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Test Description

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.
  2. 3:  DTCs U1300, U1301, or U1305 may be retrieved with a history status. These DTCs are not the cause of the present condition.
  3. 6:  A state of health DTC with a history status may be present along with a U1000 having a current status. This indicates the malfunction occurred when the ignition was ON.
  4. 7:  Data link connector terminals 2 and 5 provide the connection to the class 2 serial data circuit and the signal ground circuit respectively.
  5. 9:  A poor connection at the DLC terminal would cause this condition but will not set a DTC.
  6. 10:  An open in the class 2 serial data circuit between the DLC and the star connector will prevent the scan tool from communicating with any module. This condition will not set a DTC.
  7. 11:  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 wiring for a short, make sure there is not a module connected to the wire being tested. This test isolates the powertrain control module (PCM) class 2 serial data circuit.
  8. 13:  This test isolates the inflatable restraint sensing and diagnostic module (SDM) class 2 serial data circuit.
  9. 15:  This test isolates the electronic brake control module (EBCM) class 2 serial data circuit.
  10. 17:  This test isolates the instrument panel cluster (IPC) class 2 serial data circuit.
  11. 19:  This test isolates the theft deterrent control module class 2 serial data circuit.
  12. 21:  This test isolates the driver information center (DIC) class 2 serial data circuit.
  13. 23:  This test isolates the radio class 2 serial data circuit.
  14. 33:  If there are no current DTCs that begin with a U, the communication malfunction has been repaired.
  15. 35:  The communication malfunction may have prevented diagnosis of the customer complaint.
Scan Tool Does Not Communicate with Class 2 Device

Step Action Yes No
Schematic Reference: Data Link Connector (DLC) Schematics 
Connector End View Reference: Computer/Integrating Systems Connector End Views  or Master Electrical Component List in Wiring Systems
1 Does the scan tool power up? Go to Step 2  Go to Scan Tool Does Not Power Up 
2 
  1. Turn ON the ignition, with the engine OFF.
  2. Attempt to communicate with each module on the class 2 serial data circuit. If using a Tech 2, obtain this information using the Class 2 Message Monitor feature.
Does the scan tool communicate with any module on the class 2 serial data circuit?		 Go to Step 3  Go to Step 7 
3 
  1. Select the display DTCs function for each module. If using a Tech 2, use the Class 2 DTC Check feature in order to determine which modules do have DTCs set.
  2. Record all of the displayed DTCs, the DTC status, and the module which set the DTC.
Did you record any DTCs in the range of U1000-U1305?		 Go to Step 4  Go to Diagnostic Aids
4 Are history DTCs U1300, U1301, or U1305 retrieved from any module? Go to Step 5  Go to Step 6 
5
IMPORTANT: Turn ON the ignition, with the engine OFF, when testing for a short to voltage. Use the DMM MIN/MAX function to capture intermittent conditions.
Test the class serial data circuit for an intermittent short to ground or an intermittent short to voltage. Refer to the following in Wiring Systems:Did you find and correct the condition?		 Go to Step 33  Go to Step 6 
6  Is U1000 or U1255 the only DTC displayed in the previously specified range? Go to DTC U1000 and U1255  Go to DTC U1001-U1254 
7 
  1. Turn OFF the ignition.
  2. Disconnect the scan tool from the data link connector (DLC).
  3. Inspect for poor connections/terminal tension at the DLC terminals 2 and 5. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems.
Did you find and correct the condition?		 Go to Control Module References  Go to Step 8 
8 Test the DLC ground circuit terminal 5 for an open. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.
Did you find and correct the condition?		 Go to Control Module References  Go to Step 9 
9 
  1. Disconnect the star connector.
  2. Inspect for poor connections/terminal tension at the star connector. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems.
Did you find and correct the condition?		 Go to Control Module References  Go to Step 10 
10  Test the class 2 serial data circuit for an open, a short to ground, or a short to B+ between the DLC terminal 2 and the star connector terminal A. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.
Did you find and correct the condition?		 Go to Control Module References  Go to Step 11 
11 
  1. Connect a jumper wire to the DLC terminal of the star connector.
  2. Connect the other end of the jumper wire to the powertrain control module (PCM) terminal of the star connector.
  3. Turn ON the ignition, with the engine OFF.
  4. Attempt to communicate with the PCM.
Does the scan tool communicate with the PCM?		 Go to Step 13  Go to Step 12 
12
  1. Turn OFF the ignition.
  2. Disconnect the PCM.
  3. Test the class 2 serial data circuit between the star connector and the PCM for a short to ground or a short to voltage. Turn ON the ignition, with the engine OFF, when testing for a short to voltage. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.
Did you find and correct the condition?		 Go to Step 33  Go to Step 31 
13 
  1. Disconnect the jumper wire from the PCM terminal of the star connector.
  2. Connect the jumper wire to the inflatable restraint sensing and diagnostic module (SDM) terminal of the star connector.
  3. Turn ON the ignition, with the engine OFF.
  4. Attempt to communicate with the SDM.
Does the scan tool communicate with the SDM?		 Go to Step 15  Go to Step 14 
14
  1. Turn OFF the ignition.
  2. Disconnect the SDM.
  3. Test the class 2 serial data circuit between the star connector and the SDM for a short to ground or a short to voltage. Turn ON the ignition, with the engine OFF, when testing for a short to voltage. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.
Did you find and correct the condition?		 Go to Step 33  Go to Step 31 
15 
  1. Disconnect the jumper wire from the SDM terminal of the star connector.
  2. Connect the jumper wire to the electronic brake control module (EBCM) terminal of the star connector.
  3. Turn ON the ignition, with the engine OFF.
  4. Attempt to communicate with the EBCM.
Does the scan tool communicate with the EBCM?		 Go to Step 17  Go to Step 16 
16
  1. Turn OFF the ignition.
  2. Disconnect the EBCM.
  3. Test the class 2 serial data circuit between the star connector and the EBCM for a short to ground or a short to voltage. Turn ON the ignition, with the engine OFF, when testing for a short to voltage. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.
Did you find and correct the condition?		 Go to Step 33  Go to Step 31 
17 
  1. Disconnect the jumper wire from the EBCM terminal of the star connector.
  2. Connect the jumper wire to the instrument panel cluster (IPC) terminal of the star connector.
  3. Turn ON the ignition, with the engine OFF.
  4. Attempt to communicate with the IPC.
Does the scan tool communicate with the IPC?		 Go to Step 19  Go to Step 18 
18
  1. Turn the ignition OFF.
  2. Disconnect the IPC.
  3. Test the class 2 serial data circuit between the star connector and the IPC for a short to ground or a short to voltage. Turn ON the ignition, with the engine OFF, when testing for a short to voltage. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.
Did you find and correct the condition?		 Go to Step 33  Go to Step 31 
19 
  1. Disconnect the jumper wire from the IPC terminal of the star connector.
  2. Connect the jumper wire to the theft deterrent control module terminal of the star connector.
  3. Turn ON the ignition, with the engine OFF.
  4. Attempt to communicate with the theft deterrent control module.
Does the scan tool communicate with the theft deterrent control module?		 Go to Step 21  Go to Step 20 
20
  1. Turn OFF the ignition.
  2. Disconnect the theft deterrent control module.
  3. Test the class 2 serial data circuit between the star connector and the theft deterrent control module for a short to ground or a short to voltage. Turn ON the ignition, with the engine OFF, when testing for a short to voltage. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.
Did you find and correct the condition?		 Go to Step 33  Go to Step 31 
21 
  1. Disconnect the jumper wire from the theft deterrent control module terminal of the star connector.
  2. Connect the jumper wire to the driver information center (DIC) terminal of the star connector.
  3. Turn ON the ignition, with the engine OFF.
  4. Attempt to communicate with the DIC.
Does the scan tool communicate with the DIC?		 Go to Step 23  Go to Step 22 
22
  1. Turn OFF the ignition.
  2. Disconnect the DIC.
  3. Test the class 2 serial data circuit between the star connector and the DIC for a short to ground or a short to voltage. Turn ON the ignition, with the engine OFF, when testing for a short to voltage. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.
Did you find and correct the condition?		 Go to Step 33  Go to Step 31 
23 
  1. Disconnect the jumper wire from the DIC terminal of the star connector.
  2. Connect the jumper wire to the radio terminal of the star connector.
  3. Turn ON the ignition, with the engine OFF.
  4. Attempt to communicate with the radio.
Does the scan tool communicate with the radio?		 Go to Step 33  Go to Step 24 
24
  1. Turn OFF the ignition.
  2. Disconnect the class 2 serial data circuit from rear video/audio/HVAC.
  3. Turn ON the ignition, with the engine OFF.
  4. Attempt to communicate with the radio.
Does the scan tool communicate with the radio?		 Go to Step 32  Go to Step 25 
25
  1. Turn OFF the ignition.
  2. Disconnect the rear video/audio/HVAC class 2 serial data circuit at the video disc player.
  3. Turn ON the ignition, with the engine OFF.
  4. Attempt to communicate with the radio.
Does the scan tool communicate with the radio?		 Go to Step 26  Go to Step 27 
26
  1. Turn OFF the ignition.
  2. Disconnect the rear video/audio/HVAC and video disc player.
  3. Test the class 2 serial data circuit between the rear video/audio/HVAC and video disc player for a short to ground or a short to voltage. Turn ON the ignition, with the engine OFF, when testing for a short to voltage. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.
Did you find and correct the condition?		 Go to Step 33  Go to Step 31 
27
  1. Turn OFF the ignition.
  2. Disconnect the class 2 serial data circuit from video disc player.
  3. Turn ON ignition, with the engine OFF.
  4. Attempt to communicate with the radio.
Does the scan tool communicate with the radio?		 Go to Step 32  Go to Step 28 
28
  1. Turn OFF the ignition.
  2. Disconnect the video disc player class 2 serial data circuit at the radio.
  3. Turn ON the ignition, with the engine OFF.
  4. Attempt to communicate with the radio.
Does the scan tool communicate with the radio?		 Go to Step 29  Go to Step 30 
29
  1. Turn OFF the ignition.
  2. Disconnect the video disc player and the radio.
  3. Test the class 2 serial data circuit between the video disc player and the radio for a short to ground or a short to voltage. Turn ON the ignition, with the engine OFF, when testing for a short to voltage. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.
Did you find and correct the condition?		 Go to Step 33  Go to Step 31 
30
  1. Turn OFF the ignition.
  2. Disconnect the radio.
  3. Test the class 2 serial data circuit between the star connector and the radio for a short to ground or a short to voltage. Turn ON the ignition, with the engine OFF, when testing for a short to voltage. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.
Did you find and correct the condition?		 Go to Step 33  Go to Step 31 
31 Inspect for poor connections/terminal tension at the class 2 serial data circuit of the module that is not communicating. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems.
Did you find and correct the condition?		 Go to Step 33  Go to Step 32 
32 Replace the module which is not communicating. Refer to Control Module References  for replacement, setup, and programming.
Did you complete the replacement?		 Go to Step 33  -
33 
  1. Reconnect all of the disconnected modules.
  2. Reconnect any other disconnected connectors.
  3. Install a scan tool.
  4. Turn ON the ignition, with the engine OFF.
  5. Wait for 10 seconds. The scan tool may require a power up reset before communication will occur due to a short on the class 2 serial data circuit. Turn OFF or disconnect the scan tool prior to performing this test.
  6. Select the display DTCs function for each module. If using a Tech 2, use the Class 2 DTC Check feature in order to determine which modules do have DTCs set.
  7. Record all of the displayed DTCs and the DTC status.
Did you record any DTCs which begin with a U and with a current status?		 Go to Step 35  Go to Step 34 
34 Did you record any DTCs which do not begin with a U? Go to Step 35  Go to Step 37 
35  Diagnose the DTCs as directed by the diagnostic procedures for the particular module or malfunction.
Did you complete the action?		 Go to Step 36  -
36 Did you diagnose all of the DTCs? Go to Step 37  Go to Step 35 
37 Clear the DTCs using the scan tool.
Did you complete the action?		 System OK -
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