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Tahoe / Yukon Service Manual

DTC P0090-P0092, P00C8, P00C9, or P00CA

Engine Controls and Fuel - 5.3L L84 or 6.2L L87 | Diagnostic Information and Procedures | Document ID: 5403724 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 P0090 Fuel Pressure Regulator Control Circuit DTC P0091 Fuel Pressure Regulator Control Circuit Low DTC P0092 Fuel Pressure Regulator Control Circuit High DTC P00C9 Fuel Pressure Regulator High Control Circuit Low DTC P00CA Fuel Pressure Regulator High Control Circuit High Diagnostic Fault Information

Circuit Short to Ground Open/High Resistance Short to Voltage Signal Performanc
Control — Terminal 2 P0091, P00C9 P0090, P00C8 P0092, P00C9, P00CA P0089, P00C6, P228C, P228D, P2C1E, P2C1F, P2C20
Control — Terminal 1 P0091, P0092, P00C9 P0090, P00C8 P0092, P00CA P0089, P00C6, P228C, P228D, P2C1E, P2C1F, P2C20

Circuit/System Description For an overview of the component/system, refer to: Fuel System Description

Circuit Description
Control — Terminal 2 The output circuit is switched to 12 V to activate the component. The output is PWM controlled.
Circuit Description
Control — Terminal 1 The output circuit is switched to ground to activate the component. The output is PWM controlled.
Component Description
Q18 Fuel Pressure Regulator Q18 is part of the component: G18 Fuel Pump - High Pressure The fuel pressure regulator is a diaphragm relief valve. The diaphragm has fuel pressure on one side and regulator spring pressure on the other side. The fuel pressure regulator maintains the correct fuel pressure to the fuel injection system. The fuel pressure regulator delivers the needed fuel to the fuel rail. The unused fuel drops back into the reservoir of the fuel tank fuel pump module. The fuel pressure regulator is not vacuum biased. The fuel pressure regulator maintains fuel pressure in the fuel feed pipe and the fuel rail in order to prevent long cranking times.
K20 Engine Control Module The control module controls a series of actuators to ensure optimal engine performance. The control module does this by reading values from a variety of sensors, interprets the data and adjusts the engine actuators accordingly.

The fuel pressure regulator is a part of the high pressure fuel pump. The fuel pressure regulator is the solenoid valve that controls the pressure in the fuel rail. Conditions for Running the DTC Battery Voltage = Greater than 11 V Engine Speed = Greater than 50 RPM DTCs run continuously when the above conditions are met for greater than 2 s. Conditions for Setting the DTC P0090 Low Control = Open — For greater than 4 s P0091 Low Control = Short to Ground — For greater than 4 s P0092 Low Control = Short to Voltage — For greater than 4 s P00C9 High Control = Short to Ground — For greater than 4 s P00CA High Control = Short to Voltage — For greater than 4 s Actions Taken When the DTC Sets DTCs listed in the DTC Descriptor category = Type A DTC Conditions for Clearing the DTC DTCs listed in the DTC Descriptor category = Type A 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. Ignition » On / Vehicle » In Service Mode
  2. Perform the scan tool control function: Fuel Pressure Regulator » On and Off Verify the scan tool parameter: Fuel Pressure Regulator Control Circuit High Test Status = Not Run or Okay Fuel Pressure Regulator Control Circuit Open Test Status = Not Run or Okay Fuel Pressure Regulator Control Circuit Low Test Status = Not Run or Okay Fuel Pressure Regulator High Control Circuit High Test Status = Not Run or Okay Fuel Pressure Regulator High Control Circuit Open Test Status = Not Run or Okay Fuel Pressure Regulator High Control Circuit Low Test Status = Not Run or Okay ⇒ If not the specified state Refer to: Circuit/System Testing ⇓ If the specified state
  3. Operate the vehicle within the Conditions for Running the DTC. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records data.
  4. Verify the DTC does not set. ⇒ If the DTC sets Refer to: Circuit/System Testing ⇓ If the DTC does not set
  5. All OK. Circuit/System Testing
  6. Ignition/Vehicle » Off
  7. Disconnect the electrical connector: G18 Fuel Pump - High Pressure
  8. Connect a test lamp between the test points: Control circuit terminal 1 & Control circuit terminal 2
  9. Ignition » On / Vehicle » In Service Mode
  10. Perform the scan tool control function: Fuel Pressure Regulator » On and Off Verify the test lamp turns On and Off. ⇒ If the test lamp does not turn On and Off 5.1. Ignition/Vehicle » Off & Remove » Test lamp 5.2. Disconnect the electrical connector: X3 @ K20 Engine Control Module 5.3. Ignition » On / Vehicle » In Service Mode 5.4. Test for less than 1 V between the test points: Control circuit terminal 1 @ Component harness & Ground Control circuit terminal 2 @ Component harness & Ground ⇒ If 1 V or greater » Repair the short to voltage on the circuit. ⇓ If less than 1 V 5.5. Ignition/Vehicle » Off 5.6. Test for infinite resistance between the test points: Control circuit terminal 1 @ Component harness & Ground Control circuit terminal 2 @ Component harness & Ground 5.7. Test for infinite resistance between the test points: ⇒ If less than infinite resistance » Repair the short to ground on the circuit. ⇓ If infinite resistance 5.8. Test for less than 2 Ω between the test points: Control circuit terminal 2 @ Component harness & Terminal 16 @ Control module harness Control circuit terminal 1 @ Component harness & Terminal 32 @ Control module harness ⇒ If 2 Ω or greater » Repair the open/high resistance in the circuit. ⇒ If less than 2 Ω » Replace the component: K20 Engine Control Module ⇓ If the test lamp turns On and Off
  11. Test or replace the component: G18 Fuel Pump - High Pressure Component Testing
  12. Ignition/Vehicle & All vehicle systems » Off
  13. Disconnect the electrical connector: G18 Fuel Pump - High Pressure
  14. Test for 0.9 to 1.4 Ω between the test points: Control terminal 1 & Control terminal 2 ⇒ If not between 0.9 and 1.4 Ω Replace the component: G18 Fuel Pump - High Pressure ⇓ If between 0.9 and 1.4 Ω
  15. Test for infinite resistance between the test points: Each terminal of the component & The component’s housing ⇒ If less than infinite resistance Replace the component: G18 Fuel Pump - High Pressure ⇓ If infinite resistance
  16. All OK. Repair Instructions Perform the Diagnostic Repair Verification after completing the repair: Diagnostic Repair Verification Fuel Pump Replacement — Q18 Fuel Pressure Regulator For control module replacement, programming, and setup refer to: Control Module References