P1115
P1115-GENERAL TEMPERATURE RATIONALITY
For a complete wiring diagram, refer to the Wiring Information.
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:
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).
- Set Condition:
Once the vehicle is soaked for a calibrated engine off time and then driven over calibrated speed and load conditions for some calibrated time, the PCM compares the ambient air, engine coolant and intake air temperature sensor values. If the values of all the three sensors disagree with one another, a general temperature sensor irrationality is declared. Two Trip Fault. Three good trips to turn off the MIL.
Always perform the Pre-Diagnostic Troubleshooting procedure before proceeding. Pre-Diagnostic Troubleshooting Procedure.
Diagnostic Test
1. ACTIVE DTC
1. Turn the ignition off.
2. 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).
3. 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.
4. With the scan tool, select View the DTCs.
NOTE: All ECT, Intake Air and Ambient Air Temperature Sensor codes must be diagnosed and repaired before continuing.
NOTE: In cold weather, this DTC could be set by a high powered block heater and no repair would be required.
Is the DTC Active or Pending at this time?
Yes
- Go To 2
No
- Perform the INTERMITTENT CONDITION diagnostic procedure. Intermittent Condition Test.
2. TEMPERATURE SENSOR CIRCUIT
1. With the scan tool, read the ECT, Ambient Air Temp and Intake Air Temp Sensor temp values.
2. Start the engine.
3. Allow the engine to reach normal operating temperature while monitoring the three Sensor temperature values.
Is the temperature for each of the Sensors increasing properly?
Yes
- Perform the INTERMITTENT CONDITION diagnostic procedure. Intermittent Condition Test.
No
- Go To 3
3. TEMPERATURE SENSOR
1. Disconnect the suspected sensor.
2. Ignition on, engine not running.
3. With the scan tool, read the voltage of the suspected sensor.
4. Connect a jumper wire between the Sensor Signal circuit and the Sensor ground circuit.
Did the voltage reading start at 4.8 to 5.0 Volts and decrease to 0 Volts when the jumper wire was installed?
Yes
- Verify that there is good pin to terminal contact in the Sensor and Control Module connectors. If OK, replace the appropriate Temperature Sensor.
- Perform the POWERTRAIN VERIFICATION TEST. Powertrain Verification Test.
No
- Go To 4
NOTE: Remove the jumper wire before continuing.
4. CHECK THE TEMPERATURE SENSOR SIGNAL CIRCUIT FOR EXCESSIVE RESISTANCE
1. Turn the ignition off.
2. Disconnect the PCM harness connector.
3. Measure the resistance of the Sensor Signal circuit from the Sensor harness connector to the PCM harness connector for the ECT Sensor and IAT Sensor.
4. Measure the resistance of the AAT Sensor Signal circuit from the Sensor harness connector to the BCM harness connector.
Is the resistance above 5.0 Ohms?
Yes
- Repair the excessive resistance in the Temperature Sensor Signal circuit.
- Perform the POWERTRAIN VERIFICATION TEST. Powertrain Verification Test.
No
- Go To 5
5. CHECK THE SENSOR GROUND CIRCUIT FOR EXCESSIVE RESISTANCE
1. Measure the resistance of the Sensor ground circuit from the ECT Sensor and IAT Sensor to the PCM harness connector.
2. Measure the resistance of the Sensor ground circuit from the AAT Sensor harness connector to the BCM harness connector.
Is the resistance above 5.0 Ohms?
Yes
- Repair the excessive resistance in the Sensor ground circuit.
- Perform the POWERTRAIN VERIFICATION TEST. Powertrain Verification Test.
No
- Go To 9
6. CHECK THE SENSOR SIGNAL CIRCUIT FOR A SHORT TO GROUND
1. Measure the resistance between ground and the Sensor Signal circuit at the Sensor harness connector.
Is the resistance below 100 Ohms?
Yes
- Repair the short to ground in the Sensor Signal circuit.
- Perform the POWERTRAIN VERIFICATION TEST. Powertrain Verification Test.
No
- Go To 7
7. CHECK FOR THE SENSOR SIGNAL CIRCUIT SHORTED TO THE SENSOR GROUND CIRCUIT
1. Measure the resistance between ground and the Sensor Signal circuit at the Sensor harness connector.
Is the resistance below 100 Ohms?
Yes
- Repair the short between the Sensor ground circuit and the Sensor Signal circuit.
- Perform the POWERTRAIN VERIFICATION TEST. Powertrain Verification Test.
No
- Go To 8
8. CHECK THE SENSOR SIGNAL CIRCUIT FOR A SHORT TO VOLTAGE
1. Turn the ignition on.
2. Measure the voltage on the Sensor Signal circuit at the Sensor harness connector.
Is there any voltage present?
Yes
- Repair the short to voltage in the Sensor Signal circuit.
- Perform the POWERTRAIN VERIFICATION TEST. Powertrain Verification Test.
No
- Go To 9
9. POWERTRAIN CONTROL MODULE (PCM)
1. Turn the ignition off.
2. Using the wiring diagram/schematic as a guide, inspect the wiring and connectors between the related Sensors and the Powertrain Control Module (PCM).
3. Look for any chafed, pierced, pinched or partially broken wires.
4. Look for broken, bent, pushed out or corroded terminals. Verify that there is good pin to terminal contact in the related Sensor and Powertrain Control Module connectors.
5. Perform any Technical Service Bulletins that may apply.
Were there any problems found?
Yes
- Repair as necessary.
- Perform the POWERTRAIN VERIFICATION TEST. Powertrain Verification Test.
No
- Replace and program the Powertrain Control Module.
- Perform the POWERTRAIN VERIFICATION TEST. Powertrain Verification Test.