2025-2026 Audi A5, Q5 P01C400 Fuel Rail Sensor TSB

Audi has issued Technical Service Bulletin (TSB) 2080446/1 to address an issue affecting certain 2025-2026 Audi A5 and Q5 vehicles. Owners may notice an illuminated exhaust emissions warning lamp in their instrument cluster, often accompanied by a specific diagnostic trouble code. This TSB provides a solution for this concern, which stems from a software issue within the engine control unit.

This bulletin, identified as 2080446/1, outlines the steps for authorized Audi service centers to resolve the problem by performing a software update. The primary concern is related to the fuel rail pressure sensor's performance, leading to the warning light.

Symptoms

Owners of affected 2025-2026 Audi A5 or Q5 vehicles may observe the following symptom:

• The exhaust emissions warning lamp lights up in the instrument cluster.

Fault Codes / DTCs

When diagnosing this issue, technicians may find the following diagnostic trouble codes (DTCs) logged in the engine control module, identified as -J623- (address word 0001):

Code	Description	Symptom Code(s)
P01C400	"Fuel Rail Pressure Sensor 1 Range/Performance"	46314, 46312

Diagnosis / Trigger Conditions

The root cause of the "Fuel Rail Pressure Sensor 1 Range/Performance" fault, indicated by DTC P01C400, has been identified as a software issue within the engine control unit. This software anomaly can lead to incorrect readings or interpretations, triggering the exhaust emissions warning lamp.

Important Warnings for Owners

Audi has provided specific advisories for owners regarding this software update:

• "Please inform the customer that this software update may neutralize previous modifications to the vehicle software performed by either the customer or other third parties."
• "If the customer declines the software update, please inform them that this could lead to issues or restrictions with the use of the vehicle or individual components."

Owners who have had their vehicle's software modified (e.g., tuning or retrofitting) should be aware that this update may revert those changes. Declining the update could result in continued issues or limitations with vehicle functions.

Repair Procedure Summary

The prescribed repair for the 2025-2026 Audi A5 or Q5 experiencing the Audi A5 P01C400 issue is a software update for the engine control unit. This update is detailed in TSB 2079690, titled "Combined software update 03.10.00/C (28.13.01) KD2." Technicians are instructed to check for the visibility of TSB 2079690 for the specific vehicle and perform the update as described.

The software update process involves connecting a battery charger to maintain stable voltage. It also includes preliminary and follow-up work such as a bus sleep cycle and a calibration drive to ensure proper integration and functionality of the new software. If the flashing process is interrupted, additional steps are required to restart the software update.

Warranty Information

For vehicles still under warranty, this software update is typically covered. The claim type is informational only if the vehicle is outside of warranty. The following codes are relevant for warranty claims:

| Field | Code / Description ```callout Q: What causes the exhaust emissions warning lamp to light up in my Audi A5 or Q5 (2025-2026 model year) with DTC P01C400?

A: The exhaust emissions warning lamp, often accompanied by DTC P01C400 "Fuel Rail Pressure Sensor 1 Range/Performance" (symptom codes 46314, 46312), is caused by a software issue in the engine control unit, as identified in Audi Technical Service Bulletin 2080446/1.

Audi has released Technical Service Bulletin (TSB) 2080446/1 to address a specific concern affecting certain 2025-2026 Audi A5 and Q5 vehicles. This bulletin provides a solution for owners who experience an illuminated exhaust emissions warning lamp in their instrument cluster, which is often accompanied by the diagnostic trouble code (DTC) P01C400. The underlying cause has been identified as a software issue within the vehicle's engine control unit.

This TSB, identified as 2080446/1, outlines the necessary repair procedure for authorized Audi service centers. The primary focus is to resolve the "Fuel Rail Pressure Sensor 1 Range/Performance" fault through a targeted software update, ensuring the vehicle's emission systems function correctly.

### Symptoms

Owners of affected 2025-2026 Audi A5 or Q5 vehicles may observe a clear indication of this issue:

*   The exhaust emissions warning lamp lights up in the instrument cluster.

### Fault Codes / DTCs

When diagnosing this specific problem, technicians will typically find the following diagnostic trouble code (DTC) logged in the engine control module, which is identified as -J623- (address word 0001):

| Code    | Description                                     | Symptom Code(s) |
| :------ | :---------------------------------------------- | :-------------- |
| P01C400 | "Fuel Rail Pressure Sensor 1 Range/Performance" | 46314, 46312    |

These codes indicate that the engine control unit is detecting an anomaly in the performance or range of the fuel rail pressure sensor, triggering the emissions warning.

### Diagnosis / Trigger Conditions

The root cause for the DTC P01C400 and the illuminated exhaust emissions warning lamp has been pinpointed to a software issue within the engine control unit. This software anomaly can lead to incorrect monitoring or interpretation of the fuel rail pressure sensor's data, even if the sensor itself is functioning correctly. The issue is not a hardware failure but rather a calibration or logic error in the engine's control software.

### Important Warnings for Owners

Audi has included critical advisories for owners considering this software update. It is essential to be aware of these points before proceeding with the repair:

*   "Please inform the customer that this software update may neutralize previous modifications to the vehicle software performed by either the customer or other third parties."
*   "If the customer declines the software update, please inform them that this could lead to issues or restrictions with the use of the vehicle or individual components."

Owners who have previously had their vehicle's engine software modified for performance tuning, aftermarket accessories, or other reasons should understand that this official Audi update may overwrite or render those modifications ineffective. Furthermore, declining the recommended software update could result in the continuation of the exhaust emissions warning lamp issue and potentially lead to other unforeseen operational restrictions or problems with individual vehicle components.

### Repair Procedure Summary

The prescribed repair for the Audi A5 P01C400 issue in affected 2025-2026 Audi A5 and Q5 models is a software update for the engine control unit. This update is specifically detailed in Audi Technical Service Bulletin 2079690, which is titled "Combined software update 03.10.00/C (28.13.01) KD2." Technicians are instructed to verify if TSB 2079690 is applicable to the specific vehicle and then perform the software update as outlined in that bulletin.

The software update process is comprehensive and includes several steps to ensure successful implementation. This involves connecting a battery charger to the vehicle to maintain a stable power supply throughout the programming process, which is crucial for preventing interruptions. The procedure also incorporates preliminary and follow-up tasks, such as allowing for a bus sleep cycle and performing a calibration drive. These steps help ensure that the new software integrates correctly with all vehicle systems and that all parameters are properly adapted. In cases where the software flashing process is interrupted or aborted, specific additional steps are required to safely restart and complete the update.

### Warranty Information

For vehicles that are still covered under the manufacturer's warranty, the software update described in TSB 2080446/1 is typically performed at no charge. If the vehicle is outside of its warranty period, this Technical Service Bulletin serves as informational guidance for diagnosis and repair. The following details are relevant for warranty claims:

*   **Claim Type:** Informational only if the vehicle is outside of any warranty.
*   **Service Number:** 2470
*   **Damage Code:** KD02
*   **Labor Operations:** Software update, including connecting battery charger (Code: 0151 0010).
*   **Fixed Rate for Software Update:** This includes all required preliminary and follow-up work, such as the bus sleep cycle, calibration drive, and restarting the software update if flashing is aborted (Code: 0151 0040, 130 TU).

All warranty claims must adhere to the Audi Warranty Policies and Procedures Manual and are subject to review by Audi Warranty. When performing combined software updates, time stamps are not required for billing under warranty, allowing technicians to work on other vehicles concurrently. The combined software update can also be performed by non-productive personnel.

### Superseded Bulletins

This Technical Service Bulletin 2080446/1 replaces a previous bulletin, PSS 2080114, which also addressed an engine control module issue related to the fuel rail pressure sensor P01C400 (symptom 46314) for 4-cylinder 2.0 TFSI engines.

### Owner Action

If your 2025-2026 Audi A5 or Q5 is displaying the exhaust emissions warning lamp or you suspect an issue related to DTC P01C400, it is recommended to schedule an appointment with an authorized Audi dealer. The dealer will be able to diagnose the vehicle and perform the necessary software update as outlined in TSB 2080446/1. Be prepared to discuss any prior software modifications to your vehicle with the service advisor.

NHTSA ID: 11027384