P0101

P0101-MASS AIR FLOW SENSOR "A" CIRCUIT PERFORMANCE





For a complete wiring diagram, refer to the Wiring Information.

Theory of Operation

The Mass Air Flow 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. This means that it's resistance drops when it's temperature drops. The drop in resistance allows more current to flow through it in order to maintain the programmed temperature. This current is changed to a frequency which is sent to the 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. This diagnostic has two parts, a key on monitor and a monitor that runs in operating conditions when the EGR valve is closed. The key on monitor diagnostic fails if the Mass Air Flow Sensor reads a non-zero value at key on, engine off. The engine running monitor compares an estimated charge air flow value to the Mass Air Flow sensor reading. This monitor only runs when the EGR valve is commanded closed. During this time the MAF sensor value should equal the charge air flow estimate. The PCM will light the MIL lamp if this diagnostic runs and fails in two consecutive drive cycles. The PCM will turn off the MIL lamp when the diagnostic runs and passes in four consecutive drive cycles.

- When Monitored:
Ignition on.

- Set Condition:
With the engine running and EGR flow equal to zero, the Mass Air Flow sensor value does not equal the charge air flow estimate.





Always perform the Pre-Diagnostic Troubleshooting procedure before proceeding. Pre-Diagnostic Troubleshooting 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. Intermittent Condition Test

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.
- Perform the POWERTRAIN VERIFICATION TEST - 6.7L. Powertrain Verification Test.

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.
- Perform the POWERTRAIN VERIFICATION TEST - 6.7L. Powertrain Verification Test.

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. Powertrain Verification Test.

5. CHECK FOR AN AIR LEAK IN THE INTAKE SYSTEM
1. Perform the INTAKE AIR SYSTEM PRESSURE TEST procedure. Intake Air System Pressure Test
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. Powertrain Verification Test.

No

- Replace the Mass Air Flow Sensor.
- Perform the POWERTRAIN VERIFICATION TEST - 6.7L. Powertrain Verification Test.