Understanding the wiring diagram for steering wheel control keys, specifically Key 1 and Key 2 wires, is crucial for troubleshooting common head unit issues. This article delves into a specific problem with a Joying/Funrover head unit in a 2012 Ford Focus Titanium, exploring potential solutions and common pitfalls.
The problem stems from the head unit misinterpreting steering wheel control button presses. While the buttons are recognized by the head unit’s software, the resistance values registered are significantly lower than expected. The SWC app displays resistance values hovering around 30 ohms by default. Pressing a button only slightly alters this value to around 16 or 20 ohms. This contrasts sharply with the head unit manual, which indicates expected resistance values in the hundreds.
Testing reveals that the car’s steering wheel control wiring is functioning correctly. A multimeter connected directly to the car’s wires shows expected resistance values ranging from 250 to 1500 ohms, confirming the issue lies within the head unit’s interpretation of these signals. Further attempts to simulate the steering wheel buttons using an Arduino with varying resistors also failed to produce readings above 30 ohms, regardless of whether Key 1 or Key 2 wire was used. Even an aftermarket SWC interface designed to amplify resistance signals proved ineffective.
Exploring the head unit’s settings revealed that changing the car model and CanBox settings had some impact on the baseline resistance values. However, achieving the expected base level of 256 ohms, as indicated in the manuals for other car models, remains elusive. The current base level sits at 30 ohms even without the Key and Ground wires connected.
The core issue appears to lie in a mismatch between the expected impedance of the head unit and the actual resistance values received from the steering wheel control. Potential solutions might involve modifying the head unit’s impedance or finding a compatible CanBox decoder specifically designed for the 2012 Ford Focus Titanium’s steering wheel control system. Further investigation into the head unit’s firmware and hardware specifications might be necessary to pinpoint the exact cause of this discrepancy and identify a suitable solution.
