This article explores troubleshooting a Volkswagen Jetta’s alarm horn not sounding when locking the car using VCDS diagnostics. We’ll examine the process of replacing the Comfort Control Module (CCM) and diagnosing the issue with a new module.
CCM Replacement and Diagnosis
The original CCM, component number starting with 4B, was replaced with a spare unit from a 2002 Bora V5 Trendline with component number starting with 2K. While the connection seemed stable with the replacement CCM, occasional garbled green text still appeared in VCDS.
An output test using VCDS showed a test for the Alarm Horn (H12). Although an audible click could be heard from the CCM during the test, the alarm horn itself did not sound.
Further diagnostics revealed a new fault code:
The code indicated an “Alarm horn (H12) Unknown switch condition.” This code had not been present with the original CCM. Additionally, the Alarm Sources in the new CCM displayed different codes than the original (all 255).
Despite the donor Bora having similar specifications and options to the Jetta, subtle differences existed, including the year, engine type (V5 vs. TDI), and color code.
An attempt to measure current draw with a multimeter after a five-minute rest period failed due to a faulty multimeter. However, the voltage remained steady at 12.97 volts after locking the car and throughout the five-minute period.
Conclusion
Despite replacing the CCM, the alarm horn on the Jetta still did not function when locking. The new CCM presented a new fault code related to the alarm horn, suggesting a potential wiring or configuration issue. Further diagnosis is required to pinpoint the exact cause of the malfunction. The next step involves investigating the wiring harness and checking for any potential breaks or shorts in the alarm horn circuit.
