Network Termination
The Controller Area Network (CAN) uses network termination to improve communication reliability. Termination modules are located at both ends of the network. As network messages are broadcast in the form of voltage signals, the network voltage signals are stabilized by the termination resistors.
Each termination module has an internal 120 ohm resistor that bridges across the positive and negative bus connection. With two 120 ohm resistors located in a parallel circuit configuration, the total network impedance, or total resistance, is 60 ohms.
Network termination improves bus message reliability by
- stabilizing bus voltage.
- eliminating electrical interference.
Gateway Modules
The Instrument Panel Cluster (IPC) and Body Control Module (BCM) are gateway modules. The IPC translates messages on the HS-CAN to the I-CAN and vice versa. The BCM translates messages on the HS-CAN to the MS-CAN and vice versa. This allows a message to be distributed throughout all three networks.
The IPC and the BCM are the only modules on this vehicle that have this ability.
SPECIAL TOOLS CHART Fluke 77-IV Digital Multimeter FLU77-4 or equivalent Vehicle Communication Module (VCM) and Integrated Diagnostic System (IDS) software with appropriate hardware, or equivalent scan tool Flex Probe Kit NUD105-R025D or equivalent
Scheme 143
Scheme 144
Scheme 145
Controller Area Network (CAN) Fault Tolerance
Note. The oscilloscope traces below are from the Integrated Diagnostic System (IDS) oscilloscope taken using the IDS pre-configured CAN settings. The traces are for both data (+) and data (-) taken simultaneously (2-channel) at a sample rate of 1 mega-sample per second (1MS/s) or greater. Traces below are viewed at 500mV per division (vertical axis) and 20 microseconds (20μs) per division (horizontal axis). Readings taken with a different oscilloscope vary from those shown in illustration. Compare any suspect readings to a known good vehicle.
Scheme 146
The data (+) and data (-) circuits are each regulated to approximately 2.5 volts during neutral or rested network traffic. As messages are sent on the data (+) circuit, voltage is increased by approximately 1.0 volt. Inversely, the data (-) circuit is reduced by approximately 1.0 volt when a message is sent.
Successful communication of a message can usually be identified by the slight spike at the end of a message transmission. Any signals that are significantly different than the normal CAN waveform may cause network DTCs (U-codes) to set or may cause a complete network outage.
Scheme 147
In the event the data (+) and data (-) circuits become shorted together, the signal stays at base voltage (2.5V) continuously and all communication capabilities are lost.
Scheme 148
In the event the data (+) circuit becomes shorted to ground, both the data (+) and data (-) circuits are pulled low (0V) and all communication capabilities are lost.
Scheme 149
In the event the data (-) circuit becomes shorted to ground, the data (-) circuit is pulled low (0V) and the data (+) circuit reaches near-normal peak voltage (3.0V) during communication but falls to 0V instead of normal base voltage (2.5V). Communication may continue but at a degraded level.
Scheme 150
In the event the data (+) circuit becomes shorted to battery voltage, the data (+) circuit is pulled high (12V) and the data (-) circuit falls to abnormally high voltage (above 5V) during communication and reaches battery voltage (12V) for peak voltage. Communication may continue but at a degraded level.
Scheme 151
In the event the data (-) circuit becomes shorted to battery voltage, both the data (+) and data (-) circuits are pulled high (12V) and all communication capabilities are lost.
Scheme 152
Rhythmic oscillations, inductive spikes or random interference can corrupt the network communications. The corruption signal source may be outside electrical interference such as motors or solenoids or internal interference generated from a module on the network. In some cases, an open in either the data (+) or data (-) circuit to a network module may cause the module to emit interference on the one circuit which is still connected. The trace shown is an example of a "sawtooth" pattern transmitted from a module with one open network circuit.
Other corruptions may be present when a module is intermittently powered up and down. The module on power up may initiate communication out of sync with other modules on the network causing momentary communication outages.
Controller Area Network (CAN) Multiplex Messages
Note. Some HS-CAN faults may result in a no-start condition.
Note. For the I-CAN, message mapping is not essential to diagnostics as the symptoms arising from a message error are all related to the audio system. For audio system concerns, refer to INFORMATION AND ENTERTAINMENT SYSTEMS .
| Broadcast Message | Message Details | Originating Module | Network Type | Receiving Module(s) |
|---|---|---|---|---|
| A/C request | HVAC module | MS-CAN | BCM | |
| A/C request (gateway) | BCM | HS-CAN | PCM | |
| Acceleration data 1 | C-CM | HS-CAN | ABS module BCM IPC PCM RCM TCM | |
| Acceleration data 2 | C-CM | HS-CAN | ABS module BCM HUD module IPC PCM RCM IC | |
| Acceleration data 3 | C-CM | HS-CAN | BCM IPC | |
| Accelerometer data | Yaw rate data | RCM | HS-CAN | C-CM PCM PSCM TCM |
| Adaptive headlamp status | HCM | HS-CAN | IPC | |
| All wheel drive data | PCM | HS-CAN | ABS module IPC PCM TCM | |
| APIM data 3 | BCM | MS-CAN | HVAC module | |
| APIM personality data | APIM | HS-CAN | BCM C-CM IPC SCCM | |
| APIM personality data 2 | APIM | HS-CAN | BCM IPC | |
| APIM personality data 3 | APIM | HS-CAN | BCM IPC | |
| Battery management 1 | Actual current Alternator duty cycle Alternator fault Available current | PCM | HS-CAN | BCM |
| Battery management 2 | Battery low state-of-charge Idle speed increase request System status Voltage request | BCM | HS-CAN | IPC PCM PSCM SCCM |
| Battery management data (gateway) | BCM | MS-CAN | HSWM HVAC module | |
| BCM personality data | BCM | HS-CAN | APIM IPC | |
| BCM to HS-CAN body message (gateway) | Brake fluid level low status Brake warning indicator request DRL request Exterior lighting status Headlamp on warning command High beam indicator request Key-in-ignition warning command Park brake chime request | BCM | HS-CAN | FLM HCM IPC SCCM |
| BCM-to-body module information | Auto high beam command Battery saver status Brake fluid level low status Courtesy delay status Courtesy lamps status Courtesy mode status DRL status Fog lamp switch status Headlamp on warning Headlamp switch status High beam indicator request IKT program status Illuminated entry status Key-in-ignition warning Park brake warning chime request Stop lamps on status | BCM | MS-CAN | HVAC module RFA module |
| Body information 1 | Evaporator temperature Outside air temperature PATS indicator request Secondary heater request Vehicle lock status | BCM | HS-CAN | APIM ABS module C-CM FLM IPC PAM PCM SCCM TCM |
| Body information 2 | Accessory delay status Audio volume cutback Front passenger door ajar status Hood ajar status LR door ajar status RR door ajar status Tailgate ajar status | BCM | MS-CAN | APIM HVAC module RFA module LTM SOD-L SOD-R |
| Body information 2 (gateway) | BCM | HS-CAN | ABS module C-CM IPC SCCM | |
| Body information 3 | Drive range select status Ignition status Instrument panel illumination level Key-in-ignition status Left turn indicator command Park brake status Parklamp status Remote start warning request Right turn indicator command | BCM | HS-CAN | ABS module C-CM FLM IPC HCM HUD module PAM PCM SCCM |
| Body information 4 | Ambient air temperature Engine crank request Engine off status | BCM | HS-CAN | ABS module C-CM IPC PCM |
| Body information 6 | Administrator key total count Cross traffic alert Ignition key type MyKey key total count Side detect alert | BCM | HS-CAN | APIM C-CM IPC PCM RCM |
| Body information 7 | Accelerator pedal position Gear lever position Rear fog lamp status | BCM | MS-CAN | APIM DCSM HVAC RFA module SOD-L SOD-R |
| Body information status 3 | Day/night status Dimmer level Parklamp status Reverse lamp status Smart wiper motor status Turn signal status | BCM | MS-CAN | DCSM HSWM HVAC module SOD-L SOD-R |
| Body information status 5 | A/C compressor clutch status Cooling fan speed | BCM | MS-CAN | HVAC module |
| Body information status 6 | BCM | MS-CAN | APIM DSM GPSM LTM | |
| Brake sensor data 2 | Steering wheel sensor Stoplamp status | ABS module | HS-CAN | BCM C-CM HCM IPC PSCM PCM RCM |
| Brake sensor data 4 | Vehicle yaw rate sensor Total brake torque request | ABS module | HS-CAN | BCM C-CM IPC PCM TCM |
| Brake system data 1 | ABS indicator lamp request Brake chime request Hill descent status Parking brake lamp request Vehicle active braking status | ABS module | HS-CAN | RCM IPC C-CM PCM PAM TCM |
| Brake system data 2 | ABS module | HS-CAN | C-CM IPC PCM | |
| C-CM personality data | C-CM | HS-CAN | APIM IPC | |
| Centerstack personality data | BCM | MS-CAN | DSM HVAC module RFA module | |
| Climate control data | Ambient temperature Engine idle increment Estimate recirculation percentage Estimated airflow In-car temperature Outside air temperature Remote start quiet mode Secondary heater request | HVAC module | MS-CAN | BCM |
| Climate control seat command (gateway) | Drivers seat command Passenger seat command | BCM | MS-CAN | DCSM |
| Climate control seat command (gateway) | Drivers seat command Passenger seat command | IPC | HS-CAN | BCM |
| Climate control seat request | BCM | MS-CAN | HVAC module | |
| Climate control seat request (gateway) | IPC | HS-CAN | BCM | |
| Climate control seat status | Drivers seat status Passenger seat status | DCSM | MS-CAN | BCM |
| Climate control seat status (gateway) | Drivers seat status Passenger seat status | BCM | HS-CAN | IPC |
| Climate control seat temperature setting (gateway) | BCM | HS-CAN | IPC | |
| Climate control status | Front system mode request Rear defrost request Rear system mode request | HVAC module | MS-CAN | BCM |
| Climate control status (gateway) | BCM | HS-CAN | IPC | |
| Cross traffic warning command | IPC | HS-CAN | BCM | |
| Desired brake torque | ABS activation Stability control brake activation | ABS module | HS-CAN | PCM BCM C-CM TCM PAM RCM |
| Driver memory seat feedback request | DSM | MS-CAN | BCM | |
| Driver seat module memory data | DSM | MS-CAN | BCM | |
| Driver seat status | Easy entry request | DSM | MS-CAN | BCM |
| DSM personality data | BCM | HS-CAN | APIM IPC | |
| ECall confirmation | APIM | HS-CAN | BCM RCM | |
| Engine brake data | PCM | HS-CAN | APIM ABS module BCM C-CM IPC OCS RCM SCCM TCM | |
| Engine data | Engine speed Fuel level Vehicle speed | BCM | MS-CAN | APIM HVAC LTM |
| Engine data 1 | IPC gear display IPC mode display | PCM TCM | HS-CAN | IPC |
| Engine data 13 | Speed limiter request | PCM | HS-CAN | TCM |
| Engine data 2 (gateway) | Engine status | BCM | MS-CAN | APIM GPSM HSWM HVAC module RFA module SOD-R SOD-L |
| Engine data 3 | PCM | HS-CAN | BCM IPC TCM | |
| Engine data 4 | PCM | HS-CAN | TCM | |
| Engine data 6 | Engine over-heat mitigation | PCM | HS-CAN | BCM IPC TCM |
| Engine data 7 | Air conditioning clutch status Air conditioning request Ambient air temperature Engine oil life status Engine service required status Fuel fill inlet status Odometer count | PCM | HS-CAN | BCM IPC PAM RCM TCM |
| Engine data 8 | PCM | HS-CAN | TCM | |
| Engine torque data flags | Brake on/off switch status Wheel torque data | PCM | HS-CAN | ABS module BCM C-CM IPC OCS RCM TCM |
| EPAS information | EPAS fault Steering angle Steering column torque | PSCM | HS-CAN | ABS module BCM IPC PAM |
| FDIM information status | Compass display data Rear vision camera display status Segment display data | BCM | HS-CAN | ABS module APIM IPC |
| Four wheel drive information 1 | PCM | HS-CAN | ABS module IPC | |
| GPS heading/speed data | GPSM | MS-CAN | APIM | |
| GPS location data | GPS latitude GPS longitude | GPSM | MS-CAN | APIM |
| GPS time/date data | GPSM | MS-CAN | APIM BCM | |
| Heads up display status | HUD module | HS-CAN | C-CM | |
| Heated steering wheel status | HSWM | MS-CAN | BCM | |
| HVAC personality data | HVAC module | MS-CAN | BCM | |
| HVAC personality data (gateway) | BCM | HS-CAN | APIM IPC | |
| Ignition switch data | Brake pedal position switch status Ignition status Key-in-ignition status Remote start status Remote device status | BCM | MS-CAN | APIM DSM GPSM HSWM HVAC module IPC LTM RFA module SOD-L SOD-R |
| IPC information 1 | Auto high beam command Engine oil life reset request English/metric units ePRNDL mode Odometer master value MyKey data | IPC | HS-CAN | APIM ABS module BCM C-CM PCM TCM |
| IPC information 3 | Belt-Minder® warning status Fuel level Fuel level sensor data | IPC | HS-CAN | APIM BCM PCM |
| IPC personality data 1 | IPC | HS-CAN | APIM BCM C-CM SCCM | |
| IPC personality data 2 | IPC | HS-CAN | APIM | |
| Keyless entry keypad data | Button press Power liftgate request | BCM | MS-CAN | LTM RFA module |
| Message center personality data | Autolamp delay status Keycode status | BCM | MS-CAN | DSM HVAC module RFA module |
| Message center status | Autolamp delay status Keycode status PEPS status | BCM | HS-CAN | IPC PCM |
| Navigation rolling wheel count | BCM | MS-CAN | GPSM | |
| OCS information | OCS | HS-CAN | BCM IPC RCM | |
| Parking aid data | PAM | HS-CAN | PSCM | |
| Parking aid range to target | PAM | HS-CAN | BCM | |
| Parking aid sounder command | PAM | HS-CAN | BCM IPC | |
| Parking aid sounder status | IPC | HS-CAN | PAM | |
| Passive entry control data | RFA module | MS-CAN | BCM | |
| Passive entry target data | BCM | MS-CAN | RFA module | |
| PATS control information 1 | BCM | HS-CAN | PCM | |
| PATS target information 1 | PCM | HS-CAN | BCM | |
| Perimeter alarm chime request | Courtesy delay status Courtesy lamps mode | BCM | HS-CAN | IPC |
| Power liftgate status | LTM | MS-CAN | BCM | |
| Powertrain data 1 | Fuel alcohol percentage data Oil pressure warning status Vehicle speed limit data | PCM | HS-CAN | BCM IPC RCM TCM |
| Powertrain data 2 | Accelerator pedal position data Calculated engine load Engine air intake temperature data Engine coolant temperature data | PCM | HS-CAN | BCM IPC TCM |
| RCM serial number | RCM | HS-CAN | ABS module OCS | |
| RCM status | Beltminder® warning status eCall notification Fuel cutoff request Restraint event triggered Seat belt indicator request | RCM | HS-CAN | APIM BCM C-CM IPC OCS PCM |
| Remote start status | BCM | HS-CAN | IPC | |
| Restraints data | Passenger restraint indicator status Seat belt indicator status Seat belt warning chime status | IPC | HS-CAN | RCM |
| RFA personality data | RFA module | MS-CAN | BCM | |
| RFA personality data (gateway) | BCM | HS-CAN | APIM IPC | |
| SCCM personality data | SCCM | HS-CAN | APIM IPC | |
| Side detect status left | SOD-L | HS-CAN | BCM SOD-R | |
| Side detect status right | SOD-R | HS-CAN | BCM SOD-L | |
| Smart headlamps status | Dimmer switch status Fog lamp status Headlamp switch status | FLM | HS-CAN | BCM |
| Steering data | Audio steering wheel control data Flash-to-pass status Smart wiper motor status Turn signal status | SCCM | HS-CAN | BCM C-CM IPC PCM PAM |
| Steering wheel data | PSCM SCCM | HS-CAN | ABS module BCM C-CM PCM PAM SCCM PSCM | |
| Steering wheel data (gateway) | Yaw sensor data | BCM | MS-CAN | DSM GPSM |
| Steering wheel data 2 | Message center button status | SCCM | HS-CAN | IPC |
| Throttle position | PCM | HS-CAN | ABS module BCM C-CM HCM IPC OCS PAM PSCM RCM SCCM TCM | |
| Tire pressure data | BCM | HS-CAN | APIM IPC PSCM | |
| Tire pressure status | BCM | HS-CAN | APIM IPC | |
| Traction control status | ABS module | HS-CAN | C-CM PAM PCM RCM TCM | |
| Transmission data 1 | TCM | HS-CAN | PCM | |
| Transmission data 2 | Commanded gear position | TCM | HS-CAN | PCM |
| Transmission data 3 | Idle speed increase request Overdrive cancel indicator status | TCM | HS-CAN | PCM |
| Transmission gear data 1 | Gear position Transmission fluid level Transmission shift mode | TCM | HS-CAN | ABS module BCM C-CM IPC SCCM HCM RCM OCS PAM |
| Transmission gear data 2 | Transmission MIL request | TCM | HS-CAN | PCM |
| Transmission gear data 3 | Gear engagement data | TCM | HS-CAN | PCM |
| Vehicle emergency data 1 | Air bag status eCall notification Seat belt status | RCM | HS-CAN | APIM |
| Vehicle entry request | RFA module | MS-CAN | BCM LTM | |
| Vehicle lock status | BCM | MS-CAN | RFA module | |
| Wheel data | Wheel rotation direction | ABS module | HS-CAN | C-CM IPC PAM PSCM PCM TCM |
| Wheel speed | Left front wheel speed Left rear wheel speed Right front wheel speed Right rear wheel speed | ABS module | HS-CAN | C-CM PAM PSCM PCM TCM |
| Yaw data | RCM | HS-CAN | BCM C-CM PCM TCM |
CONTROLLER AREA NETWORK (CAN) MODULE COMMUNICATION MESSAGE CHART