2021 Audi Q8 MIL On with Cooling System DTCs

Symptoms

Owners of affected 2021 Audi Q8 vehicles may notice the "MIL on" warning light illuminated on their dashboard. In some cases, the cooling fan might run permanently. These symptoms indicate a potential issue with the vehicle's cooling system.

Fault Codes / DTCs

If your Audi Q8 MIL on DTCs are stored in the Engine Control Module (ECM), J623 (address word 0001), they are likely related to this issue. At least two of the following DTCs will typically be present:

Code	Description
P218100	Fault in cooling system
P017B00	Sensor for cylinder head temperature, implausible signal
P308100	Engine temperature too low
P01E400	Sender 3 for coolant temperature, implausible signal

Diagnosis / Trigger Conditions

Diagnosis involves checking the thermostat. If the coolant is still warm, the thermostat should be placed in cold water to see if it restores its original closed condition. A faulty thermostat will show a gap between its chamber and seal, indicating it needs replacement. Technicians are required to document this with photos attached to the repair order.

Important Warnings

Audi explicitly states that replacing the coolant temperature sender will not resolve this issue. Claims submitted for parts replacement of the coolant temperature sender will be subject to review and may not be covered under warranty. This TSB, 01 20 82 2058767/6, supersedes previous bulletin Group 01 number 20-65 dated June 8, 2020.

Repair Procedure Summary

The primary repair involves replacing the faulty thermostat. The process includes:

1. Removing the existing thermostat.
2. Inspecting the thermostat for proper closure. If a gap is present between the chamber and seal, the thermostat is deemed faulty.
3. Replacing the faulty thermostat.
4. After the replacement, the coolant circuit must be refilled with G12evo coolant.

Required Tools or Parts

Technicians will require specific parts and tools for this repair:

• Part Number 06M121115K: Thermostat (Quantity: 01)
• Part Number 06M121688: Seal ring (Quantity: 01)
• Coolant G 12E0501GDSP: Up to 2 units
• Tool Number T40425: Thrust Piece (needed for seal replacement only)

Fasteners, bolts, nuts, and screws as needed should be sourced according to the repair manual or ETKA/ELSA.

Warranty Information

This repair is covered under warranty for vehicles up to 48 months or 50,000 miles. For Audi Certified Pre-Owned (CPO) vehicles, coverage falls under G10, requiring owner verification. If your vehicle is outside of these warranty parameters, this Technical Service Bulletin is for informational purposes only, and repair costs may apply. The service number for this claim is 1958, with a damage code of 0017.

Owner Action

If your 2021 Audi Q8 is displaying the "MIL on" warning light or exhibiting symptoms like the cooling fan running continuously, and you suspect an Audi Q8 MIL on DTCs issue, it is recommended to schedule an appointment with an authorized Audi service center. Provide them with details of the symptoms and any diagnostic trouble codes you may have observed.

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Source: NHTSA ID: 10179047