Replace components: If testing indicates a specific component is faulty, replace it. The purge fan is typically replaced as a complete unit.