2021 Audi Q7, Q8 MIL On with Cooling System DTCs

Symptoms

Owners of 2021 Audi Q7 and Q8 vehicles may notice the Malfunction Indicator Lamp (MIL) illuminated on the dashboard. Another symptom of a potential 2021 Audi Q8 cooling system fault is the engine cooling fan running permanently.

Fault Codes / DTCs

When diagnosing a 2021 Audi Q8 cooling system fault, technicians may find at least two of the following Diagnostic Trouble Codes (DTCs) stored in the Engine Control Module (ECM), specifically J623 (address word 0001):

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

Important Warnings

Audi advises against replacing the coolant temperature sender as a solution for this issue. The manufacturer states, "Parts replacement of the coolant temperature sender does not solve this issue. Claims for replaced parts will be subject to review." This warning highlights that the root cause of the 2021 Audi Q8 cooling system fault is not the sender itself.

Diagnosis / Trigger Conditions

The primary diagnostic step for this 2021 Audi Q8 cooling system fault involves inspecting the thermostat. The thermostat should be removed and checked to ensure it closes completely. If the coolant is still warm, the thermostat can be placed in cold water to help it return to its original closed condition for proper evaluation. If a visible gap exists between the chamber and the seal, the thermostat is considered faulty and requires replacement.

Repair Procedure Summary

The repair for this condition, as outlined in Technical Service Bulletin 2058767/7, focuses on replacing the faulty thermostat. The general procedure involves:

1. Removing the existing thermostat from the vehicle.
2. Inspecting the thermostat for proper closure. If it does not close completely, it is deemed faulty.
3. Replacing the faulty thermostat with a new one.
4. After the replacement, the cooling system must be refilled with G12evo coolant.
5. Technicians are required to attach photos to the repair order clearly showing the thermostat did not close properly.

Required Parts and Tools

To address the 2021 Audi Q8 cooling system fault, specific parts and a special tool are required:

• Thermostat: Part number 06M121115K (Quantity: 01)
• Seal ring: Part number 06M121688 (Quantity: 01)
• Coolant: Part number G 12E050S0 (Quantity: Up to 02)
• Fasteners, Bolts, Nuts, and Screws: As needed per the repair manual (See ETKA/ELSA)
• Thrust Piece: Tool number T40425 (Needed for seal replacement only)

Warranty Information

This repair is covered under warranty for eligible vehicles. For vehicles within 48 months or 50,000 miles, Claim Type 110 applies. For Audi Certified Pre-Owned (CPO) vehicles, Claim Type G10 is used, requiring owner verification. If the vehicle is outside of warranty, this Technical Service Bulletin is for informational purposes only.

The Service Number for this operation is 1958, with a Damage Code of 0017. Labor operations for thermostat removal and reinstallation are 1958 1993, or 1958 1995 for RS5 models only. Additional labor operations may be required for intake air distributor, cooling fan housing, or front bumper removal, depending on the specific vehicle and engine configuration. Diagnostic time is GFF 0150 0000, with a maximum of 50 Technical Units (TU). Road tests before and after the service procedure have no allowance (0 TU). All warranty claims must comply with the Audi Warranty Policies and Procedures Manual. This Technical Service Bulletin 2058767/7 supersedes Technical Service Bulletin Group 01 number 20-82 dated August 26, 2020.

Source: NHTSA ID 10188591