Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
SYS.OK|MANUAL.DB● LIVE
HOMESERVICE MANUALSCHEVROLET2001CHEVY EXPRESS G3500, VAN PASSENGER EXTENDED, 6.5 FREPAIR AND DIAGNOSISEXTERNAL PAGESDIFFERENT CARSECTION 72 (ENGINE CONTROL SYSTEM TESTING & ENGINE COMPONENT TESTING)FUEL SYSTEMS (2.2L - CAVALIER CNG)FUEL PUMP RELAY DIAGNOSISTEST DESCRIPTION
2001 Chevrolet Chevy Express G3500, Van Passenger Extended, 6.5 F
Test Description
2001 Chevrolet Chevy Express G3500, Van Passenger Extended, 6.5 FSECTION Test Description
WARNING: This page does not describe the selected car, but rather 31 other vehicles, including the 2002 Saturn SL2, 2002 Saturn SL1, 2002 Saturn SL, 2002 Saturn SC2, and 2002 Saturn SC1. However, it is still accessible from the selected car via links, so may be relevant.
The numbers below refer to the step numbers in the diagnostic procedures.
- 1
The Diagnostic System Check - Engine Controls must be performed before proceeding with this diagnostic test. Failure to perform the OBD System Check will result in misdiagnosis. - 2
This step tests if the engine will start and run. A failure that causes the engine to not start on either fuel can be isolated to the CNG harness or a base vehicle problem such as a malfunctioning gasoline fuel pump relay. - 3
This step tests the gasoline control modules ability to supply power to the gasoline fuel pump circuit. - 5
This step tests for voltage through the AF fuel pump relay. With the ignition ON and the engine OFF the AF ECM does not energize the AF fuel pump relay allowing voltage to flow through the relay and energize the gasoline fuel pump. - 6
This step tests the AF ECMs ability to energize the AF fuel pump relay and disable the gasoline fuel pump during CNG operation. - 7
This step tests for stuck AF fuel pump relay contacts or a shorted AF Fuel Pump Relay control circuit. - 10
If the engine did not operate on gasoline during the Diagnostic System Check - Engine Controls but now operates on gasoline inspect for intermittent terminal contact or a AF fuel pump relay with sticking contacts that may have been disturbed during testing. - 11
This step tests if the CNG harness is the cause of the no-start on gasoline. - 15
If the Fuel Pump Power circuit tests okay there is a base vehicle problem that is causing the no-start condition.
RENDER: 1.0x
NO RELATED
Recommended Tools & Savings
Use the Manual With the Right Hardware
Pair factory procedures with proven DIY tools so the instructions are easier to execute.
Affiliate disclosure: We may earn a commission at no extra cost to you.
When to See a Mechanic
Stop DIY work and contact a certified mechanic immediately if any of the following apply:
- • You smell fuel, burning insulation, or see smoke.
- • Brakes feel soft, pull hard to one side, or make grinding noises.
- • The engine overheats, stalls repeatedly, or misfires under load.
- • You are missing required tools, torque specs, or safe lifting equipment.
- • You are not confident in the next step or safety outcome.