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.
Engine Controls - Tests W/O Codes: Introduction
Before diagnosing symptoms or intermittent faults, perform steps in BASIC TESTING (not avalable) and TESTS W/CODES articles in the ENGINE PERFORMANCE section. Use this article to diagnose driveability problems existing when a hard fault code is not present.
Some driveability problems may have been corrected by manufacturer with a revised computer control unit. Check with manufacturer for latest computer application.
Symptom checks can direct the technician to malfunctioning components for further diagnosis. A symptom should lead to a specific component test, system test or an adjustment.
If no fault codes are present and driveability or customer complaints are present, perform functional test on ELR, EGR, and P-2 control on 5-cylinder or perform functional test on ELR and EGR on 6-cylinder. See appropriate FUNCTIONAL TEST under DIAGNOSTIC TESTS in TESTS W/CODES article in the ENGINE PERFORMANCE section.
Use the Manual With the Right Hardware
Pair factory procedures with proven DIY tools so the instructions are easier to execute.
Disclosure: Verified tool recommendations may earn an affiliate commission at no 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.