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Tahoe / Yukon Service Manual

DTC U3003

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 Description DTC U3003 16 Battery Voltage Circuit Voltage Below Threshold DTC U3003 17 Battery Voltage Circuit Voltage Above Threshold For symptom byte information, refer to Symptom Byte List. Circuit/System Description The Control Module monitors the voltage in the battery positive voltage circuit. If the monitored voltage is improper, the control module will set DTC U3003. Conditions for Running the DTC Ignition “ON”. Conditions for Setting the DTC Improper battery voltage detected by the control module. Actions Taken when the DTC Sets The control module immediately disables all outputs, except the serial data. Other DTC settings are inhibited. Conditions for Clearing the DTC The conditions for setting the DTC are no longer present. Diagnostic Aids A high or low voltage DTC set or voltage value in multiple modules/sensors indicates a concern in the charging system. A possible cause of this DTC could be overcharging with a battery charger or jump starting. Reference Information Schematic Reference Starting and Charging Schematics Power Distribution Schematics Connector End View Reference Master Electrical Component List Description and Operation Charging 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 Refer to Control Module References for scan tool information Circuit/System Verification

  1. Ignition “OFF”, measure and record the battery voltage at the battery terminals.
  2. Verify the battery voltage stabilizes between 12.4 V and 12.8 V within a few minutes of ignition “OFF”. ⇒ If battery voltage is less than 12.4 V or more than 12.8 V refer to Battery Inspection/Test. ⇓ If battery voltage is between 12.4 V and 12.8 V
  3. Vehicle in Propulsion Mode, headlights ON, measure and record the battery voltage at the battery terminals.
  4. Verify the voltage is at least 1 V greater than the voltage measured in step 1, but less than 15 V. ⇒ If the voltage is not at least 1 V greater than the voltage measured in step 1 or is greater than 15 V Refer to Charging System Test. ⇓ If the voltage is at least 1 V greater than the voltage measured in step 1, but less than 15 V
  5. Verify the appropriate control module battery voltage and ignition voltage parameters are available in the scan tool. ⇒ If parameters are not available in the scan tool Refer to “Circuit/System Testing”. ⇓ If parameters are available in the scan tool
  6. Verify the appropriate control module scan tool battery voltage and ignition voltage parameters are within 1 V of the battery voltage. ⇒ If not within 1 V of the battery voltage Refer to “Circuit/System Testing”. ⇓ If within 1 V of the battery voltage
  7. The condition may be an intermittent fault and is not currently present. Circuit/System Testing
  8. Ignition “OFF” and all vehicle systems OFF, disconnect the harness connectors at the appropriate control module that is setting the DTC. It may take up to 2 min for all vehicle systems to power down.
  9. Test for less than 10 Ω between each ground circuit terminal and ground. ⇒ If 10 Ω or greater 2.1. ignition “OFF”. 2.2. Test for less than 2 Ω in the ground circuit end to end. ⇒ If the measured resistance is 2 Ω or greater, repair the open/high resistance in the circuit. ⇒ If less than 2 Ω, repair the open/high resistance in the ground connection. ⇓ If less than 10 Ω
  10. Vverify a test lamp illuminates between each B+ circuit terminal and ground. ⇒ If the test lamp does not illuminate and the circuit fuse is good 3.1. ignition “OFF”. 3.2. Test for less than 2 Ω in the B+ circuit end to end. ⇒ If the measured resistance is 2 Ω or greater, repair the open/high resistance in the circuit. ⇒ If less than 2 Ω, 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 3.1. ignition “OFF”. 3.2. Test for infinite resistance between the B+ circuit and ground. ⇒ If the measured resistance is not infinite, repair the short to ground in the circuit. ⇒ If the measured resistance is infinity, replace the corresponding control module. ⇓ If the test lamp is ON
  1. Ignition “ON”.
  2. If equipped, verify a test lamp illuminates between each ignition circuit terminal and ground. ⇒ If the test lamp does not illuminate and the circuit fuse is good 5.1. Ignition “OFF”. 5.2. Test for less than 2 Ω in the ignition circuit end to end. ⇒ If the measured resistance is 2 Ω or greater, repair the open/high resistance in the circuit. ⇒ If less than 2 Ω, 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. Ignition “OFF”. 5.2. Test for infinite resistance between the ignition circuit and ground. ⇒ If the measured resistance is not infinite, repair the short to ground in the circuit. ⇒ If the measured resistance is infinity, replace the corresponding control module. ⇓ If the test lamp is ON
  3. Replace the appropriate control module. Repair Instructions Perform the Diagnostic Repair Verification after completing the repair. Refer to Control Module References for control module replacement, programming, and setup.