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HOMESERVICE MANUALSCHEVROLET2025TAHOE PPV, 4WDREPAIR AND DIAGNOSIS (SINGLE PAGE)ENGINE PERFORMANCESYSTEMDATA COMMUNICATIONS - DIAGNOSTIC INFORMATION AND PROCEDURES (1 OF 4)DIAGNOSTIC INFORMATION AND PROCEDURESDTC B1A1D (K124 IMAGE PROCESSING MODULE)CIRCUIT/SYSTEM TESTING
2025 Chevrolet Tahoe PPV, 4WD

Circuit/System Testing

2025 Chevrolet Tahoe PPV, 4WDSECTION Circuit/System Testing
NOTE:

Use the schematics and connector end views to identify the control module's ground, B+, ignition, and Ethernet serial data circuit terminals.

  1. Ignition/Vehicle OFF, disconnect the harness connectors at the K56 Serial Data Gateway Module.
  2. Verify a test lamp illuminates between each of the ground circuit terminals and B+.
    • If the test lamp does not illuminate 

      Repair the open/high resistance in the ground circuit or ground connection.

    • Go to next step: If the test lamp illuminates 
  3. Ignition ON/Vehicle In Service Mode.
  4. If equipped, verify a test lamp illuminates between each of the B+ circuit terminals and ground.
    • If the test lamp does not illuminate and the circuit fuse is good 
    1. Test for an open/high resistance in the B+ circuit.
      • If an open/high resistance is found, repair the fault on the circuit.
      • Go to next step: If an open/high resistance is not found
    2. Verify the fuse is not open and there is voltage at the fuse.
    • If the test lamp does not illuminate and the circuit fuse is open 
    1. Test for a short to ground in the B+ circuit.
      • If a short to ground is found, repair the fault in the circuit.
      • Go to next step: If a short to ground is not found
    2. Replace the K56 Serial Data Gateway Module.
    • Go to next step: If the test lamp illuminates 
  5. If equipped, verify a test lamp illuminates between each of the ignition circuit terminals, which has a fuse in the circuit, and ground.
    • If the test lamp does not illuminate and the circuit fuse is good 
    1. Test for an open/high resistance in the ignition circuit.
      • If an open/high resistance is found, repair the fault in the circuit.
      • Go to next step: If an open/high resistance is not found
    2. Verify the fuse is not open and there is voltage at the fuse.
    • If the test lamp does not illuminate and the circuit fuse is open 
    1. Test for a short to ground in the ignition circuit.
      • If a short to ground is found, repair the fault in the circuit.
      • Go to next step: If a short to ground is not found
    2. Replace the K56 Serial Data Gateway Module.
    • Go to next step: If the test lamp illuminates 
  6. Ignition/Vehicle OFF, disconnect the harness connectors at the K124 Image Processing Module.
  7. Ignition ON/Vehicle In Service Mode.
  8. Test for less than 1 V between each of the Ethernet bus 3 circuit terminals and ground.
    • If 1 V or greater 

      Repair the short to voltage in the circuit.

    • Go to next step: If less than 1 V 
  9. Ignition/Vehicle OFF, all access doors closed, all vehicle systems OFF, and all keys at least 3 m (9.8 ft) away from vehicle. It may take up to 10 min for all vehicle systems to power down.
  10. Test for infinite resistance between each of the Ethernet bus 3 circuit terminals and ground.
    • If less than infinite resistance 

      Repair the short to ground in the circuit.

    • Go to next step: If infinite resistance 
  11. Test for infinite resistance between the pair of the Ethernet bus 3 circuit terminals.
    • If less than infinite resistance 

      Repair the short together in the circuits.

    • Go to next step: If infinite resistance 
  12. Test for less than 2 Ω in each of the Ethernet bus 3 circuits end to end.
    • If 2 Ω or greater 

      Repair the open/high resistance in the circuit.

    • Go to next step: If less than 2 Ω 
  13. Inspect both harness and component connectors for contamination, corrosion, and terminal tension.
  14. Reconnect the harness connectors at the K56 Serial Data Gateway Module and the K124 Image Processing Module.
  15. Ignition ON/Vehicle In Service Mode.
  16. Verify DTC B1A1D is not set.
    • If the DTC is set 
    1. Replace the K56 Serial Data Gateway Module.
    2. Ignition ON/Vehicle In Service Mode.
    3. Verify DTC B1A1D does not set again.
      • If the DTC sets, replace the K124 Image Processing Module.
      • Go to next step: If the DTC does not set
    4. All OK.
    • Go to next step: If the DTC is not set 
  17. A fault is currently not present and may be an intermittent condition.
RENDER: 1.0x

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When to See a Mechanic

Stop DIY work and contact a certified mechanic immediately if any of the following apply:

  • • You smell fuel, burning insulation, or see smoke.
  • • Brakes feel soft, pull hard to one side, or make grinding noises.
  • • The engine overheats, stalls repeatedly, or misfires under load.
  • • You are missing required tools, torque specs, or safe lifting equipment.
  • • You are not confident in the next step or safety outcome.