2023-2025 Audi Q8 Fuel Delivery Error TSB 2079461/2

Audi has released Technical Service Bulletin (TSB) 2079461/2 to address a specific fuel system concern affecting various 2020-2025 models, including the 2023-2025 Audi Q8. This bulletin provides diagnostic and repair procedures for vehicles experiencing an illuminated Malfunction Indicator Lamp (MIL) or activating the limp-home function due to Diagnostic Trouble Codes (DTCs) P014800 or P008700 being stored in the Engine Control Unit (ECM).

This issue, often referred to as an Audi Q8 fuel delivery error P014800 or a fuel rail/system pressure problem, points to potential malfunctions within the vehicle's fuel supply system, specifically involving the high-pressure fuel pump. The TSB outlines steps for technicians to accurately diagnose and resolve these fuel system errors.

Symptoms You Might Experience

Owners of affected Audi vehicles may notice one or both of the following symptoms:

• The Malfunction Indicator Lamp (MIL), commonly known as the "Check Engine" light, illuminates on the dashboard.
• The vehicle enters "limp-home function" mode, which typically restricts engine power and speed to prevent further damage, allowing the driver to reach a service center safely.

These symptoms are direct indicators that the Engine Control Unit (ECM) has detected a fault within the fuel system.

Fault Codes (DTCs) and Their Meanings

When the MIL light is on or the limp-home function activates, the ECM, specifically the Engine Control Unit -J623- (address word 0001), will log specific Diagnostic Trouble Codes. These codes pinpoint the nature of the fuel system problem:

Code	Description	Module	Symptom	Status
P014800	Fuel Delivery Error	Engine Control Unit -J623-	N/A	N/A
P008700	Fuel Rail/System Pressure - Too Low	Engine Control Unit -J623-	15059	11101101

These codes indicate that the fuel delivery system is not operating within its specified parameters, leading to insufficient fuel pressure or an overall fuel delivery issue.

Diagnosis and Trigger Conditions

Diagnosis for the Audi Q8 fuel delivery error P014800 or P008700 begins with clearing the stored DTCs from the Engine Control Unit. If the DTCs reappear after clearing, technicians are instructed to perform specific tests related to the low-pressure fuel pump, as outlined in the ELSA repair manual. This initial step helps determine if the fault is persistent or intermittent.

Key diagnostic tests include:

• "Checking fuel delivery rate": This test assesses the volume of fuel being supplied by the low-pressure pump.
• "Pressure test in the fuel supply line": This measures the actual fuel pressure within the low-pressure side of the fuel system.

For concerns that are reproducible or static, a more detailed procedure is followed:

1. A VAS 6550 pressure gauge is installed on the low-pressure side, just before the high-pressure fuel pump. This allows for real-time monitoring of the in-line fuel pressure. Simultaneously, the ODIS-S self-diagnosis function is used to graph measured high-pressure values (Actual vs. Specified).
2. While the engine is running, both the low-side and high-side fuel pressures are monitored. If the low-side pressure does not drop below 3 bar and the high-side pressure does not exceed 20 bar, the high-pressure fuel pump is identified as the likely culprit and should be replaced.

For repeat repairs where the concern is not consistently reproducible, technicians are advised to check the expanded ambient conditions associated with DTCs P014800 and P008700. If the fuel rail pressure on the high-pressure side is approximately 10 bar, the high-pressure fuel pump should be replaced before considering other components of the fuel system. An example provided in the TSB shows an actual fuel pressure of 880 kPa (8.8 bar) against a specified value of 243.5 bar, clearly indicating the need for high-pressure fuel pump replacement.

Repair Procedure Summary

The primary repair for the P014800 or P008700 fault involves the diagnosis and potential replacement of the high-pressure fuel pump. The general procedure is as follows:

1. Initial Check: Clear the DTCs from the Engine Control Unit. If the fault codes return, proceed with further diagnostics.
2. Low-Pressure System Tests: Conduct specific tests on the low-pressure pump, including checking the fuel delivery rate and performing a pressure test in the fuel supply line, as guided by the ELSA repair manual.
3. Pressure Monitoring: For persistent issues, connect a VAS 6550 pressure gauge and use ODIS-S diagnostic software to monitor both low-side and high-side fuel pressures while the engine is running.
4. High-Pressure Fuel Pump Replacement: If the low-side pressure remains above 3 bar and the high-side pressure does not go above 20 bar, the high-pressure fuel pump is deemed faulty and must be replaced. This is the most common resolution for the Audi Q8 fuel delivery error P014800.
5. Repeat Repair Scenario: In cases of intermittent or repeat issues where the fault is not easily reproducible, if the high-pressure fuel rail pressure is found to be around 10 bar, the high-pressure fuel pump should be replaced as the first step, prior to investigating other fuel system components.

Required Tools or Parts

To perform the diagnosis and repair outlined in TSB 2079461/2, technicians will require specific tools and potentially new parts:

• VAS 6550 pressure gauge: Essential for accurately measuring fuel pressure.
• ODIS-S diagnostic software: Used for reading DTCs, monitoring live data, and performing guided functions.
• High-pressure fuel pump: The primary replacement part if diagnostics confirm its failure.

Warranty Information

This Technical Service Bulletin provides detailed warranty claim information. The Service Number associated with this repair is 2363, and the Damage Code is 0010. Labor operations are specified with unique codes for various tasks:

• Remove and install high-pressure pump: 2463 19XX
• Remove and install 2 high-pressure pumps: 2463 20XX
• Check fuel pump: 2066 0199 (50 TU)
• Remove and install cover: 1083 1900
• Remove and install air filter housing (gasoline engines): 2425 19XX
• GFF/ Guided Functions: 0150 0060

All warranty claims must adhere to the Audi Warranty Policies and Procedures Manual. The claim comment should state "As per TSB 2079461/2".

Important Warnings for Owners

Owners should be aware that if their vehicle is outside of its warranty period, this Technical Service Bulletin is for informational purposes only. The repair costs may not be covered by Audi in such cases. It is always recommended to consult with an authorized Audi service center to discuss specific warranty coverage and repair options.

Source: NHTSA ID 11026228