When an Audi arrives with no keys or a faulty ignition system, getting it to power up for diagnostics can be a challenge. This article addresses how to use VCDS (Vag-Com Diagnostic System) to troubleshoot an Audi when “no keys installed” is the problem, focusing on waking up the CAN bus and accessing critical control modules.
Waking Up the CAN Bus without Keys
Often, the vehicle’s systems need to be “woken up” to establish communication with VCDS. Since there are no keys, the standard ignition-on method won’t work. Here’s a proven technique:
- Foot on Brake: Depress and hold the brake pedal.
- Hazards On: Turn on the hazard lights.
- Flash High Beams: Pull and hold the high beam “flash to pass” lever.
- Wait and Connect: Maintain these positions for 5-10 seconds, allowing the CAN bus to activate. Then, attempt to connect VCDS to the [05 – Acc/Start Auth.] controller.
This method often enables communication with multiple controllers, allowing you to read and clear fault codes.
Key Components in Audi Starting System
Understanding the key components involved in the starting process is crucial for effective troubleshooting:
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J518 – Access/Start Control Module: This module is the brain of the operation, responsible for authorizing the vehicle start. It needs to receive a valid key signal and confirmation from the steering lock actuator.
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E415 – Access/Start Authorization Switch: This is the component in the ignition switch where the key is inserted and read. In a “no keys” scenario, this component won’t provide the necessary signal.
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N360 – Steering Column Lock Actuator: This actuator is responsible for locking and unlocking the steering column. Its proper function is crucial for the J518 to authorize engine start. In Audis, the N360 is integrated into the steering column assembly (part # 4E0419512GX) and requires the immobilizer PIN code for replacement and adaptation.
If any of these components malfunction or if communication between them is disrupted, the vehicle won’t start.
Using VCDS for Diagnostics
Once communication with the [05 – Acc/Start Auth.] controller is established, use VCDS to examine critical Measuring Value Blocks (MVBs):
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MVB-001 – Terminal Status: Indicates the current status of various power and ground connections.
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MVB-021 to 023 – Immobilizer Status: Provides information on the immobilizer system’s status and any related faults.
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MVB-025 & 153 – ESCL (Electric Steering Column Lock) Status: Shows the status of the steering column lock, helping diagnose potential issues with the N360.
Manually Applying Power
If you need to power up specific systems for testing, you can manually apply “Terminal 15” power (ignition-on power):
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Locate Relay: Identify the [J329 – Voltage Supply Terminal 15 (B+) Relay] typically located in the under-dash relay panel, often marked “370”.
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Jump Terminals: With the relay removed, carefully jump the two large terminals (30 and 87) to activate Terminal 15 power. Always consult the vehicle’s wiring diagram to confirm the correct relay and terminal locations before proceeding.
Conclusion
Troubleshooting an Audi with no keys requires understanding the vehicle’s starting logic and utilizing VCDS effectively. By waking up the CAN bus, accessing critical control modules, and interpreting the data provided by the MVBs, technicians can pinpoint the root cause of the “no start” condition and get the vehicle back on the road. Remember to always refer to official factory repair information and wiring diagrams for accurate and safe procedures.
