P11C3
DTC P11C2-P11C4
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 Descriptors
DTC P11C2
- Intake Air Humidity Sensor Circuit Low Voltage
DTC P11C3
- Intake Air Humidity Sensor Circuit High Voltage
DTC P11C4
- Intake Air Humidity Sensor Circuit Erratic
Typical Scan Tool Data
Circuit/System Description
The humidity sensor measures the ambient humidity of the air in the sensor bore. The signal varies with intake air humidity and is displayed by the scan tool as duty cycle %. The ECM applies 5 V to the circuit. The signal circuit is shared by the humidity sensor and the intake air temperature (IAT) sensor 2. Ignition voltage and ground circuits are also supplied to the multifunction intake air sensor's internal circuits for these sensors:
* IAT sensor 2
* Humidity sensor
* MAF sensor
The multifunction intake air sensor houses the following:
* IAT sensor 1
* IAT sensor 2
* Humidity sensor
* MAF sensor
* BARO pressure sensor
Conditions for Running the DTCs
P11C2, P11C3, and P11C4
* The ignition is ON.
* The Ignition 1 voltage is at least 11 V for longer than 0.9 s.
* These DTCs run continuously within the enabling conditions.
Conditions for Setting the DTCs
P11C2
The ECM detects that the humidity sensor signal is less than or equal to 5 % for greater than 5 s.
P11C3
The ECM detects that the humidity sensor signal is greater than or equal to 95 % for greater than 5 s.
P11C4
The ECM monitors the IAT sensor signal every 0.1 s, to determine if the signal has changed more than 80 %. The DTC fails when the condition exists for longer than 4 s.
Action Taken When the DTC Sets
DTCs P11C2, P11C3, P11C4 are Type B DTCs.
Conditions for Clearing the MIL/DTC
DTCs P11C2, P11C3, P11C4 are Type B DTCs.
Diagnostic Aids
* The Intake Air Humidity Signal parameter displays the measured humidity within the air intake system and may differ from atmospheric humidity measured outside the air intake system.
* With the ignition ON, the engine OFF, if the engine is cold, a properly functioning humidity sensor will gradually increase the scan tool Intake Air Humidity Signal parameter. This is due to the heat that is generated by the multifunction intake air sensor heating elements.
* The humidity sensor and the IAT sensor 2 signals are sent to the ECM on the same circuit. If the Intake Air Humidity parameter displays the value: 0 % or 100 %, and there are also IAT Sensor 2 DTCs, check for a circuit problem.
* With the ignition ON, the engine OFF, if the engine is cold, a properly functioning IAT sensor 2 will gradually increase the scan tool IAT Sensor 2 parameter. This is due to the heat that is generated by the multifunction intake air sensor heating elements.
Reference Information
Schematic Reference
Engine Controls Schematics (LE9) [1][2]Electrical Diagrams
Connector End View Reference
Component Connector End Views Sunshade - Left (DH6)
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 Control Module References for scan tool information
Special Tools
J 38522 - Variable Speed Generator
For equivalent regional tools, refer to Special Tools (Diagnostic Tools) Tools and Equipment.
Circuit/System Verification
1. Ignition ON. Observe the scan tool IAT Sensor 1 and 2 parameters. The readings should be within 30°C (54°F) of each other.
2. Engine running, observe the scan tool Intake Air Humidity parameter. Depending on the current ambient humidity and temperature; engine bay conditions; and the vehicle operating conditions, the reading should be between 5 and 90 %.
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 B75C multifunction intake air sensor.
2. Ignition OFF, all vehicle systems OFF, test for less than 5 ohms between the ground circuit terminal 7 and ground.
• If greater than the specified range, test the ground circuit for an open/high resistance.
3. Ignition ON, verify that a test lamp illuminates between the ignition circuit terminal 5 and ground.
• If the test lamp does not illuminate, test the ignition circuit for a short to ground or an open/high resistance.
• If the circuit tests normal and the fuse is open, test all the components connected to the circuit and repair or replace as necessary.
4. Ignition ON, test for 4.8-5.2 V between the humidity signal circuit terminal 8 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 engine control module.
Note: If the signal circuit is shorted to a voltage the ECM or the sensor may be damaged.
• If greater than the specified range, test the signal circuit for a short to voltage. If the circuit tests normal, replace the K20 engine control module.
5. Ignition OFF, connect the red lead of the J 38522 - variable signal generator to the signal circuit terminal 8 at the harness connector. Connect the battery voltage supply to B+, and the black lead to ground.
6. Set the J 38522 - variable signal generator to the following specifications.
* Signal switch to 5 V
* Frequency switch to 250 Hz
* Duty Cycle switch to 50 % (Normal)
7. Ignition ON, observe the scan tool Intake Air Humidity parameter. The scan tool parameter should be between 45-55 %.
• If the parameter is not within the specified range, replace the K20 engine control module.
8. If all circuits test normal, test or replace the B75C multifunction intake air sensor.
Repair Instructions
Perform the Diagnostic Repair Verification Verification Tests after completing the repair.
* Mass Airflow Sensor with Intake Air Temperature Sensor Replacement Service and Repair for multifunction intake air sensor replacement.
* Control Module References Control Module References for engine control module replacement, programming, and setup.