P1191

P1191 - INLET AIR TEMPERATURE SENSOR RATIONAL/PERFORMANCE





For a complete wiring diagram, refer to the Wiring Information.

Theory of Operation

The Inlet Air Pressure is part of the Inlet Temperature/Pressure Sensor which is located in the top of the air cleaner box. The Inlet Air Temperature Sensor performance looks at the outputs of four temperature sensors and compares them under cold start conditions. At key on after an eight hour cold soak, the values of the Inlet Air Temperature, Engine Coolant Temperature, Intake Air Temperature and EGR Orifice Temperature sensors are compared. If the Engine Coolant, Intake Air and EGR Orifice Temperature Sensors agree and the Inlet Air Temperature does not agree, the Inlet Air Temperature Sensor is declared irrational. This diagnostics also checks for a change in sensor value over a period of time. This is to verify that the sensor is responding with temperature change. The Powertrain Control Module (PCM) will illuminate the MIL lamp after this diagnostic runs and fails in two consecutive drive cycles. The PCM will turn off the MIL lamp once the diagnostic runs and passes in four consecutive drive cycles.

- When Monitored:
While the engine is running.

- Set Condition:
The Powertrain Control Module (PCM) does not read a change in value from the sensor over time. The PCM value after a cold soak for the inlet air temperature sensor varies from other engine temperature sensors.





Always perform the Pre-Diagnostic Troubleshooting procedure before proceeding. Pre-Diagnostic Troubleshooting Procedure.

1. CHECK THE INLET AIR TEMPERATURE SENSOR
1. Remove the temperature sensor and reconnect the wiring to the sensor.
2. With the scan tool in Sensors, monitor the Inlet Air Temperature.
3. While heating the sensor with an external heat source (DO NOT USE OPEN FLAME).

Does the reading from the sensor increase at least 5° F on the scan tool?

Yes

- Go To 2

No

- Replace the Inlet Air Temperature/Pressure Sensor.
- Perform the POWERTRAIN VERIFICATION TEST - 6.7L. Powertrain Verification Test.

2. CHECK THE INLET AIR TEMPERATURE SENSOR
1. After an eight hour cold soak, with the scan tool connected, monitor Inlet Air Temperature Sensor, Battery Temperature Sensor, Intake Air Temperature Sensor and Engine Coolant Temperature Sensor.

NOTE: Make sure inlet air temperature is above 20° F when performing this test.

NOTE: Make sure there is no external heat source, such as a block heater, operating during this test or within the eight hour cold soak.

Does the Inlet Air Temperature Sensor read differently from the other sensors?

Yes

- Go To 3

No

- Perform the INTERMITTENT CONDITION diagnostic procedure. . Intermittent Condition Test

3. CHECK FOR HIGH RESISTANCE IN THE (K615) INLET AIR TEMPERATURE SENSOR SIGNAL CIRCUIT
1. Disconnect the Inlet Air Temperature/Pressure Sensor harness connector.
2. Disconnect the PCM C1 harness connector.
3. Measure the resistance of the (K615) Inlet Air Temperature Sensor Signal circuit between the Inlet Air Pressure/Temperature Sensor harness connector and the PCM C1 harness connector.

Is the resistance below 5.0 Ohms?

Yes

- Replace the Inlet Air Temperature/Pressure Sensor.
- Perform the POWERTRAIN VERIFICATION TEST - 6.7L. Powertrain Verification Test.

No

- Repair the (K615) Inlet Air Temperature Sensor Signal circuit for an open or high resistance.
- Perform the POWERTRAIN VERIFICATION TEST - 6.7L. Powertrain Verification Test.