Intake Air Temperature (IAT) Sensor

1997 PCED OBDII-Diesel

SECTION 5C: Pinpoint Tests

C: Intake Air Temperature (IAT) Sensor

C: Introduction

C1 DIAGNOSTIC TROUBLE CODE (DTC) P0113

DTC P0113 (IAT) indicates that the corresponding sensor signal circuit is out of range high.
Possible causes:

open in harness
worn or damaged connection
worn or damaged sensor
damaged PCM

NGS Tester installed.
Key on/engine off.
Access IATV PID (voltage).

Is voltage reading 4.95v or above?

Yes	No
GO to C2.	GO to C8.

C2 INDUCE OPPOSITE FAILURE

Disconnect IAT sensor connector.
Jumper signal circuit Pin 2 on the IAT sensor connector to battery ground.

Does voltage reading on NGS Tester read 0v?

Yes	No
GO to C3.	GO to C4.

C3 CHECK SIGNAL RETURN

Key off.
Measure resistance between signal return Pin 1 on the IAT sensor connector and ground.

Is resistance less than 5 ohms?

Yes	No
REPLACE IAT sensor. CLEAR DTCs and RETEST.	REPAIR open in Signal Return Circuit 359 (GY/R). CLEAR DTCs and RETEST.

C4 CHECK CONTINUITY OF SENSOR SIGNAL AND SIG RTN CIRCUITS

Key off.
Suspect temperature sensor disconnected.
Disconnect PCM. Inspect for damaged or pushed-out pins, corrosion and loose wires. Service as necessary.
Install breakout box. Leave PCM disconnected.
Measure resistance between sensor signal circuit at the temperature sensor connector Pin 2 and Test Pin 39 (IAT) at the breakout box.

Is resistance less than 5 ohms?

Yes	No
Circuits OK. REPLACE PCM. REMOVE breakout box. Clear DTCs and RETEST.	SERVICE open in Circuit 743 (G/Y). CLEAR DTCs and RETEST.

C5 DIAGNOSTIC TROUBLE CODE (DTC) P0112

DTC P0112 (IAT) indicates that the corresponding sensor signal circuit is out of range low.
Possible causes:

grounded circuit in harness
worn or damaged sensor
damaged PCM
worn or damaged connection

NGS Tester installed.
Key on/engine off.
Access IATV PID (voltage).

Is voltage reading 0.13v or below?

Yes	No
GO to C6.	GO to C8.

C6 INDUCE FAILURE

Disconnect IAT sensor connector.

Does reading go to 4.59v or above?

Yes	No
REPLACE IAT sensor. CLEAR DTCs and RETEST.	GO to C7.

C7 CHECK TEMPERATURE SENSOR SIGNAL CIRCUIT FOR SHORT TO GROUND

Key off.
Suspect temperature sensor disconnected.
Disconnect PCM. Inspect for damaged or pushed-out pins, corrosion and loose wires. Service as necessary.
Install breakout box.
Disconnect PCM.
Measure resistance between Test Pin 39 (IAT) and Test Pins 51, 76, 77, 91 and 103.

Is each resistance greater than 10,000 ohms?

Yes	No
Circuits OK. REPLACE PCM. REMOVE breakout box. CLEAR DTCs and RETEST.	SERVICE short to ground Circuit 743 (G/Y). DISCONNECT breakout box. CLEAR DTCs and RETEST.

C8 CONTINUOUS MEMORY DIAGNOSTIC TROUBLE CODE (DTC) P0113 OR P0112: CHECK SENSOR

Continuous Memory DTC P0113 indicates that the sensor signal circuit was out of range high. The DTC was generated under normal driving conditions.
Continuous Memory DTC P0112 indicates that the sensor signal circuit was out of range low. The DTC was generated under normal driving conditions.
Possible causes:

worn or damaged sensor
open circuit in harness
grounded circuit in harness
damaged PCM

NGS Tester installed.
Key on/engine off.
Access IATV PID (voltage).
Tap on sensor while observing NGS Tester reading.

Does voltage reading fluctuate?

Yes	No
INSPECT for damaged or pushed-out pins. If OK, REPLACE IAT sensor. CLEAR DTCs and RETEST.	GO to C9.

C9 CHECK EEC VEHICLE HARNESS

Observe IAT value on NGS Tester while performing the following:

Grasp the vehicle harness close to the sensor connector.
Wiggle and shake vehicle harness while working toward the PCM.

Does valve fluctuate?

Yes	No
REPAIR circuits as required.	GO to C10.

C10 CHECK PCM AND VEHICLE HARNESS CONNECTORS

Key off.
Disconnect PCM. Disconnect sensor connector. Inspect for damage, loose or pushed-out pins, loose or poorly crimped wires.

Are connectors and terminals OK?

Yes	No
Unable to duplicate and/or identify concern at this time. CLEAR DTCs and RETEST.	SERVICE as necessary. CLEAR Continuous Memory codes and RETEST.