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Home >> Toyota >> 2004 >> Matrix Base, FWD, Automatic >> Repair and Diagnosis >> External Pages >> Different car >> Section 38 (Engine Controls - Self-Diagnostics) >> Diagnostic Tests >> DTC P1656: Oil Control Valve (OCV) Circuit Malfunction >> Diagnosis & Repair (Using OBD-II Scan Tool)
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Diagnosis & Repair (Using OBD-II Scan Tool)

WARNING: This page is about a different car, the 2002 Lexus IS 300. However, it is still accessible from the selected car via links, so may be relevant.
  1. Start and run engine. Allow engine to reach normal operating temperature. Disconnect OCV connector and note idle speed. Engine idle speed should not change. 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 OCV disconnected and changes (rough idle or stalls) with fused jumper wires connected, go to next step. If results are not as specified, replace OCV and retest.
  2. Access ECM under protective cover, behind left headlight in engine compartment. Backprobe ECM E7 connector. Start engine. Using oscilloscope, check waveform pattern between ECM E7 connector terminals No. 5 (Yellow/Black wire) and No. 6 (Red/Yellow wire). See Figure. Slowly increase engine speed. Waveform frequency "A" should lengthen as engine speed increases. See Figure. If waveform pattern is as shown, go to next step. If waveform pattern is not as shown, replace ECM.
  3. Check for an open or short circuit and connector in wire harness between OCV and ECM E7 connector. Repair as necessary. If circuit and connector are okay, problem is intermittent.
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