P0072

P0072-INLET AIR TEMP SENSOR VOLTAGE TOO LOW







WHEN MONITORED
With the ignition on and battery voltage greater than 10.4 volts.

SET CONDITION
The circuit voltage to the ECM falls below a calibrated threshold for a certain period of time.

POSSIBLE CAUSES
- Sensor out of spec
- Harness shorted (sensor side)
- (Y501) 5-Volt supply open
- Harness shorted (ECM side)
- Intermittent condition
- ECM

Always perform the Pre-Diagnostic Troubleshooting procedure before proceeding.

Diagnostic Test

1. INLET AIR TEMP SENSOR OUT OF SPEC
Turn the ignition off.
Disconnect the Inlet Air Temp sensor harness connector.
Check connectors - Clean/repair as necessary.
Measure the resistance of the temperature sensor.

Q: Is the resistance between 300 and 90k ohms?

YES: Go To 2
NO: Replace the sensor. Perform the POWERTRAIN VERIFICATION TEST VER - 1 (DIESEL). Powertrain Verification Test - Ver 1

2. INTERMITTENT CONDITION
Reconnect the Inlet Air Temp Sensor harness connector.
Turn the ignition on.
With the scan tool, erase DTCs.
With the scan tool, read DTCs.

Q: Did the DTC return?

YES: Go To 3
NO: Refer to the INTERMITTENT CONDITION Symptom (Diagnostic Procedure).

3. HARNESS SHORTED (INLET AIR TEMPERATURE SENSOR SIDE)





Turn the ignition off.
Disconnect the inlet Air Temp sensor harness connector.
Disconnect the ECM harness connector.
Check connectors - Clean/repair as necessary.
Measure the resistance between the engine ground and the (K615) temperature sensor signal circuit at the sensor connector.

Q: Is the resistance more than 100 k ohms?

YES: Go To 4
NO: Repair or replace the Engine harness shorted. Perform the POWERTRAIN VERIFICATION TEST VER - 1 (DIESEL). Powertrain Verification Test - Ver 1

4. HARNESS SHORTED (ECM SIDE)





Measure the resistance between the (K615) signal circuit and all other circuits at the ECM harness connector.

Q: Is the resistance more than 100 k ohms?

YES: Go To 5
NO: Repair or replace the ECM harness shorted. Perform the POWERTRAIN VERIFICATION TEST VER - 1 (DIESEL). Powertrain Verification Test - Ver 1

5. (K668) 5-VOLT SUPPLY CIRCUIT





Reconnect the ECM harness connector.
Turn the ignition on.
Measure the voltage between the (K668) supply circuit and the (K690) return circuit in the Air Temp sensor harness connector.

Q: Is the voltage between 4.5 and 5.5 volts?

YES: Go To 6
NO: Go To 7

6. ECM
Reconnect the Air Temp sensor harness connector.
Reconnect the ECM harness connector.
With the scan tool, erase DTCs.
While monitoring with scan tool, disconnect the Air Temp sensor harness connector.

Q: Did the DTC P0073 set?

YES: Refer to the INTERMITTENT CONDITION Symptom (Diagnostic Procedure)
NO: Replace the ECM. Perform the POWERTRAIN VERIFICATION TEST VER - 1 (DIESEL). Powertrain Verification Test - Ver 1

7. (K668) 5-VOLT SUPPLY OPEN





Disconnect the ECM harness connectors.
Measure the voltage at the (K668) 5-volt supply circuit at the ECM harness connector.

Q: Is the voltage between 4.5 and 5.5 volts?

YES: Fix or repair the (K668) 5-volt supply circuit shorted to voltage. Perform the POWERTRAIN VERIFICATION TEST VER - 1 (DIESEL). Powertrain Verification Test - Ver 1
NO: Replace the ECM. Perform the POWERTRAIN VERIFICATION TEST VER - 1 (DIESEL). Powertrain Verification Test - Ver 1