Theory Of Operation

The Radio/Entertainment Telematics Module (ETM) manages the radio, hands-free, navigation, and satellite functions of the vehicle. The ETM becomes operational after receiving a wake up signal over the CAN-IHS data bus indicating the status of the ignition switch is On. Depending upon audio system options, the ETM can play audio from many different media sources, such as the 3.5 millimeter auxiliary (AUX) port, a universal serial bus (USB) port or through wireless Bluetooth™ audio streaming. The ETM uses a roof mounted antenna for AM/FM signal reception; and depending upon optional equipment, a roof mounted combination antenna that can receive global positioning system (GPS) and satellite radio signals

The EMCM control knob operates the radio functions, as well as select between different features of the multimedia system. Both the volume and EMCM control knobs operate based on customer action; which can be twisted, shifted in all four directions, or pressed. The volume control knob connects to the EMCM through a LIN connection, where the module is the main, or master. There is also a separate circuit to control knob backlight, which is at the base of the knob. The EMCM connects to the CAN-IHS bus; and communicates separately, the customer volume input request signal to the ETM.

There are two different audio speaker system configurations:

• Base - (Sales Code - RCH) a component system that uses a separate woofer and tweeter for each corner of the passenger compartment.
• Premium (Sales Code - RCA) utilizes the same speaker combination as the Base, but adds four mid-range speakers: one in each front door near the woofer, and two on the rear shelf next to the subwoofer to support a surround-sound effect.

The speakers (mid-range and woofer) are manufactured from different components, depending on the level of the audio system. Make sure any serviced speakers are similar to the one being removed. The Premium include an external Amplifier mounted in the left side of the trunk. The Premium system uses a 12-channel Amplifier. The ETM uses the vehicle build configuration data to determine whether the vehicle is equipped with an external or internal Amplifier. If the vehicle is identified as one utilizing a separate Amplifier, the ETM sets two of the channels at a set output and disables the remaining speaker outputs. These circuits feed into the Amplifier as audio inputs. Any changes to balance or fade is commanded from the ETM to the Amplifier via the Controller Area Network (CAN) bus.

Courtesy of CHRYSLER GROUP, LLC