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Home >> Lexus >> 1998 >> GS 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 OBD-II Scan Tool)

Diagnosis & Repair (Using OBD-II Scan Tool)

  1. Start and run engine. Allow engine to reach normal operating temperature. 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 suspect OCV and retest.
  2. Backprobe ECM E2 and E5 connectors. Start engine. For left OCV, using oscilloscope, check waveform pattern between ECM E2 connector terminals No. 19 (Blue/Black wire) and No. 20 (White/Red wire). See Figure. For right OCV, using oscilloscope, check waveform pattern between ECM E5 connector terminals No. 19 (White/Green wire) and No. 28 (Yellow/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.
  3. Check for an open or short circuit and connector in wire harness between OCV and ECM E2 connector. Repair as necessary. If circuit and connector are okay, problem is intermittent.
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