NGC
P1115-GENERAL TEMPERATURE RATIONALITY
For a complete wiring diagram Consult Diagrams/Electrical.
Theory of Operation
The General Temperature Rationality looks at the outputs of the three temperature sensors and compare them under cold start conditions. Following a start to run delay time, the outputs of the ambient, engine coolant, and intake air temperature sensors will be compared. If two sensors agree but not the third, the third sensor is declared as irrational. If all three sensors are irrational the General Temperature Sensor Rationality is failed.
- When Monitored:
With engine off time greater than 480 minutes and ambient temperature greater than -7° C (19.4° F).
- Set Condition:
Engine off time is greater than 480 minutes and the vehicle has been driven for one minute over 35 mph. Ambient temperature is greater than -64° C (-83° F).
Always perform the Pre-Diagnostic Troubleshooting procedure before proceeding.Initial Inspection and Diagnostic Overview
Diagnostic Test
1. DTC IS ACTIVE
NOTE: Diagnose any CAN - C Communication DTCs before continuing.
Turn the ignition off.
If possible, allow the vehicle to sit with the ignition off for more than 480 minutes in an environment where the temperature is consistent and above -7° C (19.4° F).
Test drive the vehicle. The vehicle must exceed 48 km/h (30 mph) during the test drive. Do not cycle the ignition off when the test drive is completed.
With a scan tool, select View DTCs.
Is the DTC Active or Pending at this time?
Yes
- Go to 3
No
- Go to 2
2. AMBIENT AIR TEMPERATURE
Turn the ignition off.
Allow the vehicle to sit with the ignition off in an environment where the temperature is consistent and above -7° C (19.4° F) until the engine coolant temperature is equal to ambient temperature.
Turn the ignition on.
With a scan tool, compare the AAT, ECT, and IAT sensor values.
Are all of the temperature sensor values within a range of 10° C (18° F)?
Yes
- Refer to the *CHECKING FOR AN INTERMITTENT DTC Diagnostic Procedure. Checking For An Intermittent DTC
No
- Go to 3
3. TEMPERATURE SENSOR VOLTAGE
Turn the ignition off.
Disconnect the harness connector for the temperature sensor that was not within the specified range.
Turn the ignition on.
With a scan tool, read the sensor voltage.
NOTE: The sensor voltage should be approximately 5.0 volts (plus or minus.1 volt) with the connector disconnected.
Does the scan tool display the voltage as described above?
Yes
- Go to 4
No
- Go to 5
4. TEMPERATURE SENSOR
Turn the ignition off.
Connect a jumper wire between the sensor signal circuit and the sensor ground circuit in the temperature sensor harness connector.
Turn the ignition on.
With a scan tool, read the sensor voltage.
NOTE: The sensor voltage should be approximately 0.0 volts (plus or minus.1 volt) with the jumper wire in place.
Does the scan tool display the voltage as described above?
Yes
- Replace the temperature sensor.
- Perform the PCM Verification Test. Powertrain Verification Test
No
- Go to 5
5. TEMPERATURE SENSOR SIGNAL CIRCUIT HIGH RESISTANCE
Turn the ignition off.
Connect the temperature sensor harness connector.
CAUTION: Do not probe the PCM harness connectors. Probing the PCM harness connectors will damage the PCM terminals resulting in poor terminal to pin connection. Install Miller Special Tool #8815 along with the #8815-1 to perform the diagnosis.
Using a voltmeter, perform a voltage drop test by backprobing the temperature sensor signal circuit at the temperature sensor harness connector and probing the appropriate terminal of the special tool #8815. Make sure the voltmeter leads are connected so that positive polarity is displayed on the voltmeter.
WARNING: When the engine is operating, do not stand in direct line with the fan. Do not put your hands near the pulleys, belts, or fan. Do not wear loose clothing. Failure to follow these instructions can result in personal injury or death.
Start the engine.
Is the voltage below 0.5 volts?
Yes
- Go to 6
No
- Repair the temperature sensor signal circuit for high resistance.
- Perform the PCM Verification Test. Powertrain Verification Test
6. TEMPERATURE SENSOR GROUND CIRCUIT HIGH RESISTANCE
Turn the ignition off.
CAUTION: Do not probe the PCM harness connectors. Probing the PCM harness connectors will damage the PCM terminals resulting in poor terminal to pin connection. Install Miller Special Tool #8815 along with the #8815-1 to perform the diagnosis.
Using a voltmeter, perform a voltage drop test by backprobing the temperature sensor ground circuit at the temperature sensor harness connector and probing the appropriate terminal of the special tool #8815. Make sure the voltmeter leads are connected so that positive polarity is displayed on the voltmeter.
WARNING: When the engine is operating, do not stand in direct line with the fan. Do not put your hands near the pulleys, belts, or fan. Do not wear loose clothing. Failure to follow these instructions can result in personal injury or death.
Start the engine.
Is the voltage below 0.5 volts?
Yes
- Go to 7
No
- Repair the temperature sensor ground circuit for high resistance.
- Perform the PCM Verification Test. Powertrain Verification Test
7. POWERTRAIN CONTROL MODULE (PCM)
Using the wiring diagram/schematic as a guide, inspect the wiring and connectors between the temperature sensor and the Powertrain Control Module (PCM).
Look for any chafed, pierced, pinched, or partially broken wires.
Look for broken, bent, pushed out or corroded terminals.
Monitor the scan tool data relative to this circuit and wiggle test the wiring and connectors.
Look for the data to change or for the DTC to reset during the wiggle test.
Search for any Technical Service Bulletins that may apply.
Were any problems found?
Yes
- Repair as necessary.
- Perform the PCM Verification Test. Powertrain Verification Test
No
- Replace the Powertrain Control Module (PCM).
- Perform the PCM Verification Test. Powertrain Verification Test