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Tahoe / Yukon Service Manual

DTC P21CB

Engine Controls and Fuel - 3.0L LM2 Diesel | Diagnostic Information and Procedures | Document ID: 5507731 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 DTC P21CB Reductant Control Module Supply Voltage Low Circuit/System Description For an overview of the component/system, refer to: Exhaust Aftertreatment System Description Conditions for Running the DTC DTC P10F4, P20FF = Not set Ignition = On Ignition and Start Switch Signal = Greater than 11 V Reductant Control Module Relay = On Frequency the DTC runs = Continuously — After the running conditions are met Conditions for Setting the DTC Reductant Control Module Supply Voltage = Less than a predefined threshold — For greater than 3 s Actions Taken When the DTC Sets DTCs listed in the DTC Descriptor category = Type B DTC Conditions for Clearing the DTC DTCs listed in the DTC Descriptor category = Type B DTC Reference Information Schematic Reference Engine Controls Schematics Connector End View Reference Master Electrical Component List 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 Circuit/System Verification

  1. Verify DTC P10F4, P20FF 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
  2. Verify DTC P21CB is not set. ⇒ If the DTC is set Refer to: Circuit/System Testing ⇓ If the DTC is not set
  3. All OK. Circuit/System Testing
  4. Ignition/Vehicle » Off
  5. Disconnect the electrical connector: K115 Reductant Control Module
  6. Test for battery voltage between the test points: B+ circuit terminal 1 & Ground ⇒ If less than battery voltage 3.1. Test for less than 2 Ω between the test points: B+ circuit terminal 1 & Output terminal @ F62UA Fuse ⇒ If 2 Ω or greater » Repair the open/high resistance in the circuit. ⇓ If less than 2 Ω 3.2. Remove the component: F62UA Fuse 3.3. Test for infinite resistance between the test points: B+ circuit terminal 1 @ Control module harness & Ground ⇒ If less than infinite resistance » Repair the short to ground on the circuit. ⇒ If infinite resistance » Verify the fuse is OK and there is voltage at the fuse. ⇓ If battery voltage
  7. Replace the component: K115 Reductant Control Module Repair Instructions Perform the Diagnostic Repair Verification after completing the repair: Diagnostic Repair Verification Reductant Control Module Replacement — K115 Reductant Control Module