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Home >> Mitsubishi >> 1999 >> 3000GT Base, Automatic >> Repair and Diagnosis >> Engine Performance >> System >> Engine Controls - Self-Diagnostics >> Diagnostic Tests >> DTC P0551: Power Steering Pressure (PSP) Sensor Circuit Performance >> Diagnostic Procedure
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Diagnostic Procedure

NOTE: For terminal identification, see TERMINAL IDENTIFICATION in SELF-DIAGNOSTICS - INTRODUCTION article. For circuit and wire color identification, see WIRING DIAGRAMS article.
  1. Using scan tool, read data list item No. 27 (power steering pressure switch). Switch status should read ON when steering wheel is turned. Switch status should read OFF when steering wheel is centered. If switch status is as specified, fault is intermittent. See INTERMITTENT DTCS  under CIRCUIT TESTS. If switch status is not as specified, go to next step.
  2. Disconnect pressure hose from oil pump. See Fig 1. Install Adapter (MB990993) on oil pump. Install Adapter (MB990994) on disconnected hose. Connect Pressure Gauge (MB990662) and shutoff valve between adapters. Open shutoff valve. Bleed steering hydraulic system. See appropriate POWER STEERING article in STEERING. Go to next step.
  3. Install a thermometer in fluid reservoir. Start engine and allow it to idle. Turn steering wheel several times until fluid temperature reaches 122-140°F (50-60°C). Disconnect PSP switch connector. Install a DVOM between ground and PSP switch terminal. See Fig 1. Note continuity reading on DVOM. Go to next step.
  4. With engine idling, gradually close shutoff valve to increase power steering system pressure. Check pressure when PSP switch is actuated by watching for a change in continuity. PSP switch should be actuated when pressure is 213-284 psi. Gradually open shutoff valve to decrease pressure. Check pressure when PSP switch is de-actuated. PSP switch should de-actuate at 100-171 psi. Turn engine off. If PSP operates as specified, go to next step. If PSP does not operate as specified, replace PSP switch. Go to step  7.
  5. Disconnect PSP switch connector. On 3000GT, go to next step. On Montero, turn ignition off. Disconnect ECM connector. Ground ECM connector terminal No. 54. Using DVOM, check continuity between chassis ground and PSP switch connector. If continuity does not exist, repair wiring harness as necessary. If continuity exists, go to next step.
  6. Turn ignition on. Using DVOM, check voltage between ground and PSP switch connector. If battery voltage does not exist, replace ECM. If battery voltage exists, go to next step.
  7. Verify repair. Ensure scan tool displays OFF when steering wheel is centered, and ON when steering wheel is turned.
Fig 1: Testing Power Steering Pressure (PSP) Switch Sensor Circuit
G97B06408Courtesy of MITSUBISHI MOTOR SALES OF AMERICA.
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