Fuel System Diagnosis - High Pressure Side

Engine Controls and Fuel - 3.0L LM2 Diesel | Diagnostic Information and Procedures | Document ID: 5401568 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 Circuit/System Description For an overview of the component/system, refer to: Fuel System Description

Component	Description
G18 Fuel Pump - High Pressure	The pump is mechanically driven by either the engine camshaft or crankshaft. The inlet feed to the high pressure pump is supplied by the fuel tank pump and the outlet of the pump is connected to the fuel rail.
K111 Fuel Pump Power Control Module	The control module contains a microprocessor used to process input data to control outputs. The control module communicates with the engine control module via serial data.

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 Scan Tool Reference Control Module References Circuit/System Verification

Note

Do NOT perform this procedure unless directed here from another procedure.

1. Engine » Cranking — For 10 s Verify the function: Engine = Running ⇒ If the function does not work Refer to: Circuit/System Testing — Test 1 ⇓ If the function works
2. Ignition/Vehicle » Off
3. Verify the condition does not exist: Fuel — Contaminated / Poor Quality » Refer to: Contaminants-in-Fuel Diagnosis ⇒ If a condition exists Repair or replace as necessary ⇓ If no condition exists
4. Engine » Running Verify the following conditions do not exist: Engine — Misfire / Reduced Engine Power / Stalling Engine Speed — Rough / Unstable Exhaust — Excessive Smoke ⇒ If a condition exists Refer to: Circuit/System Testing — Test 2 ⇓ If no condition exists
5. Refer to: Symptoms - Engine Controls Circuit/System Testing Test 1
6. Ignition/Vehicle » Off

Note

In order to perform step 2–5, the fuel temperature must be greater than 10°C (50°F) or misdiagnosis may occur. Leave the electrical connector connected.

2. Disconnect the component: Fuel Return Hose @ Q18B Fuel Pressure Regulator 2 & Plug the fuel return hose(s) in order to prevent leakage.
3. Install suitable hose to the component: Outlet @ Q18B Fuel Pressure Regulator 2 & Place the other end of the hose into a suitable container.

Note

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

4. Engine » Cranking — Until air is purged from the hose
5. Engine » Cranking — 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)
6. Ignition/Vehicle » Off
7. Install the component: Fuel Return Hose @ Q18B Fuel Pressure Regulator 2
8. Disconnect the electrical connector: Q17 Fuel Injector — All
9. 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

10. Engine » Cranking — For 15 s
11. 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
12. Ignition/Vehicle » Off
13. Install the component: Fuel Injection Fuel Return Pipe

Note

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

14. Perform the following steps: 14.1. Disconnect the electrical connector: Q17 Fuel Injector — All 14.2. Remove the component: F5BA Fuse @ X50B Battery Distribution Engine Compartment Fuse Block 14.3. Disconnect the electrical connector: E12 Glow Plug

Note

The component must be discarded whenever removed and replaced with a NEW component: 14.4. Remove the component: E12 Glow Plug — One at a time 14.5. Place and hold a clean shop towel over the component: Threaded Hole @ Cylinder Head — Glow Plug 14.6. 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

15. Test or replace the component: G18 Fuel Pump - High Pressure Test 2
16. Engine » Idling
17. 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
18. Ignition/Vehicle » Off

Note

In order to perform step 4–7, the fuel temperature must be greater than 10°C (50°F) or misdiagnosis may occur. Leave the electrical connector connected.

4. Disconnect the component: Fuel Return Hose @ Q18B Fuel Pressure Regulator 2 & Plug the fuel return hose(s) in order to prevent leakage.
5. Install suitable hose to the component: Outlet @ Q18B Fuel Pressure Regulator 2 & Place the other end of the hose into a suitable container.
6. Engine » Idling — Until air is purged from the hose
7. 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)
8. Ignition/Vehicle » Off
9. Install the component: Fuel Return Hose @ Q18B Fuel Pressure Regulator 2
10. Disconnect the electrical connector: Q17 Fuel Injector — All
11. 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

12. Engine » Cranking — For 15 s
13. 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
14. Ignition/Vehicle » Off
15. Install the component: Fuel Injection Fuel Return Pipe

Note

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

16. Perform the following steps: 16.1. Disconnect the electrical connector: Q17 Fuel Injector — All 16.2. Remove the component: F5BA Fuse @ X50B Battery Distribution Engine Compartment Fuse Block 16.3. Disconnect the electrical connector: E12 Glow Plug

Note

The component must be discarded whenever removed and replaced with a NEW component: 16.4. Remove the component: E12 Glow Plug — One at a time 16.5. Place and hold a clean shop towel over the component: Threaded Hole @ Cylinder Head — Glow Plug 16.6. 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

17. Test or replace the component: G18 Fuel Pump - High Pressure Repair Instructions Perform the Diagnostic Repair Verification after completing the repair: Diagnostic Repair Verification Fuel Injector Fuel Return Pipe Replacement Glow Plug Replacement - Cylinder 1 Glow Plug Replacement - Cylinder 2 Glow Plug Replacement - Cylinder 3 Glow Plug Replacement - Cylinder 4 Glow Plug Replacement - Cylinder 5 Glow Plug Replacement - Cylinder 6 High Pressure Diesel Fuel Injection Rail Replacement — Q18B Fuel Pressure Regulator 2 High Pressure Diesel Fuel Injector Replacement High Pressure Diesel Fuel Pump Replacement — G18 Fuel Pump - High Pressure or Q18A  Fuel Pressure Regulator 1 / Q18C Fuel Pressure Regulator 3 For control module replacement, programming, and setup refer to: Control Module References