Shown below is a 2008 Toyota Tacoma truck bus network diagram for the DLC connector. To test NO COMMUNICATION fault message from your scanner, please use this simple method as your guide. Using a digital voltmeter, you can prevent garages from charging you expensive rates to troubleshoot this truck.
The 2 high speed buses are seen here by red arrows with bus wires having yellow and violet colors. High speed CAN bus wires are usually wired in pairs and end with terminating resistors (R) at the bottom left junction connectors. Also, the low speed buses like SIL (brown) and TC (orange) are connected as a stand alone bus wire to the modules.
2008 Toyota Tacoma Truck Bus Network Description:
This bus wiring diagram is almost similar to the 2005 model. I have omitted the tire pressure monitor to simplify it. To avoid confusion, please focus to the flow of the DLC pin terminals especially the CAN High and CAN LO bus wires.
Looking at the DLC connections from PIN 1 to PIN 16, the only important PINS you need for troubleshooting are:
PIN 4 which connects to the battery ground
PIN 5 which connects to the sensor ground
PIN 6 which supplies the CAN Hi speed bus data communication
PIN 7 which supplies SIL low speed bus data communication
PIN 9 which supplies TAC low speed bus data communication
PIN 12 which supplies TS low speed bus data communication
PIN 13 which supplies TC low speed bus data communication
PIN 14 which supplies CAN LO (hi speed) data cmmunication
PIN 16 which supplies battery power
DLC terminal pins 7, 9, 12, 13 and 15 are all low speed bus network which I have discussed extensively in earlier 2003 Toyota Tacoma communication model. It is worth mentioning here that when testing low speed bus data voltage, expect to get 7 volts at key on engine off (KOEO). However, when testing high speed bus data voltage like PIN 6 and PIN 14 (when measured against PIN 5 as ground), expect to get a fluctuating 1.5 volts-3.5 volts or an average of 2.5 volts at KOEO. If you can remember this and understand this simple bus wiring connections to the DLC, you can manage to repair NO COMMUNICATION problems on your 2008 Toyota vehicles.
Troubleshooting 2008 Toyota Tacoma bus network:
The same voltage test used on 2005 Ford F150 and GM hybrid trucks apply. However, you can use the resistance setting of the voltmeter to probe DLC pins 6 and 14. With key off, put the ohmmeter leads at DLC pins 6 and 14. Between those 2 DLC pins, you should get 60 ohms. If you get over or lower than 60 ohms, it means one of the modules is defective. Note also that if the resistance reading goes to 120 ohms, it show that the terminating resistors are open or not connected if one of the bus module has failed. To verify, use the voltmeter setting and measure the voltage of each DLC pins 6 and 14. When measured against DLC pin 5, you should get a fluctuating 1.5 to 3.5 volts at KOEO.
To test the high speed communication to ECM module in the middle top, use DLC pin 6 to measure 2.5 to 3.5 volts as your guide range at KOEO. Disconnect the red dot connector at ECM module to isolate the high speed CAN High bus circuit. Lower or higher than given range means a defect in the ECM module. To test CAN Lo bus circuit, measure the voltage at DLC Pin 14 and use 1.5 to 2.5 volts as your guide at KOEO. To isolate the CAN Lo signal at Skid Control ECU module shown in middle side right, disconnect the green dot connector.
The actual bus network diagram will show you the exact colors of the bus wires and locations of the modules in the circuit.
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