The RCD 300 radio unit in Volkswagen vehicles often requires coding changes via VCDS (Vag-Com Diagnostic System) to enable auxiliary (AUX) input. This article addresses a common issue encountered when attempting to activate the AUX function on a VW Golf MK5 with an RCD 300. We’ll explore various coding attempts and delve into potential solutions using VCDS.
Understanding the Problem: “NO CDC” Error
A frequent problem arises when trying to code the RCD 300 for AUX input: pressing the CD button results in a “NO CDC” message. This typically occurs after the factory CD changer plug at the rear of the RCD 300 has been replaced with an AUX cable. While seemingly straightforward, this modification often necessitates specific coding adjustments. The original coding might read as “0040402,” which displays the “NO CDC” error. Attempting to use coding “0040400” might be accepted by the system, but often doesn’t activate the desired AUX functionality. Furthermore, some coding attempts, like “0040401,” are outright rejected by the RCD 300.
Exploring VCDS Coding Options for the RCD 300
The challenge lies in finding the correct coding string to enable the AUX input while avoiding errors. Below is a breakdown of commonly tried codes:
- 0040402: This is often the original coding. It results in the “NO CDC” message when the CD button is pressed because the system is still looking for a CD changer.
- 0040400: This coding is often accepted by the system, but doesn’t necessarily enable the AUX input. It might represent a basic configuration without any additional features enabled.
- 0040401: The RCD 300 usually rejects this coding, indicating incompatibility with the desired configuration.
Troubleshooting with VCDS Diagnostic Logs
Using VCDS allows access to detailed diagnostic logs, which can offer clues to the underlying issue. A sample VCDS log provided shows a full vehicle scan, including the RCD 300 at Address 56. While the log indicates “No fault code found” for the radio, the coding “0040400” is noted. This suggests the coding might be the root cause of the AUX input problem. The log also highlights potential issues with other vehicle systems, which while unrelated to the radio issue, demonstrates the comprehensive diagnostic capabilities of VCDS. Examining the entire log can sometimes reveal interconnected problems. For example, a fault in the Central Electronics module (Address 09) related to under-voltage could potentially affect the operation of other components, including the radio.
Possible Solutions and Further Steps
- Consult RCD 300 Coding Documentation: Referencing official documentation or reputable online forums specific to the RCD 300 model and the Golf MK5 platform is crucial. This will help identify the correct coding for enabling AUX input after the CD changer modification.
- Verify AUX Cable Connection: Double-check the physical connection of the AUX cable to the rear of the RCD 300 to ensure it’s properly seated and wired correctly.
- Check for Software Updates: Outdated firmware in the RCD 300 can sometimes cause compatibility issues. Using VCDS, check for available software updates for the radio and apply them if necessary.
Conclusion: Finding the Right RCD 300 Code
Enabling AUX input on an RCD 300 after removing the CD changer often requires precise VCDS coding. While common codes like “0040400” might not work, thorough research and diagnostic log analysis are essential. Consulting official resources and verifying the physical connections are critical steps in troubleshooting this common issue. Using the comprehensive information provided by VCDS, combined with specific RCD 300 coding knowledge, is the key to successfully activating the AUX function on your VW Golf MK5.
