2023-2025 Audi Air Suspension Fault C118D01 TSB

Owners of various 2023-2025 Audi models may encounter an 'Air suspension: system fault' message displayed in the instrument cluster. This condition is often linked to a specific Diagnostic Trouble Code (DTC) C118D01, indicating an electrical error within the air suspension's level control compressor system. Audi Technical Service Bulletin (TSB) 2073034/5, issued on May 14, 2024, provides detailed guidance for diagnosing and resolving this issue.

This TSB supersedes an earlier version, Group 43 number 24-88, dated May 7, 2024, reflecting updated warranty information and added model years. The primary focus of the bulletin is to address malfunctions related to the compressor electronics J1135, which can lead to the Audi e-tron C118D01 fault.

Symptoms

The most common symptom reported by owners is the appearance of the warning message:

• "Air suspension: system fault"

This message is displayed prominently in the vehicle's instrument cluster, alerting the driver to a potential issue with the air suspension system.

Fault Codes / DTCs

When diagnosing the 'Air suspension: system fault' message, technicians will typically find the following Diagnostic Trouble Code (DTC) logged in the suspension control unit -J775- (diagnostic address 0074):

Code	Description	Module
C118D01	Compressor for level control electrical error	J775 (Suspension Control Unit)

Diagnosis / Trigger Conditions

Diagnosis for the Audi e-tron C118D01 fault begins by verifying the part number of the compressor electronics. The described repair procedure specifically applies if the compressor electronics have part number index A (affected part number 4M0.907.778.A).

Technicians should first inspect the wiring and contacts at both the air compressor and the compressor electronics control unit J1135 for any irregularities. If no issues are found with the wiring or contacts, further steps are required based on the DTC's status.

Important Warnings

Audi emphasizes specific instructions to ensure the correct repair and prevent unnecessary part replacement:

• If the DTC C118D01 is logged as active/static and remains active/static after cycling the ignition, the control unit for compressor electronics J1135 must be replaced. It is crucial to not replace the air compressor itself; only the compressor electronics control unit J1135 should be replaced.
• When replacing the control unit, technicians must use part number 4M0.907.778 (Without index A).
• The part numbers listed in this TSB may differ from those found in ETKA. It is mandatory to only use the part numbers specified in this TSB, which includes any superseding part numbers.

Repair Procedure Summary

The repair process for the Audi e-tron C118D01 issue involves several key steps:

1. Initial Verification: Confirm that the vehicle's compressor electronics are part number 4M0.907.778.A. This is a critical first step to ensure the TSB applies.
2. Wiring and Contact Inspection: A thorough check of the wiring and electrical contacts at both the air compressor and the compressor electronics control unit J1135 is performed to rule out simple connection issues.
3. DTC Handling (Passive/Intermittent): If the DTC C118D01 is found to be passive or intermittent, the technician will attempt to delete the DTC from the system.
4. DTC Handling (Active/Static): If the DTC C118D01 is active/static and persists even after turning the ignition off and then on again, the control unit for compressor electronics J1135 must be replaced. The TSB explicitly states to replace only the control unit J1135, not the entire air compressor.
5. Re-evaluation for Persistent Intermittent DTC: If DTC C118D01 is stored a second time as passive/intermittent in the J775 control unit, the J1135 unit should also be replaced.

Audi plans to release improved software for the compressor electronics J1135 to address this issue in future production.

Required Tools or Parts

For the repair, the following parts are specified:

• Fasteners, Bolts, Nuts, and Screws: As needed, per the Repair Manual (See ETKA/ELSA for specific quantities).
• Control unit for compressor electronics J1135: Part Number 4M0.907.778 (Quantity: 01). This part number is to be used without an index A.

Warranty Information

Warranty claims related to TSB 2073034/5 are covered under specific conditions:

• Claim Type 110: Applicable for vehicles up to 48 months or 50,000 miles.
• Claim Type G10: For Certified Pre-Owned (CPO) vehicles, after verifying ownership.
• If the vehicle is outside of any warranty coverage, this Technical Service Bulletin serves as informational guidance only.

Service Number: 4316 Damage Code: 0039

Labor Operations:

• Remove and install control unit J1135 (Labor operation code: 4316 19xx)
• Charge battery (Labor operation code: 2706 8950)
• Diagnostic Time: GFF (Labor operation code: 0150 0060), maximum 50 time units.
• Road test prior to and after service procedure: No allowance (0 TU).

All warranty claims must adhere to the Audi Warranty Policies and Procedures Manual.

Source: NHTSA ID: 11002126