Test Description

WARNING: This page does not describe the selected car, but rather 6 other vehicles, including the 2005 Isuzu Ascender, 2005 GMC Envoy XUV, 2005 GMC Envoy XL, 2005 GMC Envoy, and 2005 Chevrolet TrailBlazer. However, it is still accessible from the selected car via links, so may be relevant.

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

6: 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 splice pack SP306 serial data circuits.
14: This test isolates the splice pack SP205 serial data circuits.
20: If there are no current DTCs that begin with a "U", the communication malfunction has been repaired.
21: The communication malfunction may have prevented diagnosis of the customer complaint.

DTC U1300, U1301, or U1305 (5.3L)

Step	Action	Yes	No
Schematic Reference: Data Link Connector (DLC) Schematics Connector End View Reference: Master Electrical Component List in Wiring Systems
1	Did you perform the Diagnostic System Check - Vehicle?	Go to Step 2	Go to Diagnostic System Check - Vehicle in Vehicle DTC Information
2	Did you record U1300 or U1301, as current?	Go to Step 4	Go to Step 3
3	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 2 serial data circuit for an intermittent short to ground or an intermittent short to voltage. Refer to the following in Wiring Systems: Testing for Intermittent Conditions and Poor Connections Circuit Testing Connector Repairs Wiring Repairs Did you find and correct the condition?	Go to Step 22	-
4	Turn OFF the ignition. Disconnect the engine control module (ECM). Turn ON the ignition. Attempt to communicate with the body control module (BCM). Does the scan tool communicate with BCM?	Go to Step 18	Go to Step 5
5	Turn OFF the ignition. Reconnect the ECM. Disconnect the splice pack SP306. Turn ON the ignition, with the engine OFF. Retrieve the DTCs from the ECM. Did you record U1300 or U1301, as current?	Go to Step 8	Go to Step 6
6	Repeat the following steps on the class 2 serial data circuits connected to the splice pack SP306 until the concern is located: Turn OFF the ignition. Using the correct terminal adapter, connect a jumper wire to the splice pack SP205 terminal of the splice pack SP306. Connect the other end of the jumper wire, using correct terminal adapter, to the terminal for the devices connected to splice pack SP306. Turn ON the ignition, with the engine OFF. Retrieve the DTCs from the ECM. Did you record U1300 or U1301, as current?	Go to Step 7	Go to Testing for Intermittent Conditions and Poor Connections in Wiring Systems
7	Turn OFF the ignition. Disconnect the module that caused the DTC to be set. Test the class 2 serial data circuit between the splice pack SP306 and the respective 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 20	Go to Step 18
8	Turn OFF the ignition. Disconnect the splice pack SP205. Turn ON the ignition, with the engine OFF. Retrieve DTCs from ECM. Did you record U1300 or U1301, as current?	Go to Step 9	Go to Step 12
9	Turn OFF the ignition. Disconnect the theft deterrent control module (VTD), if equipped, or disconnect the BCM, if not equipped with VTD. Turn ON the ignition, with the engine OFF. Retrieve DTCs from ECM. Did you record U1300 or U1301, as current?	Go to Step 11	Go to Step 10
10	Turn OFF the ignition. Test the class 2 serial data circuit between VTD, if equipped, or BCM if not equipped with VTD, and splice pack SP205 for a short to ground or a short to voltage. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition?	Go to Step 20	Go to Step 16
11	Turn OFF the ignition. Disconnect the ECM. Test the class 2 serial data circuit between the ECM and VTD, if equipped, or BCM if not equipped with VTD, 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. Test the class 2 serial data circuit between the ECM and splice pack SP306 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 20	Go to Step 16
12	Turn OFF the ignition. Using the correct terminal adapter, connect a jumper wire to the ECM terminal of the splice pack SP205. Connect the other end of the jumper wire, using correct terminal adapter, to the splice pack SP306 terminal of the splice pack SP205. Turn ON the ignition, with the engine OFF. Retrieve DTCs from ECM. Did you record U1300 or U1301, as current?	Go to Step 13	Go to Step 14
13	Turn OFF the ignition. Repair the short to ground or short to voltage in the class 2 serial data circuit between the splice pack SP205 and the splice pack SP306. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition?	Go to Step 20	-
14	Repeat the following steps on the class 2 serial data circuits connected to the splice pack SP205 until the concern is located: Turn OFF the ignition. Leave the jumper wire connected to the ECM terminal of the splice pack SP205. Connect the other end of the jumper wire, using correct terminal adapter, to the terminal for the devices connected to splice pack SP205. Turn ON the ignition, with the engine OFF. Retrieve DTCs from ECM. Did you record U1300 or U1301, as current?	Go to Step 15	Go to Testing for Intermittent Conditions and Poor Connections in Wiring Systems
15	Turn OFF the ignition. Disconnect the module that caused the DTC to be set. Test the class 2 serial data circuit between the splice pack SP205 and the respective 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 20	Go to Step 18
16	Inspect for poor connections at the class 2 serial data circuit of the VTD, if equipped, or BCM, if not equipped with VTD. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition?	Go to Step 20	Go to Step 17
17	Replace the VTD, if equipped, or BCM, if not equipped with VTD. Refer to Control Module References for replacement, setup, and programming. Did you complete the replacement?	Go to Step 20	-
18	Inspect for poor connections at the class 2 serial data circuit of the last disconnected module. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition?	Go to Step 20	Go to Step 19
19	Replace the last disconnected module. Refer to Control Module References for replacement, setup, and programming. Did you complete the replacement?	Go to Step 20	-
20	Reconnect all of the disconnected modules and splice packs. Install a scan tool. Turn ON the ignition, with the engine OFF. Retrieve the DTCs. Did you record any DTCs which begin with a "U" and with a current status?	Go to Diagnostic Trouble Code (DTC) List - Vehicle in Vehicle DTC Information	Go to Step 21
21	Did you record any DTCs which do not begin with a "U"?	Go to Diagnostic Trouble Code (DTC) List - Vehicle in Vehicle DTC Information	Go to Step 22
22	Use the scan tool in order to clear the DTCs. Did you complete the action?	System OK	-