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Home >> Chevrolet >> 2006 >> Uplander Base >> Repair and Diagnosis >> Engine Performance >> System >> Engine Controls - 3.5L - DTC P0016 To DTC P0206 >> DTC P0116, P0125 or P0128 >> Circuit/System Testing

Circuit/System Testing

P0116

    IMPORTANT: The cooling fans are commanded ON when certain ECT DTCs are set.
  1. Inspect the cooling system coolant level. If low, then refer to Loss of Coolant .
  2. Observe and record the ambient air temperature of the vehicle environment using an accurate thermometer.
    3. IMPORTANT: The vehicle needs to have been OFF for at least 8 hours for the ECT and the IAT to be at ambient temperature. The vehicle should not have changed environments during this time.
  3. After the vehicle has been OFF for 8 hours, remove the mass air flow (MAF)/IAT sensor.
  4. Remove the ECT sensor.
  5. Place the sensors on a work surface away from any heat source. Allow the sensors to reach the ambient air temperature for 30-60 minutes.
  6. Connect the MAF/IAT sensor and the ECT sensor to the electrical connector, but DO NOT install them. Insulate the sensors from any engine heat source.
    7. IMPORTANT: The IAT sensor will start to warm-up as soon as the ignition is turned ON.
  7. Turn ON the ignition and take a snapshot of the Engine Data List with a scan tool. Refer to Scan Tool Snapshot Procedure .
  8. Review the snapshot data that was taken with the scan tool. Observe the ECT Sensor and IAT Sensor parameters with a scan tool. Is the difference between the ECT Sensor parameter and the IAT Sensor parameter more than 15°C (27°F)?
  9. Observe the recorded IAT Sensor and ECT sensor parameters. Is the difference between the IAT Sensor, ECT Sensor parameters and the ambient air temperature less than 8°C (14°F)?
  10. Disconnect the MAF/IAT sensor. Test for an intermittent and for a poor connection at the IAT sensor. Refer to Testing for Intermittent Conditions and Poor Connections .
  11. At the sensor, measure the resistance between the IAT signal and the IAT low reference terminals with a DMM and record the value. Observe the recorded ambient air temperature. Compare the resistance measurement of the IAT sensor to the ambient air temperature using the Temperature vs Resistance .
    • If not within specified range, then replace the MAF/IAT sensor.
  12. Disconnect the ECT sensor and inspect for the ECT sensor leaking engine coolant internally through the sensor, corrosion on the ECT sensor terminals or for corrosion on the ECT harness connector terminals.
    13. IMPORTANT: DO NOT hold the ECT sensor by the probe.
  13. At the sensor, measure the resistance between the ECT signal and the ECT low reference terminals with a DMM and record the value. Observe the recorded ambient air temperature. Compare the resistance measurement of the ECT sensor to the ambient air temperature using the Temperature vs Resistance .
    • If not within specified range, then replace the ECT sensor.
  14. Measure for 4.8-5.2 volts from the IAT signal circuit to a good ground with a DMM.
    • If not within specified range, then test the IAT signal circuit for a high resistance or for an intermittent and for a poor connection at the control module. If circuits test OK, then replace the control module.
  15. Turn OFF the ignition for 90 seconds to allow the control modules to power down.
  16. Measure for 4.8-5.2 volts from the ECT signal circuit to a good ground with a DMM.
    • If within the specified range, then go to intermittent conditions.
    • If NOT within specified range, then test the ECT signal circuit for a high resistance or short to ground or for shorted terminals and poor connections at the control module. If circuits test OK, then replace the control module.
    17. IMPORTANT:
    • All electrical components and accessories must be turned OFF.
    • Performing this step will disable the diagnostic for 8 hours.
  17. Measure for 5 ohms of resistance from the low reference circuit of the IAT sensor to a good ground with a DMM.
    • If less than 5 ohms, then go to Testing for Intermittent Conditions and Poor Connections .
    • If more then 5 ohms, then test the IAT low reference circuit for high resistance or for an intermittent and for a poor connection at the control module. If circuits test OK, then replace the control module.

P0125 or P0128

    IMPORTANT: The cooling fans are commanded ON when certain ECT DTCs are set.
  1. Inspect the cooling system coolant level. If low, then refer to Loss of Coolant .
  2. Inspect for the following conditions:
    • Corrosion on the ECT terminals
    • Improper or corroded terminals at the ECT harness connector
    • Loose terminals in the ECT harness connector
  3. Measure for 4.8-5.2 volts from the signal circuit of the ECT sensor to a good ground with a DMM.
    • If not within specified range, test the ECT sensor signal circuit for high resistance or for an intermittent and for a poor connection at the control module. If circuits test OK, then replace the control module.
  4. Measure for 4.8-5.2 volts from the signal circuit of the ECT sensor to the low reference circuit of the ECT sensor with a DMM.
    • If not within specified range, test the ECT sensor low reference circuit for high resistance or for an intermittent and for a poor connection at the control module.
    • If circuits test OK, then replace the control module.
  5. Turn OFF the ignition. Remove the ECT sensor. Place the sensor on a work surface away from any heat source.
  6. Allow the sensor to reach ambient air temperature for 30-60 minutes.
  7. Observe and record the ambient air temperature of the vehicle environment using an accurate thermometer.
    8. IMPORTANT: DO NOT hold the ECT sensor by the probe.
  8. At the sensor, measure the resistance between the ECT signal and the ECT low reference terminals with a DMM and record the value.
  9. Compare the resistance measurement of the ECT sensor to the ambient air temperature on the Temperature vs Resistance .
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