P112B
DTC P112B
Diagnostic Instructions
* Perform the Diagnostic System Check - Vehicle Diagnostic System Check - Vehicle prior to using this diagnostic procedure.
* Review Strategy Based Diagnosis Strategy Based Diagnosis for an overview of the diagnostic approach.
* Diagnostic Procedure Instructions Diagnostic Procedure Instructions provides an overview of each diagnostic category.
DTC Descriptor
DTC P112B
-
Intake Air Temperature (IAT) Sensor 3 Performance
Diagnostic Fault Information
Typical Scan Tool Data
Circuit/System Description
The intake air temperature (IAT) sensor 3 is a variable resistor that measures the temperature of the air in the sensor bore located before the throttle body. The IAT sensor 3 is integrated with the throttle inlet absolute pressure sensor. The engine control module (ECM) supplies 5 V to the IAT sensor 3 signal circuit and a ground for the IAT sensor 3 low reference circuit. The signal varies with inlet air temperature at the throttle body and is displayed by the scan tool as °C (°F).
Conditions for Running the DTC
P112B
* DTCs P0097, P0098, P0112, P0113, P0117, P0118, P0119, P112C, or P112D are not set.
* The vehicle has been OFF at least 8 hours.
* Ignition 1 voltage is at least 11 V.
* These DTCs run once per ignition cycle when the enabling conditions are met.
Conditions for Setting the DTC
P112B-Condition 1
* The ECM determines the absolute difference between IAT sensor 1 start-up temperature and the IAT sensor 2 start-up temperature is less or equal to 30°C (54°F).
AND
* The ECM determines the absolute difference between IAT sensor 3 start-up temperature and the IAT sensor 1 start-up temperature is greater than 25°C (77°F).
AND
* The ECM determines the absolute difference between IAT sensor 3 start-up temperature and the IAT sensor 2 start-up temperature is greater than 25°C (77°F).
AND
P112B-Condition 2
* The ECM determines the IAT sensor 1 start-up temperature is between the IAT sensor 3 start-up temperature and the IAT sensor 2 start-up temperature
AND
* The ECM determines the absolute difference between IAT sensor 3 start-up temperature and the IAT sensor 2 start-up temperature is greater than 25°C (77°F).
AND
* The absolute difference between IAT sensor 3 start-up temperature and the IAT sensor 1 start-up temperature is greater than the absolute difference between IAT sensor 2 start-up temperature and the IAT sensor 1 start-up temperature.
P112B-Condition 3
* The ECM determines the IAT sensor 2 start-up temperature is between the IAT sensor 3 start-up temperature and the IAT sensor 1 start-up temperature
AND
* The ECM determines the absolute difference between IAT sensor 3 start-up temperature and the IAT sensor 1 start-up temperature is greater than 25°C (77°F).
AND
* The absolute difference between IAT sensor 3 start-up temperature and the IAT sensor 2 start-up temperature is greater than the absolute difference between IAT sensor 2 start-up temperature and the IAT sensor 1 start-up temperature.
Action Taken When the DTC Sets
DTC P112B is a Type B DTC.
Conditions for Clearing the DTCs
DTC P112B is a Type B DTC.
Diagnostic Aids
* An IAT sensor 3 that is skewed, due to more resistance than is normal, can widen the spread between the 3 sensors and cause this DTC to set. Measure and record the resistance of the IAT sensor 3 at various ambient temperatures, and then compare those measurements to the Temperature vs. Resistance Table. Refer to Temperature Versus Resistance - Intake Air Temperature Sensor (Hitachi Sensor) Temperature Versus Resistance - Intake Air Temperature Sensor (Hitachi Sensor).
* A slight to moderate resistance in the IAT sensor 3 signal circuit or low reference circuit will increase the range between these sensors. This condition results in a greater voltage on the IAT sensor 3 signal circuit, which is interpreted by the ECM as a colder IAT sensor 3.
* Inspect the intake air sensor 3 terminals for corrosion.
Reference Information
Schematic Reference
Engine Controls Schematics [1][2]Electrical Diagrams
Connector End View Reference
Component Connector End Views Connector End Views By Name
Electrical Information Reference
* Circuit Testing Circuit Testing
* Connector Repairs Connector Repairs
* Testing for Intermittent Conditions and Poor Connections Testing for Intermittent Conditions and Poor Connections
* Wiring Repairs Wiring Repairs
DTC Type Reference
Powertrain Diagnostic Trouble Code (DTC) Type Definitions Powertrain Diagnostic Trouble Code (DTC) Type Definitions
Scan Tool Reference
Control Module References Programming and Relearning for scan tool information
Special Tools
* J 38522
* For equivalent regional tools, refer to Special Tools (Diagnostic Tools) Special Tools (Diagnostic Tools).
Circuit/System Verification
Note:
Perform Step 1 of this verification procedure only if the ignition has been OFF for 8 hours or more.
1. Ignition ON, observe the following scan tool parameters. The readings should be within 30°C (54°F) of each other.
* IAT Sensor 3
* Start-Up IAT Sensor 1
* IAT Sensor 2
2. Engine running, observe the scan tool IAT Sensor 1, IAT Sensor 2. and IAT Sensor 3 parameters. Depending on the current ambient temperature and the vehicle operating conditions, the readings should be between -38 and +149°C (-36 and +300°F).
3. Operate the vehicle within the conditions for running the DTC to verify that the DTC does not reset. You may also operate the vehicle within the conditions that you observed from the freeze frame/failure records data.
Circuit/System Testing
1. Ignition OFF, disconnect the harness connector at the B111B turbocharger boost/intake air temperature sensor.
2. Ignition OFF, all systems OFF. It may take up to for 2 minutes for all vehicle systems to power down. Test for less than 5 ohms between the low reference circuit terminal 1 and ground.
• If greater than the specified range, test the low reference circuit for an open/high resistance. If the circuit tests normal, replace the K20 ECM.
3. Ignition ON, verify the scan tool IAT Sensor 3 parameter is colder than -39°C (-38°F).
• If warmer than the specified range, test the signal circuit for a short to ground. If the circuit tests normal, replace the K20 ECM.
Note:
If the fuse in the jumper wire opens, the signal circuit is shorted to a voltage the ECM or the sensor may be damaged.
4. Install a 3 A fused jumper wire between the signal circuit terminal 2 and ground. Verify the scan tool IAT Sensor 3 parameter is warmer than 149°C (300°F).
• If colder than the specified range, test the signal circuit for a short to voltage or an open/high resistance. If the circuit tests normal, replace the K20 ECM.
5. Ignition ON, test for 4.8-5.2 V between the IAT sensor 3 signal circuit terminal 2 and ground.
• If less than the specified range, test the signal circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the K20 ECM.
6. If all circuits test normal, test or replace the B111B turbocharger boost/intake air temperature sensor.
Component Testing
1. Ignition OFF, disconnect the harness connector at the B111B turbocharger boost/intake air temperature sensor.
Note:
A thermometer can be used to test the sensor off the vehicle.
2. Test the IAT sensor 3 by varying the sensor temperature while monitoring the sensor resistance. Compare the readings with the Temperature Versus Resistance - Intake Air Temperature Sensor (Hitachi Sensor) Temperature Versus Resistance - Intake Air Temperature Sensor (Hitachi Sensor) table. The resistance values should be in range of the table values.
• If not within the specified range, replace the B111B turbocharger boost/intake air temperature sensor.
Repair Instructions
Perform the Diagnostic Repair Verification Verification Tests after completing the repair.
* Intake Air Pressure and Temperature Sensor Replacement Intake Air Pressure and Temperature Sensor Replacement for turbocharger boost/intake air temperature sensor.
* Control Module References Programming and Relearning for engine control module replacement, programming, and setup.