P1115
P1115-GENERAL TEMPERATURE RATIONALITY
For a complete wiring diagram refer to 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:
Ignition on and battery voltage greater than 10 volts.
- Set Condition:
Ambient Air, Engine Coolant, and Intake Air Temp sensor inputs are compared under cold start conditions. After start up the temp readings are monitored. If two of the three readings agree and the third doesn't, a DTC is stored. Two Trip Fault. Three good trips to turn off the MIL.
Always perform the Pre-Diagnostic Troubleshooting procedure before proceeding.
Diagnostic Test
1. ACTIVE DTC
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 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
- Refer to the INTERMITTENT CONDITION Diagnostic Procedure. Intermittent Condition
2. TEMPERATURE SENSOR READINGS
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 INTERMITTENT CONDITION Diagnostic Procedure. Intermittent Condition
No
- Go To 3
3. TEMPERATURE SENSOR
Ignition on, engine not running.
Disconnect the suspected faulty sensor.
Connect a jumper wire between the Sensor Signal circuit and the Sensor ground circuit.
With the scan tool, read the voltage of the suspected Sensor.
Did the voltage reading start at 4.8 to 5.0 volts and decrease to 0 volts when the jumper wire was installed?
Yes
- Replace the faulty Sensor.
- Perform the POWERTRAIN VERIFICATION TEST. Powertrain Verification Test
No
- Go To 4
-
NOTE: Remove the jumper wire before continuing.
4. EXCESSIVE RESISTANCE IN THE TEMPERATURE SENSOR SIGNAL CIRCUIT
NOTE: If the vehicle is equipped with ESP the AAT Sensor Signal circuit is a direct feed to the C2 BCM circuit. The PCM receives AAT Sensor Signal input over the CAN C Bus circuit. If the vehicle is not equipped with ESP, the AAT Sensor is a direct feed to the PCM.
Turn the ignition off.
Disconnect the C1 and C2 PCM harness connectors.
Disconnect the C4 TIPM 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 to perform diagnosis.
Measure the resistance of the Sensor Signal circuit from the Sensor harness connector to the appropriate terminal of special tool #8815 or the C4 TIPM 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. EXCESSIVE RESISTANCE IN THE SENSOR GROUND CIRCUIT
Measure the resistance of the Sensor ground circuit from the Sensor harness connector to the appropriate terminal of special tool #8815 or the C4 TIPM 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 6
6. PCM
NOTE: Before continuing, check the PCM harness connector terminals for corrosion, damage, or terminal push out. Repair as necessary.
Using the schematics as a guide, inspect the wire harness and connectors. Pay particular attention to all Power and Ground circuits.
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