P0485 Mercedes-Benz Code - Cooling Fan Power/Ground Circuit Malfunction
Quick Answer
The electric cooling fan is controlled by the Engine Control Module (ECM) through the cooling fan relay based on inputs from the following components: - The engine coolant temperature (ECT) sensor - The intake air temperature (IAT) sensor - The A/C selector switch - The A/C refrigerant pressure sensor - The vehicle speed sensor (VSS) The ECM controls the cooling fan by grounding the cooling fan control circuit which turns ON the cooling fan relay. Common causes include Faulty fan control relay, Faulty cooling fan, Fan control relay harness is open or shorted. Severity is High - diagnose this code as soon as possible. Driving is not recommended if the warning light is flashing, the engine runs poorly, or safety-related symptoms are present.
- What it means
- P0485 Mercedes-Benz indicates Cooling Fan Power/Ground Circuit Malfunction.
- Common causes
- Common causes include Faulty fan control relay, Faulty cooling fan, Fan control relay harness is open or shorted.
- Severity
- High - diagnose this code as soon as possible.
- Can I drive?
- Driving is not recommended if the warning light is flashing, the engine runs poorly, or safety-related symptoms are present.
Code P0485 Mercedes-Benz Description
- The engine coolant temperature (ECT) sensor
- The intake air temperature (IAT) sensor
- The A/C selector switch
- The A/C refrigerant pressure sensor
- The vehicle speed sensor (VSS)
The ECM controls the cooling fan by grounding the cooling fan control circuit which turns ON the cooling fan relay. The cooling fan relay will be commanded ON when the following conditions are met:
- The engine coolant temperature reaches 106°C (223°F) or more.
- The A/C clutch requested.
- The vehicle speed is less than 38 MPH.
The cooling fan relay will be commanded ON regardless of vehicle speed when the following conditions are met:
- The engine coolant temperature is 151°C (304°F) or more.
- The A/C refrigerant pressure is high.
The cooling fan may be commanded ON when the engine is not running under a fan run-on conditions described in the electric cooling fan general description portion of the service manual.
What are the Possible Causes of the DTC P0485 Mercedes-Benz?
- Faulty fan control relay
- Faulty cooling fan
- Fan control relay harness is open or shorted
- Fan control relay circuit poor electrical connection
- Fan cooling fan harness is open or shorted
- Fan cooling fan circuit poor electrical connection
How to Fix the DTC P0485 Mercedes-Benz?
Review the 'Possible Causes' above and visually examine the corresponding wiring harness and connectors. Check for damaged components and inspect connector pins for signs of being broken, bent, pushed out, or corroded.
What is the Cost to Diagnose the Code?
Labor: 1.0
To diagnose the P0485 Mercedes-Benz code, it typically requires 1.0 hour of labor. Rates vary by location, vehicle, and shop. Many shops charge between $80–$150 per hour; dealerships and metro areas may be higher, independents may be lower.
Need more information about the P0485 Mercedes-Benz code?
Need more information on how to fix the P0485 Mercedes-Benz code? Get Access to Factory Service Manuals
Need Help with the Code?
Get the P0485 Mercedes-Benz code diagnosed by a professional: Find a repair shop in your area
Frequently Asked Questions about P0485 Mercedes-Benz Code
1. What does the OBDII code P0485 mean on a Mercedes-Benz?
P0485 indicates a Cooling Fan Power/Ground Circuit Malfunction, meaning there’s an issue with the electrical circuit that powers or grounds the cooling fan.
2. What are the common symptoms of a P0485 code on a Mercedes-Benz?
Symptoms include engine overheating, the cooling fan not working, an illuminated check engine light, and potential reduced air conditioning performance.
3. What causes the P0485 code on a Mercedes-Benz?
Common causes include a faulty cooling fan motor, damaged wiring or connectors in the fan circuit, a blown fuse, or a malfunctioning cooling fan relay.
4. Can I drive my Mercedes-Benz with a P0485 code?
Driving with a P0485 code can lead to engine overheating, which can cause severe engine damage. It is recommended to address the issue promptly.
5. How do I diagnose the P0485 code on my Mercedes-Benz?
Start by inspecting the cooling fan, wiring, and connectors for damage or corrosion. Check the fuse and relay, and use a multimeter to test for proper voltage and ground in the circuit.
6. How is the P0485 code fixed on a Mercedes-Benz?
Repairs may include replacing a faulty cooling fan motor, repairing damaged wiring, replacing a blown fuse, or installing a new cooling fan relay.
7. How much does it cost to fix the P0485 code on a Mercedes-Benz?
The repair cost depends on the issue. Replacing a cooling fan motor can cost $300–$700, while wiring or relay repairs may be less expensive.
8. Can a bad cooling fan relay trigger the P0485 code?
Yes, a faulty cooling fan relay can disrupt power or ground to the fan, triggering the P0485 code.
9. Will clearing the P0485 code fix the problem?
Clearing the code will remove the check engine light temporarily, but the issue will persist if the underlying cause is not repaired.
10. Can low coolant levels cause the P0485 code on a Mercedes-Benz?
Low coolant levels do not directly cause the P0485 code, but they can contribute to engine overheating, which may indirectly affect the cooling fan system.
Discuss the causes and fixes for P0485 Mercedes-Benz OBDII Code
Code P0485 Mercedes-Benz comments
No comments found for this page.
Fix Your Car Smarter
Try the New AutoCodes App!
Get complete OBDII diagnostics, repair solutions, and cost estimates, plus AI chat support on demand.
