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Tahoe / Yukon Service Manual

DTC B1A1B (A11 Radio)

Diagnostic Instructions Perform the Diagnostic System Check prior to using this diagnostic procedure: Diagnostic System Check - Vehicle Review the description of Strategy Based Diagnosis: Strategy Based Diagnosis An overview of each diagnostic category can be found here: Diagnostic Procedure Instructions DTC Descriptor Ethernet Bus 2 (+) DTC B1A1B For symptom byte information, refer to Symptom Byte List. Diagnostic Fault Information

Circuit Short to Ground Open/High Resistance Short to Voltage Signal Performance
B+ B1A1B B1A1B — —
Ignition B1A1B B1A1B — —
Ethernet Bus 2 [+] (circuit 4758) B1A1B B1A1B B1A1B —
Ethernet Bus 2 [-] (circuit 4757) B1A1B B1A1B B1A1B —
Ground — B1A1B — —

Circuit/System Description The Ethernet bus 2 is used to communicate between K56 Serial Data Gateway Module and A11 Radio. This Ethernet harness consists of a single twisted copper pair of wires (circuits 4757 & 4758) from point to point. Conditions for Running the DTC The system voltage is between 9–16 V. Conditions for Setting the DTC A supervised periodic message that includes the transmitter device availability has not been received. Action Taken When the DTC Sets The device is never signaled. Therefore, the specific subsystems will not function. Conditions for Clearing the DTC A current DTC will clear when the diagnostic runs and passes. A history DTC will clear after 100 consecutive malfunction-free ignition cycles. Reference Information Schematic Reference Data Communication Schematics Control Module References Connector End View Reference Master Electrical Component List Description and Operation Data Link Communications Description and Operation Electrical Information Reference Circuit Testing Connector Repairs Testing for Intermittent Conditions and Poor Connections Wiring Repairs Scan Tool Reference Control Module References for scan tool information Circuit/System Verification

  1. Ignition ON/Vehicle In Service Mode.
  2. Verify that DTC U0073–U007E, DTC U0100–U02FF, or DTC U1600–U17FF is not set. ⇒ If any of the DTCs are set Refer to Diagnostic Trouble Code (DTC) List - Vehicle. ⇓ If none of the DTCs are set
  3. Refer to Circuit/System Testing. Circuit/System Testing
  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. ⇓ 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 4.1. Test for an open/high resistance in the B+ circuit. ⇒ If an open/high resistance is found, repair the fault on the circuit. ⇓ If an open/high resistance is not found 4.2. 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 4.1. Test for a short to ground in the B+ circuit. ⇒ If a short to ground is found, repair the fault in the circuit. ⇓ If a short to ground is not found 4.2. Replace the K56 Serial Data Gateway Module. ⇓ 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 5.1. Test for an open/high resistance in the ignition circuit. ⇒ If an open/high resistance is found, repair the fault in the circuit. ⇓ If an open/high resistance is not found 5.2. 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 5.1. Test for a short to ground in the ignition circuit. ⇒ If a short to ground is found, repair the fault in the circuit. ⇓ If a short to ground is not found 5.2. Replace the K56 Serial Data Gateway Module. ⇓ If the test lamp illuminates
  6. Ignition/Vehicle OFF, disconnect the harness connectors at the A11 Radio.
  7. Ignition ON/Vehicle In Service Mode.
  8. Test for less than 4.5 V between each of the Ethernet bus 2 circuit terminals and ground. ⇒ If 4.5 V or greater Repair the short to voltage in the circuit. ⇓ If less than 4.5 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 2 circuit terminals and ground. ⇒ If less than infinite resistance Repair the short to ground in the circuit. ⇓ If infinite resistance
  11. Test for infinite resistance between the pair of the Ethernet bus 2 circuit terminals. ⇒ If less than infinite resistance Repair the short together in the circuits. ⇓ If infinite resistance
  12. Test for less than 2 Ω in each of the Ethernet bus 2 circuits end to end. ⇒ If 2 Ω or greater Repair the open/high resistance in the circuit. ⇓ If less than 2 Ω
  13. Replace the K56 Serial Data Gateway Module.
  14. 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.
  15. Ignition ON/Vehicle In Service Mode.
  16. Verify DTC B1A1B does not set. ⇒ If the DTC sets Replace the A11 Radio. ⇓ If the DTC does not set
  17. All OK. Repair Instructions Perform the Diagnostic Repair Verification after completing the repair: Diagnostic Repair Verification. For control module replacement, programming, and setup, refer to: Control Module References.