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P1115






P1115-GENERAL TEMPERATURE RATIONALITY







Theory of Operation

The PCM compares engine coolant temperature (ECT), intake air temperature (IAT), and ambient air temperature (AAT) under cold start conditions. Following a start to run delay time, the sensor values are compared. If the sensor values are not within a specific range, the values are determined to be irrational.

- When Monitored:
With vehicle speed above 56 kph (35 mph) for more than one minute, ambient temperature above -64 C (-83 F), following an engine off period of more than 480 minutes.

- Set Condition:
The PCM compares engine coolant temperature (ECT), intake air temperature (IAT), and ambient air temperature (AAT). If none of the sensor values are within an expected range of each other, a general temperature rationality error 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.

1. DTC IS ACTIVE

NOTE: Diagnose and repair any CAN - C communication or message DTCs in any module before continuing with this procedure.

1. Turn the ignition on.
2. With the scan tool, select View DTCs and review the DTC environmental data for this DTC.

Is the good trip counter greater than 0?

Yes

- Go to 2

No

- Go to 3

2. AMBIENT AIR TEMPERATURE
1. Turn the ignition off.
2. 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.
3. Turn the ignition on.
4. 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
1. Turn the ignition off.
2. Disconnect the harness connector for the temperature sensor that was not within the specified range.
3. Turn the ignition on.
4. 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
1. Turn the ignition off.
2. Connect a jumper wire between the sensor signal circuit and the sensor ground circuit in the temperature sensor harness connector.
3. Turn the ignition on.
4. 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.PCM Verification Test

No

- Go to 5

5. TEMPERATURE SENSOR SIGNAL CIRCUIT SHORT TO GROUND
1. Turn the ignition off.
2. Disconnect the appropriate control module harness connector. Refer to the mini schematic for circuit identification.
3. Measure the resistance between ground and the temperature sensor signal circuit in the temperature sensor harness connector.

Is the resistance below 100 ohms?

Yes

- Repair the temperature sensor signal circuit for a short to ground.
- Perform the PCM Verification Test.PCM Verification Test

No

- Go to 6

6. TEMPERATURE SENSOR SIGNAL CIRCUIT SHORT TO VOLTAGE
1. Turn the ignition on.
2. Measure the voltage of the temperature sensor signal circuit in the temperature sensor harness connector.

Is there any voltage present?

Yes

- Repair the temperature sensor signal circuit for a short to voltage.
- Perform the PCM Verification Test.PCM Verification Test

No

- Go to 7

7. TEMPERATURE SENSOR SIGNAL CIRCUIT OPEN OR HIGH RESISTANCE
1. Turn the ignition off.
2. Measure the resistance of the temperature sensor signal circuit between the temperature sensor and the applicable control module.

Is the resistance below 5 ohms?

Yes

- Go to 8

No

- Repair the temperature sensor signal circuit for an open circuit or high resistance.
- Perform the PCM Verification Test.PCM Verification Test

8. TEMPERATURE SENSOR GROUND CIRCUIT OPEN OR HIGH RESISTANCE
1. Measure the resistance of the temperature sensor ground circuit between the temperature sensor and the applicable control module.

Is the resistance below 5 ohms?

Yes

- Go to 9

No

- Repair the temperature sensor ground circuit for high resistance.
- Perform the PCM Verification Test.PCM Verification Test

9. POWERTRAIN CONTROL MODULE (PCM)
1. Using the wiring diagram/schematic as a guide, inspect the wiring and connectors between the temperature sensor and the Powertrain Control Module (PCM).
2. Look for any chafed, pierced, pinched, or partially broken wires.
3. Look for broken, bent, pushed out or corroded terminals.
4. Monitor the scan tool data relative to this circuit and wiggle test the wiring and connectors.
5. Look for the data to change or for the DTC to reset during the wiggle test.
6. Search for any Technical Service Bulletins that may apply.

Were any problems found?

Yes

- Repair as necessary.
- Perform the PCM Verification Test.PCM Verification Test

No

- Replace the Powertrain Control Module (PCM).
- Perform the PCM Verification Test.PCM Verification Test

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