Buick Regal: DTC P00F4-P00F6

Diagnostic Instructions

• Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure.
• Review Strategy Based Diagnosis for an overview of the diagnostic approach.
• Diagnostic Procedure Instructions provides an overview of each diagnostic category.

DTC Descriptors

DTC P00F4

Intake Air Humidity Sensor Circuit Low Voltage

DTC P00F5

Intake Air Humidity Sensor Circuit High Voltage

DTC P00F6

Intake Air Humidity Sensor Circuit Erratic

Diagnostic Fault Information

Intake Air Humidity

IAT Sensor 2

Typical Scan Tool Data

Intake Air Humidity

IAT Sensor 2

Circuit/System Description

The sensors listed below are integrated within the Multifunction Intake Air sensor:

• IAT sensor 1
• IAT sensor 2
• Humidity sensor
• MAF sensor
• BARO pressure sensor

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 humidity sensor and the intake air temperature (IAT) sensor 2 share the same signal circuit. The ECM applies 5 V to the circuit.

Ignition voltage and ground circuits are supplied to the multifunction intake air sensor's internal circuits for these sensors:

• IAT sensor 2
• Humidity sensor
• MAF sensor

Conditions for Running the DTCs

P00F4, P00F5, and P00F6

• DTC P1682 is not active.
• 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

P00F4

The ECM detects that the humidity sensor signal is less than or equal to 5 % for greater than 4 s.

P00F5

The ECM detects that the humidity sensor signal is greater than or equal to 95 % for greater than 4 s.

P00F6

The ECM monitors the humidity 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 P00F4, P00F5, and P00F6 are Type B DTCs - North America and Korea.
• DTCs P00F4, P00F5, and P00F6 are Type C DTCs - Except North America and Korea.

Conditions for Clearing the MIL/DTC

• DTCs P00F4, P00F5, and P00F6 are Type B DTCs - North America and Korea.
• DTCs P00F4, P00F5, and P00F6 are Type C DTCs - Except North America and Korea.

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 Wiring Schematics (LTG)

Connector End View Reference

Component Connector End View Index

Electrical Information Reference

• Circuit Testing
• Connector Repairs
• Testing for Intermittent Conditions and Poor Connections
• Wiring Repairs

Powertrain Component Views

Powertrain Component Views

DTC Type Reference

Powertrain Diagnostic Trouble Code (DTC) Type Definitions

Scan Tool Reference

Control Module References for scan tool information

Special Tools

EL-38522-A Variable Signal Generator

For equivalent regional tools, refer to Special Tools (diagnostic tools) and Special Tools (Mechanical Tools).

Circuit/System Verification

NOTE: To minimize the effects of residual engine heat and sensor internal heating elements, perform Steps 1 and 2 of this verification procedure only if the ignition has been OFF for 8 hours or more.

1. Ignition ON.

2. Verify the following scan tool parameters are within 25ºC (45ºF) of each other.

• Start-Up IAT Sensor 1
• Start-Up IAT Sensor 2
• Start-Up IAT Sensor 3; where equipped
• If not within 25ºC (45ºF)

Refer to Circuit/System Testing.

• Go to next step: If within 25ºC (45ºF)

3. Engine idling, verify the scan tool Intake Air Humidity parameter is between 5 and 90 %.

• If not between 5 and 90 %

Refer to Circuit/System Testing.

• Go to next step: If between 5 and 90 %

4. Operate the vehicle within the conditions for running the DTC. You may also operate the vehicle within the conditions that you observed from the freeze frame/failure records data.

5. Verify the DTC does not set.

• If the DTC sets

Refer to Circuit/System Testing.

• Go to next step: If the DTC does not set

6. All OK

Circuit/System Testing

NOTE: You must perform the Circuit/System Verification before proceeding with Circuit/System Testing.

1. Ignition OFF, disconnect the harness connector at the B75C Multifunction Intake Air sensor (Humidity Sensor).

2. Test for less than 5 Ω between the ground circuit terminal 7 and ground.

• If 5 Ω or greater

1. Ignition OFF, disconnect the harness connector at the K20 Engine Control Module.
2. Test for less than 2 Ω in the low reference circuit end to end.
   • If 2 Ω or greater, repair the open or high resistance in the circuit.
   • If less than 2 Ω replace the K20 Engine Control Module.

• Go to next step: If less than 5 Ω

3. Ignition ON, verify that a test lamp illuminates between the ignition circuit terminal 5 and ground.

• If the test lamp does not illuminate and the circuit fuse is good

1. Ignition OFF, remove the test lamp and remove the fuse for the ignition voltage circuit.
2. Test for less than 2 Ω in the ignition voltage circuit end to end.
   • If 2 Ω or greater, repair the open/high resistance in the circuit.
   • If less than 2 Ω, verify the fuse is not open and there is voltage at the fuse.

• If the test lamp does not illuminate and the circuit fuse is open

1. Ignition OFF, remove the test lamp and remove the fuse for the ignition voltage circuit.
2. Test for infinite resistance between the ignition voltage circuit and ground.
   • If less than infinite resistance, repair the short to ground on the circuit.
   • If infinite resistance, test all components connected to the ignition circuit, replace as necessary.

• Go to next step: If a test lamp illuminates

NOTE:

• The IAT 2 parameter and the Intake Air Humidity Sensor parameter share the same signal circuit.
• The intake air temperature sensor 2 signal circuit is pulled up with low current voltage within the controller. Normally, a voltage can be measured on the circuit with a DMM, but the current will not be high enough to illuminate a test lamp.

4. Ignition On/Vehicle in Service Mode, verify the scan tool Intake Air Humidity Sensor parameter is less than 1%.

• If 1% or greater

1. Vehicle OFF, disconnect the harness connector at the K20 Engine Control Module.
2. Test for infinite resistance between the IAT 2 signal circuit terminal 8 and ground.
   • If less than infinite resistance, repair the short to ground on the circuit.
   • If infinite resistance, replace the K20 Engine Control Module.

• Go to next step: If less than 1%

5. Vehicle OFF, install a 3 A fused jumper wire between the IAT 2 signal circuit terminal 8 and the low reference circuit terminal 3, Ignition On/Vehicle in Service Mode.

6. Verify the scan tool Intake Air Humidity Sensor parameter is greater than 99%.

• If 99% or less

NOTE: If the signal circuit is shorted to a voltage the engine control module or the sensor may be damaged.

1. Vehicle OFF, remove the jumper wire and disconnect the harness connector at the K20 Engine Control Module, Ignition On/Vehicle in Service Mode.
2. Test for less than 1 V between the IAT 2 signal circuit terminal 8 and ground.
   • If 1 V or greater, repair the short to voltage on the circuit.
   • Go to next step: If less than 1 V.
3. Vehicle OFF.
4. Test for less than 2 Ω in the signal circuit end to end.
   • If 2 Ω or greater, repair the open/high resistance in the circuit.
   • If less than 2 Ω, replace the K20 Engine Control Module.

• Go to next step: If greater than 99%

7. Test or replace the B75C Multifunction Intake Air sensor (IAT 2 Humidity Sensor).

Component Testing

Multifunction Intake Air Sensor

1. Test the Intake Air Humidity Sensor by varying the air humidity in the intake duct near the sensor, while observing the scan tool Intake Air Humidity Sensor parameter. The parameter should change and be within 5 - 95%.

• If not within the specified range

Replace the B75C Multifunction Intake Air Sensor.

• Go to next step: If within the specified range

2. All OK.

IAT 2 Circuit Testing with EL-38522-A

NOTE: In-correct diagnosis will result if Circuit/System Testing is not completed before performing the following test.

1. Perform the following test using a EL-38522-A Variable Signal Generator or equivalent, if available.

2. Vehicle Off, connect the leads of the EL-38522-A Variable Signal Generator as follows:

1. Red lead to the signal circuit terminal 8 at the harness connector
2. Black leads to ground
3. Battery voltage supply lead to B+

3. Set the EL-38522-A Variable Signal Generator to the following specifications.

• Signal switch to 5 V
• Duty Cycle switch to 50 % (Normal)
• Frequency switch to 250 Hz

4. Ignition On/Vehicle in Service Mode.

5. Verify the scan tool IAT Sensor 2 parameters listed below are within the ranges listed below:

• IAT Sensor 2 is between 248 - 252 Hz

NOTE: Changing the frequency should cause a warmer or colder IAT 2 temperature.

• IAT Sensor 2 is between 70 - 76ºC (160 - 166ºF)

NOTE: Increasing or decreasing the duty cycle should have an inverse affect on humidity.

• Intake Air Humidity Sensor is between 48 - 52%
• If a parameter is not within the specified range

1. Vehicle Off, disconnect the harness connector at the K20 Engine Control Module.
2. Test for less than 2 Ω in the signal circuit end to end.
   • If 2 Ω or greater, repair the open/high resistance in the circuit.
   • If less than 2 Ω, replace the K20 Engine Control Module.

• Go to next step: If all the parameters are within the specified range

6. All OK.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the repair.

• Mass Airflow Sensor with Intake Air Temperature Sensor Replacement for multifunction intake air sensor replacement
• Control Module References for Engine Control Module replacement, programming, and setup.

READ NEXT: