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All Models

  1. With engine hot, disconnect coolant temperature switch and charge temperature switch (6 and 8 cylinder only). Do not ground the idle stop switch. Using an accurate tachometer, maintain engine speed at 1200 RPM.
  2. Separate connector from oxygen sensor and ground the harness end. Engine speed should increase a minimum of 50 RPM, then after 15 seconds, return to 1200 RPM. On 4 cylinder engines, if engine does not respond, disconnect 4-way "T" from temperature sensor on air cleaner and allow engine to draw air. Repeat test.
  3. Hold jumper wire with 1 hand. With your other hand, touch the positive battery terminal. Engine speed should decrease at least 50 RPM. If not (on 4-cylinder engines only), disconnect 4-way "T" fitting from air cleaner temperature sensor and allow air to draw in. Repeat test.
  4. If computer fails these tests, replace it and reconnect wiring and vacuum lines.
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