P1115
P1115-GENERAL TEMPERATURE RATIONALITYP1115-General Temperature Rationality:
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.
POSSIBLE CAUSES
- Excessive resistance in the sensor signal circuit
- Excessive resistance in the sensor ground circuit
- Temperature sensor
- PCM
Always perform the Pre-Diagnostic Troubleshooting procedure before proceeding.
Diagnostic Test
1. ACTIVE DTC
Ignition on, engine not running.
With a scan tool, read the DTCs.
NOTE:
- All ECT, Intake Air, and Ambient Air Temperature Sensor codes must be diagnosed and repaired before continuing.
- In cold weather, this DTC could be set by a high powered block heater and no repair would be required.
Q: Is the DTC active at this time?
YES: Go To 2
NO: Refer to the INTERMITTENT CONDITION Diagnostic Procedure. Component Tests and General Diagnostics
Perform the POWERTRAIN VERIFICATION TEST. Powertrain Verification Test
2. TEMPERATURE SENSOR CIRCUIT
With a scan tool, read the ECT, Ambient Air Temp, and Intake Air Temp Sensor temp values.
Start the engine.
Allow the engine to reach normal operating temperature while monitoring the three Sensor temperature values.
Q: Is the temperature for each of the Sensors increasing properly?
YES: Refer to the INTERMITTENT CONDITION Diagnostic Procedure. Component Tests and General Diagnostics
Perform the POWERTRAIN VERIFICATION TEST. Powertrain Verification Test
NO: Go To 3
3. TEMPERATURE SENSOR
Ignition on, engine not running.
Disconnect the suspected 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.
Q: 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 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
Turn the ignition off.
Disconnect the C2 PCM harness connector.
Disconnect the C2 FCM 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 for the ECT Sensor and IAT Sensor.
Measure the resistance of the (G31) AAT Sensor Signal circuit from the Sensor harness connector to the C2 FCM harness connector.
Q: 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 (K900) Sensor ground circuit from the ECT Sensor and IAT Sensor to the appropriate terminal of special tool #8815.
Measure the resistance of the (G931) Sensor ground circuit from the AAT Sensor harness connector to the C2 FCM harness connector.
Q: 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.
Q: 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