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Home >> Lexus >> 1998 >> SC 300 >> Repair and Diagnosis >> Engine Performance >> System >> Engine Controls - Tests W/Codes >> Diagnostic Tests >> DTC P1349: Variable Valve Timing (VVT) System Malfunction >> Diagnosis & Repair (Using Lexus Scan Tool)

Diagnosis & Repair (Using Lexus Scan Tool)

  1. Check valve timing. Repair as necessary. If valve timing is okay, go to next step.
  2. Start and run engine. Allow engine to reach normal operating temperature. Connect Lexus scan tool to Data Link Connector (DLC) No. 3. See Figure. Select VVT from scan tool ACTIVE TEST menu. Using scan tool, turn OCV on and off. If engine speed does not change with OCV off and changes (rough idle) with OCV on, VVT system is okay at this time. A foreign object may have been caught in some part of VVT system. ECM will control VVT system to remove foreign object. If engine speed does not change as specified, go to next step.
  3. Start engine. Using oscilloscope, backprobing, check waveform pattern between ECM E15 harness connector terminals No. 17 (Yellow/Black wire) and No. 18 (White/Red wire). See Figure. Slowly increase engine speed. Waveform frequency "A" should lengthen as engine speed increases. See Figure. If readings are not as specified, replace ECM and retest. If readings are as specified, go to next step.
  4. Remove timing belt cover and timing belt. See ENGINES article in the ENGINE MECHANICAL section. Remove OCV. Place a shop towel under OCV cylinder head opening. Rotate VVT pulley from left to right about 30 degrees, 2-3 times. Oil should drain from OCV cylinder head opening. If oil does not drain from cylinder head opening, replace VVT pulley/gear assembly and go to next step. If oil drains from opening, go to next step.
  5. With OCV removed, connect fused jumper wires between positive battery terminal and OCV terminal No. 1, and negative battery terminal and OCV terminal No. 2. OCV plunger should move away from connector. Remove fused jumper wires. OCV plunger should move back in direction of connector. If OCV plunger does not move as specified, replace OCV and go to next step. If OCV plunger moves as specified, go to next step.
  6. Check blockage in OCV. Check oil check valve and oil pipe located under OCV. Repair an necessary. If components are okay, go to next step.
  7. Clear DTCs. See CLEARING DIAGNOSTIC TROUBLE CODES  under SELF-DIAGNOSTIC SYSTEM. Duplicate driving conditions under which DTC P1349 was set. Retrieve DTCs. See RETRIEVING DIAGNOSTIC TROUBLE CODES  under SELF-DIAGNOSTIC SYSTEM. If DTC P1349 is displayed, replace ECM and retest. If DTC P1349 is not displayed, VTT system is okay at this time. A foreign object may have been caught in some part of VVT system. ECM will control VVT system to remove foreign object.
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