2021 Audi Q7/Q8 MIL On with Cooling System DTCs

Symptoms of a Cooling System Fault

Owners of affected Audi vehicles may notice the Malfunction Indicator Lamp (MIL) illuminated on their dashboard. In some cases, the engine cooling fan may run continuously or permanently. These symptoms are typically accompanied by specific Diagnostic Trouble Codes (DTCs) stored in the Engine Control Module (ECM).

Diagnostic Trouble Codes (DTCs)

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

Code	Description	Module
P218100	fault in cooling system	ECM
P017B00	sensor for cylinder head temperature, implausible signal	ECM
P308100	engine temperature too low	ECM
P01E400	sender 3 for coolant temperature, implausible signal	ECM

Important Owner Information

Audi explicitly states that replacing the coolant temperature sender will not resolve this issue. Claims for parts replaced incorrectly will be subject to review. This means owners should ensure that the proper diagnostic and repair procedures, as outlined in TSB 19 22 29 2058767/8, are followed to address the 2021 Audi Q8 cooling system fault.

Repair Procedure Summary

The primary repair involves inspecting and potentially replacing the thermostat. Technicians are instructed to remove the thermostat and check if it closes completely. If the coolant is still warm, the thermostat should be placed in cold water to restore its original condition for proper evaluation. If a gap is visible between the chamber and the seal, the thermostat is considered faulty and requires replacement. After the repair, the coolant circuit must be refilled with G12evo coolant.

Technicians are also required to attach photos to the repair order clearly showing that the thermostat does not close neatly, providing visual evidence of the fault.

Required Parts and Tools

To address the 2021 Audi Q8 cooling system fault, the following parts and a special tool may be required:

Part Number	Part Description	Quantity
06M121115K	Thermostat	01
06M121688	Seal ring	01
G 12E050SO	Coolant	Up to 02
See ETKA	Fasteners, Bolts, Nuts, and Screws	As needed

Special Tools:

• T40425: Thrust Piece (needed for seal replacement only)

Warranty Information

This repair is covered under warranty for up to 48 months or 50,000 miles, whichever comes first. For Audi Certified Pre-Owned (CPO) vehicles, the claim type is G10, and owner verification is required. Labor operations for thermostat removal and reinstallation are 1958 1993 (for most models) or 1958 1995 (for RS5 models only). Diagnostic time is allocated as GFF 0150 0000, with a maximum of 50 TU.

Revision History

This Technical Service Bulletin, 19 22 29 2058767/8, is a revision of an earlier bulletin, Group 19 number 21-13, dated March 2, 2021. Previous revisions included updates to warranty labor operations, required parts and tools (specifically the coolant part number), and revisions to the title and header information.

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Source: NHTSA ID: 10208895