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.
Diagnostic Procedure
- Perform On-Board Diagnostics II (OBD-II) System Check. See SELF-DIAGNOSTICS - INTRODUCTION article. Retrieve and record FREEZE FRAME and/or FAIL RECORDS data for each DTC set. Go to next step.
- Check engine coolant temperature. If coolant temperature is greater than 201°F (94°C), allow engine to cool to below specified temperature and go to next step. If coolant temperature is 201°F (94°C) or less, go to next step.
- Turn ignition off. Connect fuel pressure gauge to test port on injector rail. Turn ignition on, with engine off. Using scan tool, energize fuel pump. Place bleed hose of fuel pressure gauge in container. Bleed air from hose. Energize fuel pump. Continue to energize fuel pump until highest pressure is observed. If fuel pressure is 60-65 psi (414-455 kPa), go to next step. If fuel pressure is not within specifications, see appropriate FUEL SYSTEM DIAGNOSIS procedure in BASIC DIAGNOSTIC PROCEDURES article.
- Inspect fuel pressure once fuel pump stops operating. If fuel pressure remains at 55-60 psi (379-414 kPa), go to next step. If fuel pressure does not remain within specification, see appropriate FUEL SYSTEM DIAGNOSIS procedure in BASIC DIAGNOSTIC PROCEDURES article.
- Turn ignition off. Turn ignition on, with engine off. Using scan tool, select SPECIAL FUNCTIONS. Select FUEL SYSTEMS, INJECTOR BALANCE TEST. Select specific injector to test and press ENTER. Record fuel pressure (first reading) once pressure is stabilized. Press Pluse Injector button to energize fuel injector. Record fuel pressure (second reading) once pressure is stabilized.
Press ENTER on scan tool. Select next injector and proceed with INJECTOR BALANCE TEST. Record first and second pressure readings. Continue for remaining injectors. Subtract second pressure reading from 1st reading for each injector. The difference in readings is pressure drop.
Add all pressure drop values to obtain total pressure drop. Divide total pressure drop by number of fuel injectors. If any individual injectors pressure drop are greater or less than 1.5 psi (10 kPa) compared against average pressure drop, go to next step. If all individual injectors pressure drop is within specification, go to FUEL INJECTOR COIL TEST .
- Retest suspect injector(s) that is not within fuel drop average specification. If suspect injector(s) is still not within specification after retesting, replace injector. If suspect injector(s) is within specification after retesting, go to FUEL INJECTOR COIL TEST .
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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.
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