2010 Cadillac Truck SRX FWD V6-3.0L Page 2163
Note: Each control module may need to be disconnected to isolate a circuit fault. Use the schematic to identify the following:
* Control modules the vehicle is equipped with
* Mid speed or chassis high speed serial data circuit terminating resistors
* Control module locations on the serial data circuits
* Each control modules mid speed or chassis high speed serial data circuit terminals
1. Attempt to communicate with all control modules on the mid speed or chassis high speed serial data circuit. Refer to Data Link References (
See: Powertrain Management/Computers and Control Systems/Information Bus/Testing and Inspection/Initial Inspection and Diagnostic
Overview). Communications should not be available with two or more control modules on the mid speed or chassis high speed serial data
circuit.
瀚慖f only one control module is not communicating, diagnose that control module only. Refer to DTC U0100-U02FF (See: U Code
Charts/U0100).
2. Disconnect the scan tool from the DLC. The following tests will be done at the DLC connector.
3. All access doors closed, ignition OFF for 60 seconds, test for less than 10 ohm between the ground circuit terminal 5 and ground.
瀚慖f greater than the specified range, test the ground circuit for an open/high resistance.
4. Ignition ON, test for less than 3 V between the serial data circuits listed below and ground:
* Mid speed GMLAN serial data terminal 3
* Mid speed GMLAN serial data terminal 11
* Chassis high speed GMLAN serial data terminal 12
* Chassis high speed GMLAN serial data terminal 13
瀚慖f greater than the specified range, test the serial data circuit for a short to voltage. Refer to Testing the Serial Data Circuits for a Short to
Voltage.
5. Ignition OFF for 60 seconds, test for greater than 100 ohm between the serial data circuits listed below and ground:
* Mid speed GMLAN serial data terminal 3
* Mid speed GMLAN serial data terminal 11
* Chassis high speed GMLAN serial data terminal 12
* Chassis high speed GMLAN serial data terminal 13
瀚慖f not the specified value, test the serial data circuit for a short to ground. Refer to Testing the Serial Data Circuits for a Short to ground.
6. Test for 50-70 ohm between the serial data circuits listed below:
* Mid speed GMLAN serial data circuits terminal 3 and terminal 11
* Chassis high speed GMLAN serial data circuits terminal 12 and terminal 13
瀚慖f less than 35 ohm, test for a short between the serial data circuits. Refer to Testing the Serial Data Circuits for a Short between the
Circuits.
瀚慖f 35-50 ohm there may be a third terminating resistor between the serial data circuits. This can happen if the incorrect control module is
installed. Some control modules are available with and without the terminating resistors installed to reduce the need of terminating
resistors in the wiring harness.
瀚慖f greater than 70 ohm but less than infinite, test the serial data circuit for an open/high resistance. Refer to Testing the Serial Data
Circuits for an Open/High Resistance.
瀚慖f infinite, test the serial data circuits between the DLC and the first connection to the serial data circuit for an open/high resistance.
7. If the circuits test normal, refer to Testing the Ignition Circuit.
Testing the Serial Data Circuits for a Short to Voltage
1. Ignition OFF, disconnect the harness connectors with the mid speed or chassis high speed serial data circuits at an easily accessible control
module.
2. Ignition ON, test for greater than 3 V between the serial data circuits and ground. Verify that one or more serial data circuits are greater than
3 V.
瀚慖f less than the specified range for all serial data circuits, replace the control module that was disconnected.
3. Ignition OFF, disconnect the harness connectors with the mid speed or chassis high speed serial data circuits at another control module, in the
direction of the circuit shorted to voltage.
4. Ignition ON, test for greater than 3 V between the serial data circuits and ground. Verify that one or more serial data circuits are greater than
3 V.
瀚慖f less than the specified range for all serial data circuits, replace the control module that was just disconnected.
