DTC P1089

Engine Controls and Fuel - 3.0L LM2 Diesel | Diagnostic Information and Procedures | Document ID: 5577836 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 P1089 Fuel Rail Pressure Performance During Deceleration Fuel Cut-Off Circuit/System Description For an overview of the component/system, refer to: Fuel System Description

Component	Description
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.
Q18A Fuel Pressure Regulator 1 & Q18C Fuel Pressure Regulator 3	The fuel pressure regulator is a solenoid valve that restricts the flow of fuel to the high pressure fuel pump and thereby controls the pressure the pump can produce. Q18A, Q18C is part of the component: G18 Fuel Pump - High Pressure
Q18B Fuel Pressure Regulator 2	The fuel pressure regulator is the solenoid valve that controls the pressure in the fuel rail.

Conditions for Running the DTC DTCs related to the following system/component = Not Set – B26 Crankshaft Position Sensor – B34 Engine Coolant Temperature Sensor – R29 Fuel Filter – Q14A Exhaust Gas Recirculation Valve 1 – Q14B Exhaust Gas Recirculation Valve 2 – Q18A Fuel Pressure Regulator 1 – Q18B Fuel Pressure Regulator 2 – Q18C Fuel Pressure Regulator 3 – Q22 Intake Manifold Tuning Solenoid Valve – Q38 Throttle Body Accelerator Pedal Position = Less than 0.05% Deceleration Fuel Cut-Off = Active — For greater than 13 s Engine = Running Engine Coolant Temperature Sensor = 68 to 126°C (154 to 259°F) Fuel Temperature Sensor = 5 to 80°C (41 to 176°F) Ignition and Start Signal = Greater than 11 V Transmission = Gear 4, 5, 6 Vehicle Speed Sensor = Greater than 0 km/h (0 MPH) Frequency the DTC runs = Continuously — After the running conditions are met Conditions for Setting the DTC

Note

Time to set this DTC may take several drive cycles — Deceleration time is cumulative Fuel Rail Pressure = Not within a calibrated range — For greater than 14 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 Diagnostic Aids A weak battery, low component/system voltage, or poor connections may cause this DTC to set. 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. Verify there are no DTCs set, except DTC P1089, related to the following system/component: Fuel System ⇒ If a related DTC is set Refer to: Diagnostic Trouble Code (DTC) List - Vehicle ⇓ If a related DTC is not set
3. Verify the following aftermarket equipment/accessories are not installed: B75 Mass Air Flow Sensor Calibration/Software Exhaust System Intake Air Duct ⇒ If aftermarket equipment/accessories are installed Repair or replace as necessary ⇓ If aftermarket equipment/accessories are not installed
4. 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. 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. Verify the following conditions do not exist: B47B Fuel Rail Pressure Sensor — Poor Connection / Skewed Fuel — Contaminated / Poor Quality » Refer to: Contaminants-in-Fuel Diagnosis & Fuel System Specifications Fuel System — Leaking » Refer to: Fuel Leak Diagnosis ⇒ If a condition exists Repair or replace as necessary ⇓ If no condition exists
8. Engine » Idling
9. Verify the scan tool parameter: Fuel Pressure Sensor = 370 to 450 kPa (54 to 65 PSI) ⇒ If less than 370 kPa (54 PSI) Refer to: Fuel System Diagnosis ⇒ If greater than 450 kPa (65 PSI) Refer to: Fuel Return System Diagnosis ⇓ If between 370 and 450 kPa (54 and 65 PSI)
10. Perform the following procedure/test: Cylinder Power Balance Test Verify the procedure/test passes. ⇒ If the procedure/test does not pass Replace the component that failed the test: Q17 Fuel Injector ⇓ If the procedure/test passes

Note

Scan Tool Device Control: Fuel Pressure Control - Regulator 1 — Controls the following components: Q18A Fuel Pressure Regulator 1 Q18C Fuel Pressure Regulator 3

6. Perform the scan tool control function: Fuel Pressure Control - Regulator 1 » Increase & Decrease Verify the scan tool parameter: Fuel Rail Pressure Sensor = The value should change with each command. ⇒ If the value does not change Replace the component: G18 Fuel Pump - High Pressure ⇓ If the value changes
7. Perform the scan tool control function: Fuel Pressure Control - Regulator 2 » Increase & Decrease Verify the scan tool parameter: Fuel Rail Pressure Sensor = The value should change with each command. ⇒ If the value does not change Replace the component: Q18B Fuel Pressure Regulator 2 ⇓ If the value changes
8. Ignition/Vehicle » Off

Note

In order to perform step 9–12, the fuel temperature must be greater than 10°C (50°F) or misdiagnosis may occur. Leave the electrical connector connected.

9. Disconnect the component: Fuel Return Hose @ Q18B Fuel Pressure Regulator 2 & Plug the fuel return hose(s) in order to prevent leakage.
10. Install suitable hose to the component: Outlet @ Q18B Fuel Pressure Regulator 2 & Place the other end of the hose into a suitable container.
11. Engine » Idling — Until air is purged from the hose
12. Engine » Idling — For 15 s Verify the container contains less than 15 mL (0.5 US fl oz) ⇒ If 15 mL (0.5 US fl oz) or greater Replace the component: Q18B Fuel Pressure Regulator 2 ⇓ If less than 15 mL (0.5 US fl oz)
13. Ignition/Vehicle » Off
14. Install the component: Fuel Return Hose @ Q18B Fuel Pressure Regulator 2
15. Disconnect the electrical connector: Q17 Fuel Injector — All
16. Disconnect the component: Fuel Injection Fuel Return Pipe @ Q17 Fuel Injector — All » Refer to: Fuel Injector Fuel Return Pipe Replacement Plug the fuel return hose(s) in order to prevent leakage. @ Diesel Fuel Separator & Fuel Rail

Note

Do NOT use the following tool or the incorrect test results will occur:Remote Start Switch

17. Engine » Cranking — For 15 s
18. Verify the condition does not exist: Leaking @ Q17 Fuel Injector ⇒ If a condition exists Replace the appropriate component: Q17 Fuel Injector ⇓ If no condition exists
19. Ignition/Vehicle » Off
20. Install the component: Fuel Injection Fuel Return Pipe

Note

Perform the following test for all 6 components. — One at a time

21. Perform the following steps: 21.1. Disconnect the electrical connector: Q17 Fuel Injector — All 21.2. Remove the component: F5BA Fuse @ X50B Battery Distribution Engine Compartment Fuse Block 21.3. Disconnect the electrical connector: E12 Glow Plug

Note

The component must be discarded whenever removed and replaced with a NEW component: 21.4. Remove the component: E12 Glow Plug — One at a time 21.5. Place and hold a clean shop towel over the component: Threaded Hole @ Cylinder Head — Glow Plug 21.6. Engine » Cranking — For 6 s Verify the condition does not exist: Fuel @ Shop Towel ⇒ If a condition exists Replace the appropriate component: Q17 Fuel Injector ⇓ If no condition exists

22. Test or replace the component: G18 Fuel Pump - High Pressure Repair Instructions Perform the Diagnostic Repair Verification after completing the repair: Diagnostic Repair Verification High Pressure Diesel Fuel Injection Rail Replacement — Q18B Fuel Pressure Regulator 2 High Pressure Diesel Fuel Injector Replacement — Q17 Fuel Injector High Pressure Diesel Fuel Pump Replacement — G18 Fuel Pump - High Pressure For control module replacement, programming, and setup refer to: Control Module References