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Home >> Buick >> 2018 >> Envision Base >> Repair and Diagnosis (Single Page) >> Engine Performance >> System >> Data Communication System - Diagnostic Information And Procedures >> Diagnostic Information and Procedures >> Scan Tool Does Not Communicate with Gateway Isolated Low Speed GMLAN Device >> Circuit/System Verification

Circuit/System Verification

  1. Ignition ON/Vehicle In Service Mode.
  2. Verify that DTC U0073, U0074, U0075, U0077, U0078, U007A, P06E4, P1EB9, U1814, U2099, B1325, B1330, B1370, B1380, B1424, B1428, B1440, B1441, B1517, C0800, C0899, C12E1, P0560, or P0562 is not set.
    • Go to next step: If none of the DTCs are set 
  3. Verify that the K56 Serial Data Gateway Module is communicating.
    • If the K56 Serial Data Gateway Module is not communicating 

      Refer to DTC U0100-U02FF  to diagnose the K56 Serial Data Gateway Module.

    • Go to next step: If the K56 Serial Data Gateway Module is communicating 
  4. Attempt to communicate with all devices on the gateway isolated low speed GMLAN serial data circuit. Refer to Data Link References  to determine which devices are on the gateway isolated low speed GMLAN bus.
  5. Verify which devices are communicating on the gateway isolated low speed GMLAN serial data circuit.
    • If only one device is not communicating 

      Refer to Circuit/System Testing - Testing the Device Circuits.

    • If one or more devices are communicating but not all, except the K56 Serial Data Gateway Module 

      Refer to Circuit/System Testing - Testing the Serial Data Circuit for an Open/High Resistance.

    • Go to next step: If none of the devices are communicating, except the K56 Serial Data Gateway Module 
  6. Refer to Circuit/System Testing.
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