Circuit/System Verification
WARNING: This page is about a different variant/trim than selected.
NOTE:
- Repair all fuel system related DTCs before performing this diagnostic.
- Inspect the fuel system for damage or external leaks before proceeding.
- Verify that adequate fuel is in the fuel tank before proceeding.
- The Fuel Pump Enable may need to be commanded On a few times in order to obtain the highest possible fuel pressure.
- Before proceeding with this test review the User Manual CH 48027-5 for Safety Information and Instructions.
- Ignition OFF, all accessories OFF, install a CH 48027 Gauge.
- Ignition ON, engine OFF, command the Fuel Pump Enable On several times with a scan tool.
- Verify the fuel pressure is between 345-650 kPa (50-94 psi) with the fuel pump running.
- If less than 345 kPa (50 psi)
Refer to Circuit/System Testing - Fuel Pressure Low .
- If greater than 650 kPa (94 psi)
Replace the G12 Fuel Pump.
- If between 345-650 kPa (50-94 psi)
- If less than 345 kPa (50 psi)
- Verify that the fuel pressure decreases to less than 600 kPa (87 psi) after the fuel pump is turned off.
- If greater than 600 kPa (87 psi)
Replace the G12 Fuel Pump.
- If less than 600 kPa (87 psi)
- If greater than 600 kPa (87 psi)
- Verify that the fuel pressure does not decrease more than 34 kPa (5 psi) in 1 minute.
- If greater than 34 kPa (5 psi)
Refer to Circuit/System Testing - Fuel Pressure Leaks Down .
- If less than 34 kPa (5 psi)
- If greater than 34 kPa (5 psi)
- Relieve the fuel pressure to 69 kPa (10 psi).
- Verify that the fuel pressure does not decrease more than 14 kPa (2 psi) in 5 min.
- If greater than 14 kPa (2 psi)
Replace the G12 Fuel Pump.
- If less than 14 kPa (2 psi)
- If greater than 14 kPa (2 psi)
- Engine idling at normal operating temperature.
- Verify the Fuel Pump Control Module Fuel Pressure Sensor parameter is between 300-400 kPa (43-58 psi).
- If less than 300 kPa (43 psi)
Refer to Circuit/System Testing - Fuel Pressure Low .
- If greater than 400 kPa (58 psi)
Replace the G12 Fuel Pump.
- If between 300-400 kPa (43-58 psi)
- If less than 300 kPa (43 psi)
- Operate the vehicle within the conditions of the customer's concern while monitoring the fuel pressure with the CH 48027 Gauge.
- Verify the fuel pressure does not drop off during acceleration, cruise or hard cornering.
- If the fuel pressure drops off
- If the fuel pressure does not drop off
- If the fuel system components test normal, refer to Symptoms - Engine Controls , and Fuel Injector Diagnosis .
NOTE:
DO NOT perform the Fuel System Diagnosis if the engine coolant temperature is above 60°C (150°F). High fuel pressure readings may result due to hot soak fuel boiling. With the engine OFF, the fuel pressure may increase beyond the pressure relief regulator valve's setting point of 690 kPa (100 psi) ± 5 percent.