COMMUNICATIONS NETWORK
See the SYSTEM WIRING DIAGRAMS for schematic information.
Network Termination
The CAN uses a network termination circuit to improve communication reliability. The network termination of the CAN bus takes place inside the termination modules by termination resistors. Termination modules are located at either end of the bus 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 a 120 ohm resistor across the positive and negative bus connection in the termination module. With 2 termination modules on each network, and the 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 Module
The instrument cluster (IC) is the gateway module, translating HS-CAN to MS-CAN and vice versa. This information allows a message to be distributed throughout both networks. The IC is the only module on this vehicle that has this ability.
MS-CAN
The MS-CAN uses an unshielded twisted pair cable of data (+) and data (-) circuits. The data (+) and the data (-) circuits are each regulated to approximately 2.5 volts during neutral or rested network traffic. As bus 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 bus message is sent. Multiple bus messages can be sent over the CAN circuits allowing multiple modules to communicate with each other. The MS-CAN is used for the IC and the smart junction box (SJB) communications, and is designed for general information transfer. The MS-CAN will not communicate while certain faults are present, but will operate with diminished performance with other faults present. The MS-CAN bus may remain operational when 1 of the 2 termination resistors are not present.
The MS-CAN operates at a maximum data transfer speed of 125 Kbps for bus messages and is designed for general information transfer. The network will remain operational, but at a degraded level when certain circuit faults are present.
The following fault chart describes the specific MS-CAN failures and their resulting symptom
MS-CAN Communication Fault Chart
| Failure Description | Symptom |
|---|---|
| MS-CAN (+) shorted to MS-CAN (-) | No communication |
| MS-CAN (+) short to voltage | No communication |
| MS-CAN (-) short to voltage | No communication |
| MS-CAN (+) short to ground | No communication |
| MS-CAN (-) short to ground | Unreliable communication |
| MS-CAN (+) open | Unreliable communication |
| MS-CAN (-) open | Unreliable communication |
| Module loss of voltage or ground | No communication |
| Module internal failure | No communication |
MS-CAN COMMUNICATION FAULT CHART
HS-CAN
The HS-CAN uses an unshielded twisted pair cable of data (+) and data (-) circuits. The data (+) and the data (-) circuits are each regulated to approximately 2.5 volts during neutral or rested network traffic. As bus 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 bus message is sent. Multiple bus messages can be sent over the CAN circuits allowing multiple modules to communicate with each other. The HS-CAN is a high speed communication network used for the IC, the PCM, the ABS module, and 4X4 control module communications, and designed for real time information transfer and control. The HS-CAN will not communicate while certain faults are present, but will operate with diminished performance with other faults present. The HS-CAN bus may remain operational when 1 of the 2 termination resistors are not present.
The HS-CAN operates at a maximum data transfer speed of 500 Kbps and is designed for real time information transfer and control. The network will remain operational, but at a degraded level when certain circuit faults are present.
The following fault chart describes the specific HS-CAN failures and their resulting symptom
HS-CAN Communication Fault Chart
| Failure Description | Symptom |
|---|---|
| HS-CAN (+) shorted to HS-CAN (-) | No communication |
| HS-CAN (+) short to voltage | No communication |
| HS-CAN (-) short to voltage | No communication |
| HS-CAN (+) short to ground | No communication |
| HS-CAN (-) short to ground | Unreliable communication |
| HS-CAN (+) open | Unreliable communication |
| HS-CAN (-) open | Unreliable communication |
| Module loss of voltage or ground | No communication |
| Module internal failure | No communication |
HS-CAN COMMUNICATION FAULT CHART
Module Communication Message Charts
The following charts describes the specific CAN messages broadcast by each module, and the module(s) that receive the message
CAN Module Communication Message Chart
| Broadcast Message | Originating Module | Network Type | Receiving Module(s) |
|---|---|---|---|
| ABS/trac event in progress | ABS module | HS-CAN | RCM |
| ABS/trac malfunction indicator on request | ABS module | HS-CAN | IC |
| A/C clutch request | HVAC module | MS-CAN | IC |
| A/C clutch request (gateway) | IC | HS-CAN | PCM |
| A/C clutch status | PCM | HS-CAN | IC |
| A/C clutch status (gateway) | IC | MS-CAN | HVAC module |
| Accelerator pedal position | PCM | HS-CAN | 4X4 control module |
| Accessory delay status | SJB | MS-CAN | ACM FCIM FDIM |
| Airbag warning indicator request | RCM | HS-CAN | IC |
| Airbag warning indicator status | IC | HS-CAN | RCM |
| Ambient temperature | HVAC module | MS-CAN | FDIM IC |
| Autolamp delay time | IC | MS-CAN | SJB |
| Barometric pressure | PCM | HS-CAN | IC |
| Barometric pressure (gateway) | IC | MS-CAN | HVAC module SJB |
| Brake fluid level status | SJB | MS-CAN | IC |
| Brake (red) warning indicator request | ABS module | HS-CAN | IC |
| Brake (red) warning indicator request | SJB | MS-CAN | IC |
| Brake speed control deactivator switch status | ABS module | HS-CAN | PCM |
| Brake switch status | PCM | HS-CAN | ABS module 4X4 control module |
| Charging system warning indicator request | PCM | HS-CAN | IC PSCM |
| Clutch pedal position | PCM | HS-CAN | ABS module |
| Climate control fan setting display data | HVAC module | MS-CAN | FDIM |
| Climate control temperature display data | HVAC module | MS-CAN | FDIM |
| Clutch pedal position | PCM | HS-CAN | ABS module |
| Compass data | IC | MS-CAN | FDIM |
| Door ajar status | SJB | MS-CAN | IC |
| Door ajar status (gateway) | IC | HS-CAN | ABS module |
| Door autolock command | IC | MS-CAN | SJB |
| Door autolock status | SJB | MS-CAN | IC |
| Door auto unlock command | IC | MS-CAN | SJB |
| Door auto unlock status | SJB | MS-CAN | IC |
| Drivetrain type | PCM | HS-CAN | ABS module IC |
| Engine coolant temperature | PCM | HS-CAN | IC 4X4 control module |
| Engine coolant temperature (gateway) | IC | MS-CAN | HVAC module |
| Engine failsafe electronic throttle control (ETC) status | PCM | HS-CAN | IC |
| Engine fuel flow data | PCM | HS-CAN | IC |
| Engine malfunction indicator lamp (MIL) request | PCM | HS-CAN | IC |
| Engine off timer | PCM | HS-CAN | IC 4X4 control module |
| Engine off timer (gateway) | IC | MS-CAN | HVAC module |
| Engine RPM | PCM | HS-CAN | ABS module IC PSCM 4X4 control module |
| Engine RPM (gateway) | IC | MS-CAN | HVAC module |
| Engine torque data | PCM | HS-CAN | ABS module |
| Engine torque reduction request | ABS module | HS-CAN | PCM |
| Engine torque transfer data | ABS module | HS-CAN | 4X4 control module |
| English/metric display mode | IC | MS-CAN | ACM HVAC module |
| Failsafe cooling mode status | PCM | HS-CAN | IC |
| Fuel cap off indicator request | PCM | HS-CAN | ABS module IC 4X4 control module |
| Fuel level input status (instant) | IC | HS-CAN | PCM |
| Headlamp high beam indicator request | SJB | MS-CAN | IC |
| Headlamps on warning request | SJB | MS-CAN | IC |
| Ignition switch position | SJB | MS-CAN | ACM HVAC module FCIM FDIM IC |
| Ignition switch position (gateway) | IC | HS-CAN | ABS module PCM PSCM 4X4 control module |
| Illumination dimmer level | SJB | MS-CAN | ACM FCIM FDIM HVAC module IC |
| Integrated keyhead transmitter (IKT) program request | IC | MS-CAN | SJB |
| IKT data | IC | MS-CAN | SJB |
| IKT response | SJB | MS-CAN | IC |
| Key-in-ignition warning request | SJB | MS-CAN | IC |
| Navigation rolling wheel count | ABS module | HS-CAN | IC |
| Navigation rolling wheel count (gateway) | IC | MS-CAN | ACM |
| OCS Data | OCSM | HS-CAN | RCM |
| OCS system fault status | OCSM | HS-CAN | RCM |
| Odometer count | ABS module | HS-CAN | IC |
| Odometer low status | IC | MS-CAN | HVAC module SJB |
| Parking brake status | SJB | MS-CAN | IC |
| Parking brake status (gateway) | IC | HS-CAN | 4X4 control module PCM |
| Passive anti-theft system (PATS) security data | PCM | HS-CAN | IC |
| PATS security data | IC | HS-CAN | PCM |
| PATS status | PCM | HS-CAN | IC |
| PATS status | IC | MS-CAN | SJB |
| PSCM status | PSCM | HS-CAN | IC |
| Power steering current draw | PSCM | HS-CAN | ABS module |
| RCM event data | RCM | HS-CAN | IC OCSM PCM |
| RCM serial number | RCM | HS-CAN | ABS module OCSM |
| Restraints event data record | PCM | HS-CAN | RCM |
| Safety belt chime/flash request | RCM | HS-CAN | IC |
| Safety belt indicator status | IC | HS-CAN | RCM |
| Safety belt indicator request | RCM | HS-CAN | IC |
| Safety belt latched status | RCM | HS-CAN | OCSM |
| Safety Belt-Minder® chime status | IC | HS-CAN | RCM |
| Speed control status | PCM | HS-CAN | IC 4X4 control module |
| Stability control warning indicator request | ABS module | HS-CAN | IC |
| Steering wheel angle | PSCM | HS-CAN | ABS module 4X4 control module |
| Throttle position | PCM | HS-CAN | ABS module |
| Tire pressure monitor system (TPMS) system status | SJB | MS-CAN | IC |
| TPMS warning indicator request | SJB | MS-CAN | IC |
| Tire size information | ABS module | HS-CAN | PCM |
| Traction control event in progress | ABS module | HS-CAN | PCM RCM |
| Transaxle warning indicator request | PCM | HS-CAN | IC |
| Transaxle overdrive indicator request | PCM | HS-CAN | IC |
| Transaxle selector (PRNDL) range | PCM | HS-CAN | ABS module IC |
| Transaxle selector (PRNDL) range (gateway) | IC | MS-CAN | ACM SJB |
| Transaxle shift in progress | PCM | HS-CAN | ABS module |
| Turn signal indicator request | SJB | MS-CAN | IC |
| Vehicle speed | ABS module | HS-CAN | IC PSCM RCM OCSM |
| Vehicle speed (gateway) | IC | MS-CAN | ACM HVAC module SJB |
| VIN information | PCM | HS-CAN | ABS module IC OCSM RCM 4X4 control module |
| VIN information (gateway) | IC | MS-CAN | ACM HVAC module SDARS module SJB |
| Wheel speed output (RF, LF, RR, LR) | ABS module | HS-CAN | PCM 4X4 control module |
| 4X4 coupling mode and status | 4X4 control module | HS-CAN | ABS module |
| 4X4 engaged indicator request | 4X4 control module | HS-CAN | IC |
| 4X4 malfunction indicator request | 4X4 control module | HS-CAN | IC |
CAN MODULE COMMUNICATION MESSAGE CHART
Possible Causes
- Output circuit short to ground or voltage
- SJB
- Charging system concern
- SJB
- Output circuit short to ground or voltage
- SJB
- Module communication
- IC