How to Properly Test Analog Steering Wheel Controls

How to tell if your vehicle uses an Analog Steering Wheel Control circuit

When consulting the wiring guide for your steering wheel control interface, whether it be a SWI-RC-1 / SWI-CP2 / CP5, C4RAD, SC4RAD or SWI-RC, they will all use the same wire colors when wiring into these systems. 

The SWI's use the same 4 wires for these circuits. 

White - 3.3Volt Analog 1

White/Black- 3.3Volt Analog 2

White/Red - 3.3Volt Analog 3

Green - 12Volt Analog 4

If your vehicle wiring guide shows any of these wires or a combination of the three, it lets you know that it's an analog-based system.

Link to Guides: 

SWI-CP2 / SWI-CP5 : https://pac-audio.com/pages/swi/cp-2_5

SWI-RC-1: https://pac-audio.com/pages/swi/rc-1

SWI-RC: https://pac-audio.com/pages/swi/rc

Once you have found that your system is an analog circuit, review the following steps below to understand how to troubleshoot problems and properly test the circuit.

How to test the Analog Circuit with a Multi-Meter

You will need a Multi-Meter that can measure resistance indicated by this symbol. Ω

Picture for example:

Note the section in yellow with the various range settings. This is where you will need to set the meter. If the meter is not auto ranging, 2000 Ω is the best place to start.

Once you have a meter with this feature and determined that your vehicle is analog and is giving you issues with programming your SWI interface here are some proper steps to take.

1. Disconnect the SWC Interface from the plug. You cannot test the SWC circuit with the module connected.
2. Place your positive (red) probe on the first Analog Channel. Typically the white wire coming from the SWI interface. If you were instructed to connect a wire to 12v in the wiring guide, connect the red probe to this wire.
3. Ground the negative probe to the wire you were instructed to ground in the wiring guide. You can also use one of the black wires from the SWI interface as long as you connected it to the wire you were instructed to ground. If you were not instructed to ground a wire, then you can just use the radio ground. If you were instructed to connect a wire to 12v in the wiring guide, use the radio ground.
4. Press and hold the Volume Up button on the steering wheel and look for a response on the meter. Note that not all buttons are on the same channel. 

Example of a Nissan.

Note that the values are the same from channel to channel. This is the purpose of having two channels as you cant have two buttons with the same value on one channel, or you would have incorrect outputs based on what button you're pressing.

Record your values / faults and address the issue. If you are not getting any kind of reading then you are on the wrong wire. Remember that pin position is more important than wire color. If you are getting readings on all buttons but the module is not responding, the only option is to go the manual mapping route. That procedure is outlined in this article: https://pacaudio.zendesk.com/hc/en-us/articles/37430194578317-Manually-Programming-a-Steering-Wheel-Control-Module

Here is a video demonstrating everything covered in this article: