P0101 - Mass Air Flow Sensor "A" Circuit Performance
Theory of Operation
The Mass Air Flow (MAF) Sensor is a frequency based device. A constant voltage is applied to a heated wire. This wire is positioned in the air stream and is heated by the electrical current that the voltage produces. As air flows across it, it cools down. The heated wire or film is a Positive Temperature Coefficient (PTC) resistor, which means that the resistance of it drops when the temperature drops. The drop in resistance allows more
current to flow through it in order to maintain the programmed temperature. The current flow is changed to a frequency, which is sent to the Powertrain Control Module (PCM) and interpreted as air flow. Adjustments for air temperature and humidity are taken into consideration, since they also affect the temperature of the heated wire or film. The engine running monitor compares an estimated fresh air flow value to the MAF Sensor reading.
When Monitored and Set Conditions
When Monitored: This diagnostic runs continuously when the following conditions are met:
• With the Engine running.
Set Conditions:
• The Powertrain Control Module (PCM) has set the EGR flow equal to zero, but the Mass Air Flow sensor
value does not equal the charge air flow estimate.
Default Actions:
• The MIL is illuminated.
Possible Causes
TURBOCHARGER, EGR OR INTAKE AIR SYSTEM RELATED DTCS
MASS AIR FLOW (MAF) SENSOR
AIR FILTER
AIR INTAKE LEAK
Always perform the Pre-Diagnostic Troubleshooting procedure before proceeding. (Refer to 28 - DTCBased Diagnostics/MODULE, Powertrain Control (PCM) - Standard Procedure).
1. ACTIVE DTC
NOTE: If there are any other EGR, Turbocharger, or Intake system DTCs present, repair those DTCs before proceeding.
1. Turn the ignition on.
2. With the scan tool, record all Freeze frame data.
3. With the scan tool, erase DTCs.
4. Turn the ignition off for 75 seconds.
5. Start the engine attempt to duplicate the conditions that set the DTC.
6. With the scan tool, read DTCs.
Did the DTC reset?
Yes
• Go To 2
No
• Perform the INTERMITTENT CONDITION diagnostic procedure. (Refer to 28 - DTC-Based
Diagnostics/MODULE, Powertrain Control (PCM) - Standard Procedure).
2. CHECK THE MAF SENSOR
1. Start the engine. Warm the engine up to operating temperature and then let it idle for five minutes.
NOTE: This is how long it takes for the EGR Valve to close.
2. With the scan tool in Data Display, verify that the EGR Valve is at 0%.
3. With the scan tool, read the MAF Sensor value.
Does the Mass Air Flow Sensor read from 3.0 - 6.75 lb/min for an auto transmission, or 3.5 - 7.5 lb/min for a manual transmission?
Yes
• Go To 3
No
• Replace the Mass Air Flow Sensor in accordance with the Service Information.(Refer to 14 - Fuel System/Fuel Injection, Diesel/SENSOR, Mass Airflow (MAF) /Removal)
• Perform the POWERTRAIN VERIFICATION TEST - 6.7L. (Refer to 28 - DTC-Based Diagnostics/MODULE, Powertrain Control (PCM) - Standard Procedure).
3. CHECK THE AIR FILTER
1. Remove lid from air filter box.
2. Remove air filter and inspect for excessive debris or filter media damage.
3. Make sure the filter was installed properly.
Was the air filter damaged or full of debris?
Yes
• Replace the Air Filter in accordance with the Service Information..(Refer to 09 - Engine/Air Intake System/AIR CLEANER/Removal)
• Perform the POWERTRAIN VERIFICATION TEST - 6.7L. (Refer to 28 - DTC-Based Diagnostics/MODULE, Powertrain Control (PCM) - Standard Procedure).
No
• Go To 4
4. CHECK THE MAF SENSOR
1. Turn the Ignition off.
2. Remove MAF sensor from the air filter box.
Is it free from debris?
Yes
• Go To 5
No
• Clean the Mass Air Flow Sensor using low pressure air and reinstall, repair complete.
• Perform the POWERTRAIN VERIFICATION TEST - 6.7L. (Refer to 28 - DTC-Base Diagnostics/MODULE, Powertrain Control (PCM) - Standard Procedure).
5. CHECK FOR AN AIR LEAK IN THE INTAKE SYSTEM
1. Perform the INTAKE AIR SYSTEM PRESSURE TEST procedure. (Refer to 29 - Non-DTC Diagnostics/Drivability - Diesel - Diagnosis and Testing) .
2. Any leak between the air box to the intake manifold could cause this fault.
Were there any Intake Air System leaks?
Yes
• Repair the leak in the Intake Air System.
• Perform the POWERTRAIN VERIFICATION TEST - 6.7L. (Refer to 28 - DTC-Based Diagnostics/MODULE, Powertrain Control (PCM) - Standard Procedure
No
• Replace the Mass Air Flow Sensor in accordance with the Service Information.(Refer to 14 - Fuel
System/Fuel Injection, Diesel/SENSOR, Mass Airflow (MAF) /Removal)
• Perform the POWERTRAIN VERIFICATION TEST - 6.7L. (Refer to 28 - DTC-Based Diagnostics/MODULE, Powertrain Control (PCM) - Standard Procedure).