Envoy 4WD V8-5.3L VIN P (2004)
Step 29
The numbers below refer to the step numbers on the diagnostic table.
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:
3. The following DTCs may be retrieved with a history status, but are not the cause of the present condition.
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U1300
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U1301
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U1305
6. A state of health DTC with a history status may be present along with a U1000 code having a current status. This indicates that the malfunction
occurred when the ignition was ON.
7. Data link connector terminals 2 and 5 provide the connection to the class 2 serial data circuit and the signal ground circuit respectively.
10. A poor connection at DLC terminal of the splice pack SP205 would cause this condition but will not set a DTC.
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.
This condition will not set a DTC.
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.
13. This test isolates the BCM class 2 serial data circuits.
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.
21. This test isolates the rest of the splice pack SP205 serial data circuits.
25. If there are no current DTCs that begin with a "U", the communication malfunction has been repaired.
26. The communication malfunction may have prevented diagnosis of the customer complaint.
Scan Tool Does Not Power Up
SCAN TOOL DOES NOT POWER UP
CIRCUIT DESCRIPTION
The data link connector (DLC) is a standardized 16 cavity connector. Connector design and location is dictated by an industry wide standard, and is
required to provide the following:
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Scan tool power battery positive voltage at terminal 16
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Scan tool power ground at terminal 4
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Common signal ground at terminal 5
The scan tool will power up with the ignition OFF. Some modules however, will not communicate unless the ignition is ON and the power mode
master (PMM) module sends the appropriate power mode message.
TEST DESCRIPTION