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System Performance Test 3 (Dwell Fixed Between 15-50 Degrees Spectrum)

  1. Run engine at part throttle for one minute. With engine at idle, note dwell. Disconnect O2 sensor and jumper ECM side of O2 sensor connector terminal to ground. See Figure .
  2. If dwell decreases, check for open circuit No. 413. If circuit No. 413 is not open, leave ECM side of O2 sensor connector grounded and check voltage from oxygen sensor to ground. If voltage is not over .8 volt, replace oxygen sensor. If over .8 volt oxygen sensor connection is at fault.
  3. If dwell did not change in step 1), jumper ECM terminal No. 3 to No. 20. If dwell decreases, circuit No. 412 is open. If dwell did not change, turn ignition on with engine stopped. Check voltage from ECM terminal No. 3 to ground.
  4. If under 4 volts, ensure connections to ECM terminals No. 17, 22, 3 and 20 are okay. If connections are okay, replace ECM. If reading was 4 volts or over in step 3), circuit No. 452 to TPS is open or coolant sensor circuit is grounded.
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