Envoy 2WD L6-4.2L (2008)
diagnostic purposes. DTCs may be set due to this symptom and during this diagnostic procedure. Complete the diagnostic procedure in order to ensure
all the DTCs are diagnosed and cleared from memory.
Diagnostic Aids
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The body control module (BCM) detects that the ignition is ON and sends the appropriate power mode message to the other modules. Therefore,
the BCM must be connected to the DLC for any other module to communicate with the scan tool.
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This test is used for a total class 2 serial data communication failure. If only 1 module is not communicating and sets no DTC, ensure that the
vehicle is equipped with the module, then use DTC U1001-U1254 for diagnostics.
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The following conditions may cause a total loss of class 2 serial data communication:
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The class 2 serial data circuit shorted to ground or voltage.
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A module internal malfunction that causes a short to voltage or ground on the class 2 serial data circuit.
Circuit/System Testing
Class 2 Communication Initial Test
1. Test for less than 1 ohm between the DLC ground circuit terminal 5 and ground.
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If greater than the specified range, test the ground circuit for open/high resistance.
2. Ignition OFF, disconnect the harness connector of JX305 and attempt to communicate with the BCM. Communication should not be available.
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If communication is available, refer to JX305 Test.
3. Ignition OFF, disconnect the harness connector of JX205.
4. Ignition ON, test for less than 1 volt between the serial data circuit terminal H of JX205 and ground.
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If greater than the specified range, test the serial data circuit for a short to voltage.
5. Test for infinite resistance between the serial data circuit terminal H of JX205 and ground.
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If less than the specified value, test the serial data circuit for a short to ground.
6. Ignition ON, test for less than 1 volt between the serial data circuit terminal A of JX205 and ground.
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If greater than the specified range, test the serial data circuit for a short to voltage.
7. Test for infinite resistance between the serial data circuit terminal A of JX205 and ground.
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If less than the specified value, test the serial data circuit for a short to ground.
8. Test for less than 1 ohm on the serial data circuit between terminal A of JX205 and terminal 2 of the DLC.
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If greater than the specified range, test the serial data circuit for open/high resistance.
9. Ignition OFF, disconnect the harness connectors X1 and X3 of the BCM
10. Verify a test lamp illuminates between each ground circuit terminal of the BCM listed below and B+.
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X3 - A11
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X3 - B11
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If the test lamp does not illuminate, test the ground circuit for an open/high resistance.
11. Ignition ON, verify a test lamp illuminates between each voltage circuit terminal of the BCM listed below and ground.
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X1 - A3
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X1 - A19
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X3 - A1
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X3 - A2
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X3 - A20
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X3 - B4
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X3 - B13
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X3 - B15
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X3 - B17
