1997 Isuzu Oasis LSFACTORY OEM SERVICE PROCEDURE

Power Steering Pressure (PSP) Switch Signal

NOTE: This signal informs PCM when power steering load is high.
  1. Turn ignition on. Measure voltage between PCM connector terminal A9 and terminal C16. See Figure. If voltage is one volt or more, go to next step. If voltage is less than one volt, go to step 3).
  2. Turn ignition off. Disconnect PSP switch 2-pin connector. Switch is located on steering gear. Connect a fused jumper wire between PSP switch harness connector terminals. Turn ignition on. Measure voltage between PCM connector terminal A9 and terminal C16. If voltage is less than one volt, replace PSP switch. If voltage is one volt or more, repair open in wire between PCM connector and PSP switch. If wire is okay, repair Black wire between PSP switch and ground connection. See WIRING DIAGRAMS article.
  3. Start engine. Turn steering wheel slowly to full lock position and release. Measure voltage between PCM connector terminal A9 and terminal C16. If battery voltage is not present, go to next step. If battery voltage is present, PSP switch signal is okay.
  4. Turn ignition off. Disconnect PSP switch 2-pin connector. Switch is located on steering gear. Turn ignition on. Measure voltage between PCM connector terminal A9 and terminal C16. If battery voltage is not present, go to next step. If battery voltage is present, replace PSP switch.
  5. Turn ignition off. Disconnect PCM 31-pin connector "C". See Figure. Check for continuity between ground and PCM connector terminal C16. If continuity exists, repair short in wire between PCM connector terminal C16 and PSP switch connector. See WIRING DIAGRAMS article. If continuity does not exist, substitute a known good PCM, then recheck for voltage. If battery voltage now exists, replace original PCM.
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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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