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 Procedures
1996 Isuzu Trooper S, AutomaticSECTION Diagnostic Procedures
WARNING: This page is about a different car, the 1996 Honda Passport. However, it is still accessible from the selected car via links, so may be relevant.
- Perform On-Board Diagnostic (OBD) System Check. Read and record FREEZE FRAME and/or FAIL RECORDS data for each DTC set. Go to next step.
- If any other component-related DTCs are set, fix those DTCs first. If no other DTC is present, go to next step.
- Check fuel level. Add fuel if tank is almost empty. If fuel was added, go to next step. If no additional fuel was required, go to step 5).
- Start vehicle and bring engine to normal operating temperature (167-203°F or 75-95°C). Raise engine speed to 1200 RPM and using scan tool observe HO2S 1 voltage. If scan tool reading toggle between .1-.9 volts, see appropriate INJECTOR BALANCE TEST in SYSTEM/COMPONENT TESTS - 2.6L 4-CYL article. If voltage is not as specified, go to next step.
- Turn ignition off. Relieve fuel pressure and install fuel pressure gauge. Start engine, bring to normal operating temperature and allow to idle. Disconnect vacuum line going to fuel pressure regulator and read pressure gauge. If pressure is between 41-47 PSI, see OBD II SYSTEM CHECK in BASIC TESTING - 2.6L 4-CYL . If pressure reading is not as specified, go to next step.
- Check for restricted fuel lines or filter. if problem is found, repair problem and go to step 9). If no problem is found, go to next step.
- Turn ignition on, engine off. Using scan tool, turn on fuel pump. With fuel pressure gauge still connected, pinch off fuel return line, not allowing fuel pressure to exceed 60 PSI. Manipulate fuel line to rase pressure above 47 PSI. If pressure rises above 47 PSI, go to DIAGNOSTIC AIDS . If pressure does not rise to 47 PSI, go to next step.
- Check for faulty fuel pump, restricted fuel pump strainer, incorrect fuel pump, incorrect fuel being used or hot fuel. If any problem is found, repair as necessary and go to next step.
- Read and record FAIL RECORDS data for DTC P1171. Operate vehicle within conditions noted in FAIL RECORDS data. Using scan tool, read SPECIFIC DTC. If scan tool displays DTC P1171 FAILED THIS IGN, return to step 2). If scan tool does not display DTC P1171 FAILED THIS IGN, repair is complete.
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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.