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Home >> Lexus >> 1998 >> SC 400 >> Repair and Diagnosis >> Engine Performance >> System >> Engine Controls - Tests W/Codes >> Diagnostic Tests >> DTC P1656 Or P1663: Oil Control Valve (OCV) >> Diagnosis & Repair (Using Lexus Scan Tool)

Diagnosis & Repair (Using Lexus Scan Tool)

  1. 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.
  2. 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. With engine running. Disconnect suspect OCV connector. Connect fused jumper wires between positive battery terminal and OCV connector terminal No. 1, and negative battery terminal and OCV connector terminal No. 2. See Figure. If engine speed does not change with suspect OCV disconnected and changes (rough idle) with fused jumper wires connected, go to next step. If results are not as specified, replace OCV and retest.
  4. Backprobe ECM E15 and E18 connectors. Start engine. For left OCV, using oscilloscope, check waveform pattern between ECM E15 connector terminals No. 19 (Red/Black wire) and No. 20 (Black/White wire). See Figure. For right OCV, using oscilloscope, check waveform pattern by backprobing between ECM E18 connector terminals No. 19 (White/Red wire) and No. 28 (Green/Yellow wire). See Figure.
  5. 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.
  6. Check for an open or short circuit and connector in wire harness between suspect OCV and ECM E15 or ECM E18 connector. Repair as necessary. If circuits and connectors are okay, problem is intermittent.
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