Data Link Communications System: Overview Chevrolet TrailBlazer I

Scheme 1

Scheme 2

Scheme 3

Scheme 4

Scheme 5

Scheme 6

Scheme 7

Scheme 8

Test Description

The numbers below refer to the step numbers on the diagnostic table.

1. 1. A DTC U1001 - U1254 Lost Communications with XXX with a history status may indicate the cause of U1000 or U1255.
2. 2. The modules not communicating are the likely cause of U1000 or U1255. The modules that are available on the class 2 serial data circuit are listed in the Circuit Description.
3. 6. The module which was not communicating due to a poor connection to the class 2 serial data circuit may have set DTC U1001 - U1254 Lost Communications with XXX for those modules that it was monitoring.
4. 9. The modules which can communicate indicate the module which cannot communicate. You must clear the serial data communication DTCs from these modules to avoid future misdiagnosis.
5. 12. If all modules are communicating, the module which set U1000 or U1255 may have done so due to some other condition.
6. 14. The module which set U1000 or U1255 is the likely cause of the malfunction.

Scheme 9

Scheme 10

Scheme 11

The number below refers to the step number on the diagnostic table.

1. 6. The module which was not communicating on the class 2 serial data circuit may have set Loss of Communication DTCs for those modules that it was monitoring.

Scheme 12

Scheme 13

The number below refers to the step number on the diagnostic table.

1. 4. If the battery positive voltage and ground circuits of the DLC are functioning properly. The malfunction must be due to the scan tool.

Scheme 14

The numbers below refer to the step numbers on the diagnostic table.

1. 2. A partial malfunction in the class 2 serial data circuit uses a different procedure from a total malfunction of the class 2 serial data circuit. The following modules communicate on the class 2 serial data circuit
2. 3. The following DTCs may be retrieved with a history status, but are not the cause of the present condition.

1. U1300
2. U1301
3. U1305

1. 6. A state of health DTC with a history status may be present along with a U1000 or U1255 code having a current status. This indicates that the malfunction occurred when the ignition was ON.
2. 7. Data link connector terminals 2 and 5 provide the connection to the class 2 serial data circuit and the signal ground circuit respectively.
3. 10. A poor connection at DLC terminal of the splice pack SP205 would cause this condition but will not set a DTC.
4. 11. An open in the class 2 serial data circuit between the DLC and splice pack SP205 will prevent the scan tool from communicating with any module.
5. This condition will not set a DTC.
6. 12. The class 2 serial data circuit is shorted to voltage or ground. The condition may be due to the wiring or due to a malfunction in one of the modules. When testing the wire for a short, make sure there is not a module connected to the wire being tested. This test isolates the BCM and the PCM class 2 serial data circuits.
7. 13. This test isolates the BCM class 2 serial data circuits.
8. 16. The BCM detects that the ignition is ON and sends the appropriate power mode message to the other modules. Therefore, the BCM must remain connected to the DLC for any other module to communicate with the scan tool. This test isolates the splice pack SP306 serial data circuits.
9. 21. This test isolates the rest of the splice pack SP205 serial data circuits.
10. 25. If there are no current DTCs that begin with a "U", the communication malfunction has been repaired.
11. 26. The communication malfunction may have prevented diagnosis of the customer complaint.

Scheme 15

Scheme 16

Scheme 17

Scheme 18

The numbers below refer to the step numbers on the diagnostic table.

1. 2. A partial malfunction in the class 2 serial data circuit uses a different procedure from a total malfunction of the class 2 serial data circuit. The following modules communicate on the class 2 serial data circuit
2. 3. The following DTCs may be retrieved with a history status, but are not the cause of the present condition.

1. U1300
2. U1301
3. U1305

1. 6. A state of health DTC with a history status may be present along with a U1000 or U1255 code having a current status. This indicates that the malfunction occurred when the ignition was ON.
2. 7. Data link connector terminals 2 and 5 provide the connection to the class 2 serial data circuit and the signal ground circuit respectively.
3. 10. A poor connection at DLC terminal of the splice pack SP205 would cause this condition but will not set a DTC.
4. 11. This step may eliminate the loop created by PCM and theft deterrent module from failure cause.
5. 12. An open in the class 2 serial data circuit between the DLC and splice pack SP205 will prevent the scan tool from communicating with any module.
6. This condition will not set a DTC.
7. 14. The class 2 serial data circuit is shorted to voltage or ground. The condition may be due to the wiring or due to a malfunction in one of the modules. When testing the wire for a short, make sure there is not a module connected to the wire being tested. This test isolates the BCM class 2 serial data circuits.
8. 16. This test isolates the PCM class 2 serial data circuits.
9. 18. The BCM detects that the ignition is ON and sends the appropriate power mode message to the other modules. Therefore, the BCM must remain connected to the DLC for any other module to communicate with the scan tool. This test isolates the splice pack SP306 serial data circuits.
10. 23. This test isolates the rest of the splice pack SP205 serial data circuits.
11. 27. If there are no current DTCs that begin with a "U", the communication malfunction has been repaired.
12. 28. The communication malfunction may have prevented diagnosis of the customer complaint.

Scheme 19

Scheme 20

Scheme 21

Scheme 22

Scheme 23