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Tahoe / Yukon Service Manual

DTC P305D or P305E

Diagnostic Instructions Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure. Review Strategy Based Diagnosis for an overview of the diagnostic approach. Diagnostic Procedure Instructions provides an overview of each diagnostic category. DTC Descriptors DTC P305D DC/DC Converter Crank Input Signal Circuit High DTC P305E DC/DC Converter Crank Input Signal Circuit Low For symptom byte information, refer to Symptom Byte List Diagnostic Fault Information

Circuit Number Circuit Function Short to Ground Open/High Resistance Short to Voltage Signal Performan
8040 B+ 1 1 — —
8140 B+ 1 1 — —
625 Control P305E, 1 P305E, 1 P305D, 2 —
4054 Serial Data P305D, P305E P305D, P305E P305D, P305E —
4055 Serial Data P305D, P305E P305D, P305E P305D, P305E —
4320 Serial Data U18A7, U18E2, P305D, P305E U18A7, U18E2, P305D, P305E P16D9, P305D, P305E —
250 Ground — P305D, P305E, 1 — —
1. Starter Solenoid Does Not Click 2. Starter spins all the time

Circuit/System Description The T19 Power Supply Transformer is supplied voltage through B+ circuit 8040 and B+ circuit  8140. Ground is provided by ground circuit 250, of which there are two redundant circuits. The T19 Power Supply Transformer is used to maintain constant battery voltage to necessary components during an auto engine stop/start event. At the T19 Power Supply Transformer, the B+ circuit 8040 provides voltage to control circuit 2172 and B+ circuit 8140 provides voltage to control circuit 2173. The K20 Engine Control Module commands the KR27 Starter Relay by providing voltage on the control circuit 625. The T19 Power Supply Transformer monitors control circuit 625 as an indicator that the K20 Engine Control Module has commanded the engine to start, ending the auto engine stop/start event. During the engine start, the T19 Power Supply Transformer will supply voltage on control circuit 2173, which provides critical components and control module a stable voltage during the engine start event. The T19 Power Supply Transformer communicates voltage on control circuit 2172 and control circuit 2173 to the K20 Engine Control Module on the powertrain CAN bus. The K20 Engine Control Module compares voltage on ignition circuit 439 voltage to the indicated voltage received from the T19 Multifunction Power Supply Converter to determine if there is a system fault. Conditions for Running the DTC Ignition ON Conditions for Setting the DTC P305D The K20 Engine Control Module detects the T19 Power Supply Transformer crank control is high when it should be low. P305E The K20 Engine Control Module the T19 Power Supply Transformer crank control is low when it should be high. Action Taken When the DTC Sets DTC P305D is a type B DTC. DTC P305E is a type A DTC. Conditions for Clearing the DTC DTC P305D is a type B DTC. DTC P305E is a type A DTC. Diagnostic Aids These DTC’s can be set when programming the K20 Engine Control Module. Please follow the programming and setup instructions if a DTC sets. Reference Information Schematic Reference Starting and Charging Schematics Connector End View Reference Master Electrical Component List Description and Operation Stop/Start System Description and Operation Electrical Information Reference Circuit Testing Connector Repairs Testing for Intermittent Conditions and Poor Connections Wiring Repairs DTC Type Reference Powertrain Diagnostic Trouble Code (DTC) Type Definitions Scan Tool Reference Control Module References for scan tool information Circuit/System Verification

  1. Ignition ON.
  1. Verify there are no system voltage DTCs set as current or history in any control module. ⇒ If any system voltage DTCs are set Diagnose these DTCs first. Refer to Diagnostic Trouble Code (DTC) List - Vehicle. ⇓ If no system voltage DTCs are set
  2. Ignition Off and all vehicle systems OFF.
  1. Verify the battery voltage is within 12.4 V to 12.8 V at the C1 Battery. ⇒ If not within the specified range Refer to Battery Inspection/Test ⇓ If within the specified range
  2. Engine Running with all accessories off, allow the system voltage to stabilize.
  3. Test for 13 V to 15 V at the C1 Battery. ⇒ If not within the specified value Refer to Charging System Test ⇓ If within the specified range
  4. Verify DTC U18A7, U18E2, P0615, P0616, P0617, P16D7, P16D8, or P16D9 are set as current. ⇒ If any of the U18A7, U18E2, P0615, P0616, P0617, P16D7, P16D8, or P16D9 are set as current Diagnose these DTCs first. Refer to Diagnostic Trouble Code (DTC) List - Vehicle. ⇓ If DTC U18A7, U18E2, P0615, P0616, P0617, P16D7, P16D8, or P16D9 are not set as current
  5. Refer to Circuit/System Testing. Circuit/System Testing
  6. Ignition/vehicle OFF, disconnect the connector at the T19 Power Supply Transformer.
  7. Verify a test lamp illuminates between ground circuit terminal 7 and B+. ⇒ If the test lamp does not illuminate Repair the open/high resistance on circuit 250 or the ground connection. ⇓ If the test lamp illuminates
  8. Verify a test lamp illuminates between ground circuit terminal 12 and B+. ⇒ If the test lamp does not illuminate Repair the open/high resistance on circuit 250 or the ground connection. ⇓ If the test lamp illuminates
  9. Disconnect the KR27 Starter Relay.
  10. Test for less than 2 Ω between control circuit terminal 86 and control circuit terminal 5 at the T19 Power Supply Transformer. ⇒ If 2 Ω or greater Repair the open/high resistance on circuit 625. ⇓ If less than 2 Ω
  11. Replace the T19 Power Supply Transformer Repair Instructions Perform the Diagnostic Repair Verification after completing the repair. Electrical Relay Replacement Control Module References for control module replacement, programming, and setup.