Page 474 of 5267
P0072-INLET AIR TEMP SENSOR VOLTAGE TOO LOW
For a complete wiring diagramRefer to Section 8W.
Page 475 of 5267

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)
(K668) 5-VOLT SUPPLY OPEN
HARNESS SHORTED (ECM SIDE)
INTERMITTENT CONDITION
ECM
Always perform the Pre-Diagnostic Troubleshooting procedure before proceeding. (Refer to 9 - ENGINE -
DIAGNOSIS AND TESTING)
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.
Is the resistance between 300 and 90k ohms?
Ye s>>
Go To 2
No>>
Replace the sensor.
Perform POWERTRAIN VERIFICATION TEST VER - 1 (DIESEL). (Refer to 9 - ENGINE- DIAGNOSIS
AND TESTING)
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.
Did the DTC return?
Ye s>>
Go To 3
No>>
Refer to the INTERMITTENT CONDITION Symptom (Diagnostic Procedure). (Refer to 9 - ENGINE -
DIAGNOSIS AND TESTING)
Page 476 of 5267
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.
Istheresistancemorethan100kohms?
Ye s>>
Go To 4
No>>
Repair or replace the Engine harness shorted.
Perform POWERTRAIN VERIFICATION TEST VER - 1
(DIESEL). (Refer to 9 - ENGINE - DIAGNOSIS AND TEST-
ING)
4.HARNESS SHORTED (ECM SIDE)
Measure the resistance between the (K615) signal circuit and all other
circuits at the ECM harness connector.
Istheresistancemorethan100kohms?
Ye s>>
Go To 5
No>>
Repair or replace the ECM harness shorted.
Perform POWERTRAIN VERIFICATION TEST VER - 1
(DIESEL). (Refer to 9 - ENGINE - DIAGNOSIS AND TEST-
ING)
Page 477 of 5267

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.
Is the voltage between 4.5 and 5.5 volts?
Ye s>>
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.
Did the DTC P0073 set?
Ye s>>
Refer to the INTERMITTENT CONDITION Symptom (Diagnostic Procedure) (Referto9-ENGINE-
DIAGNOSIS AND TESTING).
No>>
Replace the ECM.
Perform POWERTRAIN VERIFICATION TEST VER - 1 (DIESEL). (Refer to 9 - ENGINE- DIAGNOSIS
AND TESTING)
7.(K668) 5-VOLT SUPPLY OPEN
Disconnect the ECM harness connectors.
Measure the voltage at the (K668) 5-volt supply circuit at the ECM har-
ness connector.
Is the voltage between 4.5 and 5.5 volts?
Ye s>>
Fix or repair the (K668) 5-volt supply circuit shorted to volt-
age.
Perform POWERTRAIN VERIFICATION TEST VER - 1
(DIESEL). (Refer to 9 - ENGINE - DIAGNOSIS AND TEST-
ING)
No>>
Replace the ECM.
Perform POWERTRAIN VERIFICATION TEST VER - 1
(DIESEL). (Refer to 9 - ENGINE - DIAGNOSIS AND TEST-
ING)
Page 478 of 5267
P0073-INLET AIR TEMP SENSOR VOLTAGE TOO HIGH
For a complete wiring diagramRefer to Section 8W.
Page 479 of 5267

When Monitored:
With ignition on and battery voltage greater than 10.4 volts.
Set Condition:
The circuit voltage to the ECM is above a calibrated threshold for a certainperiod of time.
Possible Causes
DTC RETURNS
INLET AIR TEMPERATURE SENSOR
(K615) SIGNAL CIRCUIT OPEN
(K690) RETURN CIRCUIT OPEN
(K615) SIGNAL CIRCUIT SHORTED
INTERMITTENT CONDITION
ECM
Always perform the Pre-Diagnostic Troubleshooting procedure before proceeding. (Refer to 9 - ENGINE -
DIAGNOSIS AND TESTING)
Diagnostic Test
1.DTC RETURNS
Turn the ignition on.
With the scan tool, erase DTCs.
With the scan tool, read DTCs.
With the scan tool, record all Freeze frame data.
Did the DTC return?
Ye s>>
Go To 2
No>>
Refer to the INTERMITTENT CONDITION Symptom (Diagnostic Procedure). (Refer to 9 - ENGINE -
DIAGNOSIS AND TESTING)
2.INLET AIR TEMPERATURE SENSOR
Turn the ignition off.
Disconnect the Inlet Air Temp sensor harness connector.
Check connectors - Clean/repair as necessary.
Measure the resistance of the Inlet Air temp sensor
Is the resistance between 300 and 90k ohms?
Ye s>>
Go To 3
No>>
Replace the Inlet air temperature sensor.
Perform POWERTRAIN VERIFICATION TEST VER - 1 (DIESEL). (Refer to 8 - ELECTRICAL/ELEC-
TRONIC CONTROL MODULES/ENGINE CONTROL MODULE - DIAGNOSIS AND TESTING).
Page 480 of 5267
3.RESISTANCE CHECK
Disconnect the ECM harness connector.
Check connectors - Clean/repair as necessary.
Reconnect the Inlet Air Temp sensor harness connector.
Measure the resistance between the (K615) inlet air temperature sensor
signal circuit and (K690) return circuit at the ECM connector.
Is the resistance between 300 and 90k ohms?
Ye s>>
Go To 6
No>>
Go To 4
4.(K615) INLET AIR TEMPERATURE SIGNAL CIRCUIT OPEN
Disconnect the inlet Air Temp sensor harness connector.
Measure the resistance of the (K615) inlet air temperature sensor signal
circuit between the sensor harness connector and the ECM harness
connector.
Is the resistance less than 10 Ohms?
Ye s>>
Go To 5
No>>
Repair or replace the harness.
Perform POWERTRAIN VERIFICATION TEST VER - 1
(DIESEL). (Refer to 8 - ELECTRICAL/ELECTRONIC CON-
TROL MODULES/ENGINE CONTROL MODULE - DIAG-
NOSIS AND TESTING)
Page 481 of 5267
5.(K690) RETURN CIRCUIT OPEN
Measure the resistance of the sensor (K690) return circuit between the
sensor harness connector and the ECM harness connector.
Is the resistance less than 10 Ohms?
Ye s>>
Go To 6
No>>
Repair or replace the harness.
Perform POWERTRAIN VERIFICATION TEST VER - 1
(DIESEL). (Refer to 8 - ELECTRICAL/ELECTRONIC CON-
TROL MODULES/ENGINE CONTROL MODULE - DIAG-
NOSIS AND TESTING)
6.(K615) SIGNAL CIRCUIT SHORTED
Check for a short circuit from the (K615) signal circuit to all other cir-
cuits at the ECM harness connector.
Istheresistancemorethan100kohms?
Ye s>>
Go To 7
No>>
Repair or replace the harness for a short to ground in the
signal circuit.
Perform POWERTRAIN VERIFICATION TEST VER - 1
(DIESEL). (Refer to 8 - ELECTRICAL/ELECTRONIC CON-
TROL MODULES/ENGINE CONTROL MODULE - DIAG-
NOSIS AND TESTING)