2010 Cadillac CTS Sedan AWD V6-3.6L Page 2050
Scan Tool Reference
Control Module References (See: Testing and Inspection/Programming and Relearning) for scan tool information
Circuit/System Verification
1. Determine the control module that is not communicating. Refer to Control Module U Code List (See: Diagnostic Trouble Code
Descriptions/Control Module U Code List).
2. Verify that DTC U1814, U2099, B1428, B1370, B1380, B1440, or B1441 is not set.
瀚慖f any of the DTCs are set, refer to Diagnostic Trouble Code (DTC) List - Vehicle (See: Diagnostic Trouble Code
Descriptions/Diagnostic Trouble Code (DTC) List - Vehicle).
3. Engine running for 10 seconds.
4. Ignition ON, engine OFF, verify that DTC U0100-U0299 is not set with symptom byte 00.
瀚慖f the DTC U0100-U0299 is set with symptom byte 00, refer to Circuit/System Testing.
5. Verify that DTC U0100-U0299 is not set with symptom byte 71 or 72.
瀚慖f the DTC U0100-U0299 is set with symptom byte 71 or 72 along with other DTCs set, diagnose all other codes first. Refer to
Diagnostic Trouble Code (DTC) List - Vehicle (See: Diagnostic Trouble Code Descriptions/Diagnostic Trouble Code (DTC) List -
Vehicle).
瀚慖f the DTC U0100-U0299 is set with symptom byte 71 or 72 and without other DTCs set, reprogram the control module. If the DTC
resets, replace the control module.
Circuit/System Testing
Note: Use the schematic to identify the following:
* Control modules the vehicle is equipped with
* Control module locations on the low and high speed GMLAN serial data circuits
* The control modules B+, ignition, ground, communication enable and serial data circuit terminals
1. Ignition OFF, disconnect the harness connector at of the control module that is not communicating.
2. Test for less than 10 ohm between each ground circuit terminal and ground.
瀚慖f greater than the specified range, test the ground circuit for an open/high resistance.
3. If equipped, verify that a test lamp illuminates between each B+ circuit terminal and ground.
瀚慖f the test lamp does not illuminate, test the B+ circuit for a short to ground or an open/high resistance. If the circuit fuse is open, test the
control circuits of the control module for a short to ground. If the circuits test normal, replace the control module.
4. If equipped, ignition ON, verify that a test lamp illuminates between each ignition circuit terminal and ground.
瀚慖f the test lamp does not illuminate, test the ignition circuit for a short to ground or an open/high resistance. If the circuit fuse is open, test
the control circuits of the control module for a short to ground. If the circuits test normal, replace the control module.
Note: Only the high speed GMLAN modules have a serial data communication enable circuit OR an accessory wake up serial data circuit,
and the BCM is the output for these circuits. Refer to the control module schematics to identify which modules have these circuits.
5. If equipped, ignition ON, verify that a test lamp illuminates between the communication enable circuit terminal OR the accessory wake up
circuit terminal and ground.
瀚慖f the test lamp does not illuminate, test the entire circuit, including the B+ circuit to the BCM, for an open/high resistance or short to
ground. If the circuits test normal, replace the BCM.
6. Ignition OFF for 60 seconds, test for less than 5 ohm between the serial data circuit terminals and the appropriate DLC terminal listed below:
* Class 2 serial data circuit terminal 2
* Low speed GMLAN serial data terminal 1
* High speed GMLAN serial data terminal 6 or 14
瀚慖f greater than the specified range, test the serial data circuit for an open/high resistance between the non communicating control module
and a module setting the DTC or a serial data splice pack.
7. If all circuits test normal, replace the control module that is not communicating.
