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Circuit Test A3

NOTE: Perform this test when check of VREF circuit has failed, or directed here by a sensor test or other CIRCUIT TEST.
Fig 1: Reference Voltage Circuits
G108546
  1. Checking Battery Power Circuit. Disconnect ECA 60-pin connector. Inspect connector for damaged pins, corrosion, or loose wires. Repair if necessary. Install breakout box, leaving ECA connected. Turn key on, leaving engine off. Set DVOM on 20-volt scale and measure voltage between test pin No. 37 and SIGNAL RETURN in SELF-TEST connector. If reading is less than 10.5 volts, go to CIRCUIT TEST D23 , step 1) for 3.8L FWD SEFI and 3.8L SC SEFI engines. If reading is less than 10.5 volts, go to CIRCUIT TEST A2 , step 1) for all other engines. If reading is 10.5 volts or more, go to next step.
  2. Checking VREF Voltage. With breakout box installed and ECA connected, turn key on, leaving engine off. Set DVOM on 20-volt scale and measure voltage between test pins No. 26 and 46. If reading is 6 volts or more, go to step 4). If reading is 4 volts or less, go to step 5). If reading is between 4 and 6 volts, go to next step.
  3. VREF and Signal Return Continuity. With breakout box installed and ECA disconnected, turn key off. If directed here by a sensor test, ensure that sensor is disconnected. Set DVOM on 200-ohm scale. Measure resistance from test pins No. 26 and 46 to suspect VREF sensor harness connector. If both readings are less than 5 ohms, VREF voltage is okay. Connect all sensors and repeat QUICK TEST. If any reading is 5 ohms or more, repair open circuit in VREF or signal return and then repeat QUICK TEST.
  4. Checking For Excess VREF Circuit Voltage. Turn key off and wait 10 seconds. With breakout box installed and ECA disconnected, turn key on, leaving engine off. Set DVOM on 20-volt scale and measure voltage between test pin No. 26 and battery ground. If reading is less than 0.5 volt, replace ECA and repeat QUICK TEST. If reading is 0.5 volt or more, repair short to battery power in EEC harness. Repeat QUICK TEST. Replace ECA if fault still occurs.
  5. Shorted TPS Sensor. Turn key off and wait for 10 seconds. With breakout box installed and ECA connected, disconnect Throttle Position Sensor (TPS) from vehicle harness. Turn key on, leaving engine off. Set DVOM on 20-volt scale and measure voltage between test pins No. 26 and 46. If reading is 4 volts or more, replace TPS and repeat QUICK TEST. If less than 4 volts on models with EVP/PFE sensor, go to next step. If reading is less than 4 volts on all other models, go to step 7).
  6. Shorted EVP/PFE Sensor. Turn key off and wait 10 seconds. With breakout box installed and ECA connected, disconnect EVP/PFE sensor. Turn key on, leaving engine off. Set DVOM on 20-volt scale. Measure voltage between test pins No. 26 and 46. If reading is 4 volts or more, replace EVP/PFE sensor and repeat QUICK TEST. If reading is less than 4 volts, go to next step. 6 7) Shorted MAP/BP Sensor. Turn key off and wait 10 seconds. With breakout box installed and ECA connected, disconnect MAP/BP sensor. Turn key on, leaving engine off. Set DVOM on 20-volt scale. Measure voltage between test pins No. 26 and 46. If reading is 4 volts or more, replace MAP/BP sensor and repeat QUICK TEST. If reading is less than 4 volts on models without Vane Airflow (VAF) sensor, go to step 9). If reading is less than 4 volts on models with VAF sensor, go to next step.
  7. Shorted VAF Sensor. Turn key off and wait 10 seconds. With breakout box installed and ECA connected, disconnect VAF sensor. Turn key on, leaving engine off. Set DVOM on 20-volt scale. Measure voltage between test pins No. 26 and 46. If reading is 4 volts or more, replace VAF sensor and repeat QUICK TEST. If reading is less than 4 volts, go to next step.
  8. VREF Shorted to Ground. With breakout box installed and ECA disconnected, turn key off and wait 10 seconds. Disconnect TPS, MAP/BP, EVP/PFE, and VAF sensor (if equipped). Set DVOM on 200-ohm scale. Measure resistance between test pin No. 26 and test pins No. 20, 40, 46, and 60. If any resistance is less than 5 ohms, repair short to ground, connect all sensors and repeat QUICK TEST. If original problem still occurs, replace ECA and repeat QUICK TEST. If reading is 5 ohms or more, connect sensors, replace ECA and repeat QUICK TEST.
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