P1191

P1191-INLET AIR TEMPERATURE SENSOR RATIONAL/PERFORMANCE





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

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 8 hour cold soak, the values of the Inlet Air Temperature, Engine Coolant Temperature, Intake Air Temperature and Battery Temperature sensors are compared. If the Engine Coolant, Intake Air and Battery 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 ECM will illuminate the MIL lamp after this diagnostic runs a fails in two consecutive drive cycles. The ECM 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 ECM does not read a change in value from the sensor over time. The ECM 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. 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 -15°C (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. INLET AIR TEMPERATURE SENSOR
1. After an 8 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 8 hour cold soak.

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

Yes

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

No

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