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Home >> Jeep >> 2000 >> Cherokee Classic, 4D Utility, 4WD, Part Time >> Repair and Diagnosis >> Engine Performance >> System >> Engine Controls - Self Diagnostics >> Diagnostic Tests >> DTC P0551: Power Steering Switch Failure (2.5L) >> Testing

DTC P0551: Power Steering Switch Failure (2.5L): Testing

  1. Start engine and allow it to idle. Using scan tool, monitor P/S pressure switch state. Turn steering wheel to extreme left and right. If P/S pressure switch state changes, go to next step. If P/S pressure switch state does not change, go to step  4 .
  2. Ensure engine is still running. Using scan tool, monitor P/S pressure switch state while wiggling wiring harness from P/S pressure switch to PCM. P/S pressure switch is attached to power steering high pressure hose at pump and has a Black 2-pin connector. PCM is located in engine compartment on left front fender, near radiator support. If P/S pressure switch state changes while wiggling wiring harness, repair wiring harness where wiggling caused P/S pressure switch state to change. If P/S pressure switch state does not change, go to next step.
  3. Turn ignition off. Visually inspect related connectors and wiring harness for damage. Repair connectors and wiring harness as necessary. If connectors and wiring harness are okay, no problem is indicated at this time. Test is complete.
  4. Turn ignition off. Disconnect P/S pressure switch connector. P/S pressure switch is attached to power steering high pressure hose at pump and has a Black 2-pin connector. Inspect connector for damaged pins, corrosion and loose terminals. Repair connector as necessary. If connector is okay, connect one end of a jumper wire to Dark Blue/Brown wire at P/S pressure switch connector. Turn ignition on, with engine off. Using scan tool, monitor P/S pressure switch. Touch other end of jumper wire to ground 5 times. If P/S pressure switch state changes, go to next step. If P/S pressure switch state does not change, go to step  7 .
  5. Turn ignition off. Measure resistance between ground and Black wire at P/S pressure switch connector. If resistance is less than 5 ohms, go to next step. If resistance is 5 ohms or more, repair open in Black wire between ground connection and P/S switch. See WIRING DIAGRAMS article.
  6. At this time, P/S pressure switch is assumed to be defective. Replace P/S pressure switch.
  7. Ensure ignition is off. Ensure P/S pressure switch connector is still disconnected. Disconnect PCM connectors. PCM is located in engine compartment on left front fender, near radiator support. Inspect connectors for damaged pins, corrosion and loose terminals. Repair connectors as necessary. If connectors are okay, measure resistance between ground and Dark Blue/Brown wire at P/S pressure switch connector. If resistance is 5 ohms or more, go to next step. If resistance is less than 5 ohms, repair short to ground in Dark Blue/Brown wire between P/S pressure switch and PCM.
  8. Measure resistance of Dark Blue/Brown wire between P/S pressure switch connector and terminal No. 12 at PCM C1 connector. See Figure . If resistance is less than 5 ohms, go to next step. If resistance is 5 ohms or more, repair open in Dark Blue/Brown wire between P/S pressure switch sense and PCM.
  9. At this time, PCM is assumed to be defective. Replace PCM.
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