2021-2025 Audi A4/A5 Engine Coolant Temperature Sensor TSB

Owners of certain 2021-2025 Audi A4, A4 allroad, and A5 models (types 8W* and F5* with DPAA engine code) may encounter an issue where the exhaust emissions warning lamp (MIL) illuminates on the instrument cluster. This often indicates a problem within the engine's cooling system, specifically related to a sensor reading. This Technical Service Bulletin (TSB) 2078939/1, released on August 15, 2025, provides guidance for diagnosing and resolving this condition, which is often linked to the Audi A5 DTC P218500.

Symptoms

The primary symptom reported by customers is the illumination of the "exhaust emissions warning lamp (MIL) lights up in the instrument cluster." This warning light can be accompanied by an "emissions control system malfunction display" message, indicating an issue with the vehicle's emissions control system. Furthermore, owners might observe a general malfunction display related to "information, navigation, communication, entertainment -> malfunction display symbols -> emissions control system malfunction display," or a specific concern regarding "engine -> cooling system -> coolant temperature sensor functionality -> no function."

Fault Codes / DTCs

When the exhaust emissions warning lamp is active, a scan of the vehicle's engine control module (-J623-) will typically reveal the following Diagnostic Trouble Code (DTC):

This DTC, P218500, points directly to a high circuit reading from the Engine Coolant Temperature Sensor 2, which is identified as temperature sender G83. The code can be stored intermittently or statically, indicating a persistent issue.

Diagnosis

Upon encountering the "exhaust emissions warning lamp (MIL) lights up in the instrument cluster" symptom or the Audi A5 DTC P218500, technicians will perform a Guided Fault Finding (GFF) procedure. This diagnostic process is designed to pinpoint the exact cause of the P218500 code. The TSB indicates that a fault affecting the temperature sender G83 is typically identified during this diagnostic step, confirming the sensor as the root cause of the cooling system malfunction.

Repair Procedure Summary

The recommended repair for the Audi A5 DTC P218500 involves replacing the faulty temperature sender G83. During the replacement process, it is crucial to ensure that the connecting cable for the new temperature sender is installed without any tension. This careful attention to detail helps prevent future issues and ensures proper sensor function and longevity. The labor operation for this procedure is documented as "Remove and install temperature sender G83."

Warranty Information

This Technical Service Bulletin (TSB 2078939/1) outlines specific warranty claim details for the repair:

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