2021 Audi e-tron Slow Charging DTC P31C500

Symptoms

Owners of affected 2021 Audi e-tron vehicles may experience the following issues related to battery charging:

• "The battery charging is very slow."
• After charging for 30 minutes or more, "the estimated charging time display changes from a normal time to an excessively long time (for example 36 hours or more when connected to a level 2 charger or DC fast charger)."

Fault Codes / DTCs

When diagnosing this slow charging condition, technicians may find the following Diagnostic Trouble Code (DTC) stored:

Diagnosis / Trigger Conditions

This issue originates from an incorrect calibration of the cooling system control valve during vehicle production. This calibration error can lead to excessive temperatures within the cooling system, which in turn negatively impacts the high-voltage battery's charging speed. Technicians should confirm the customer's reported symptoms and verify the presence of the Audi e-tron P31C500 DTC.

Repair Procedure Summary

The repair process for the 2021 Audi e-tron P31C500 slow charging issue involves diagnosing and potentially replacing specific coolant valves. The steps are as follows:

1. Check Vehicle History: Technicians must first review the vehicle's service history for any previously stored DTCs related to coolant valves in the thermal management control module, J1024 (address word 00C5).
2. Output Diagnosis (if DTC history exists): If relevant DTCs are found, an output diagnosis test should be performed for the specific coolant valve. If the values do not change during this test, the corresponding valve needs to be replaced according to the Elsa Repair Manual, which includes bleeding the cooling system.
3. Output Diagnosis (if no DTC history): If no prior DTCs for coolant valves in J1024 are found, the output diagnosis test should be performed starting with coolant valve 2 (N633), then coolant valve 4 (N635), and finally coolant valve 3 (N634) if necessary. If any of these valves show no change in values during the test, they must be replaced following the Elsa Repair Manual instructions, including the cooling system bleeding procedure.
4. Verification: After the repair is completed, the high-voltage battery must be rechecked to ensure it charges at a normal rate and that DTC P31C500 is no longer present.

Required Tools or Parts

Technicians will need the following parts if replacement is necessary:

• Coolant, fasteners, bolts, nuts, and screws as specified in ETKA/ELSA.
• 4KE963375J: Coolant valve 2 (N633)
• 4KE963375N: Coolant valve 4 (N635)
• 4KE963375H: Coolant valve 3 (N634)

Important Warnings

• Do not replace unnecessary parts: The Technical Service Bulletin explicitly states, "Only replace the actual valve that is defective." This guidance is critical to prevent unnecessary part replacements and associated costs.
• Warranty Coverage: This Technical Service Bulletin is informational only if the vehicle is outside of its warranty period. Warranty claims are covered for up to 48 months or 50,000 miles, and for CPO (Certified Pre-Owned) vehicles under G10 coverage. The Service Number for this bulletin is 1985 and the Damage Code is 0040.

Source: NHTSA ID 10201539