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
Diagnostic Fault Information
Typical Scan Tool Data
Circuit/System Description
The sensors listed below are integrated within the mass air flow/multifunction intake air sensor:
* IAT sensor 1
* IAT sensor 2
* Humidity sensor
* MAF sensor
* BARO pressure sensor
The intake air 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 engine control module (ECM) applies 5 V to the signal circuit. The humidity sensor and the IAT sensor 2 share the same circuit.
The sensors listed below share an ECM supplied 5 V reference circuit:
* IAT sensor 2
* Humidity sensor
* Barometric pressure (BARO) sensor
The sensors listed below share an ECM supplied low reference circuit:
* IAT sensor 1
* IAT sensor 2
* Humidity sensor
* Barometric pressure (BARO) sensor
Conditions for Running the DTCs
P11C2, P11C3, and P11C4
* DTC P1682 is not set.
* The ignition is ON.
* The Ignition voltage is at least 11 V.
* 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 detects that the humidity sensor signal is intermittent or has abruptly changed over a period of time greater than 5 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.
* 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.
Reference Information
Schematic Reference
Engine Controls Schematics [1][2]Electrical Diagrams
Connector End View Reference
Component Connector End Views Fuel Pump and Level Sensor Assembly
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
EN 38522 - Variable Signal Generator
For equivalent regional tools, refer to Special Tools Tools and Equipment.
Circuit/System Verification
1. Engine idling, 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 %.
2. 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 systems OFF. It may take up to 2 minutes for all vehicle systems to power down. Test for less than 5 ohms between the low reference circuit terminal 7 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 Engine Control Module.
3. Ignition ON, test for 4.8-5.2 V between the 5 V reference circuit terminal 2 and ground.
• If less than the specified range, test the circuit for an open/high resistance, or short to ground on the 5 V reference circuit. If the circuit tests normal, replace the K20 Engine Control Module.
• If greater than the specified range, test for a short to voltage on the 5 V reference circuit. If the circuit tests normal, replace the K20 Engine Control Module.
4. Test for 4.8-5.2 V between the humidity signal circuit terminal 1 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.
• 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 leads of the EN 38522 - Variable Signal Generator as follows:
* Red lead to the signal circuit terminal 1 at the harness connector
* Black lead to ground
* Battery voltage supply lead to B+
6. Set the EN 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 Replacement Service and Repair for Mass Air Flow/Multifunction Intake Air Sensor replacement.
* Control Module References Control Module References for Engine Control Module replacement, programming, and setup.