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Ecu Circuit Tests

NOTE: The following test is for models with separate Idle Speed Control only. For models with integral fuel injection and idle speed control systems, see FUEL INJ - BOSCH LH article in the FUEL SYSTEMS section.
  1. Locate ECU at right kick panel. Unplug both ECU harness connectors. Turn ignition on. Ensure 12 volts are present at terminal No. 1. Ensure terminal No. 2 has continuity to ground.
  2. Connect a tachometer between terminal No. 12 and ground. Start engine. Tachometer should indicate engine RPM.
  3. Some models with A/C have a White/Green or Red wire attached to terminal No. 7. If so, turn A/C on and ensure there are 12 volts present at terminal No. 7.
    NOTE: During A/C operation, the engine speed should increase about 150 RPM.
  4. Using jumper wires, connect one jumper wire between terminals No. 1 and 4. Connect another jumper wire between terminals No. 2 and 5. Start engine. If engine speed increases to 1600-2400 RPM, the ACV is okay. If not, check wiring and ACV.
  5. Repair or replace any defective components or circuits. Remove jumper wires. Connect all harness connectors. Check to see if idle speed control system is working. If not, ensure all connectors are clean and tight. If no problems are found, but idle speed control system is still working incorrectly, replace the ECU.
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