P0101

P0101-MASS AIR FLOW SENSOR "A" CIRCUIT PERFORMANCE





For a complete wiring diagram Refer to Diagrams/Electrical.

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 ECM 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 ECM will light the MIL lamp if this diagnostic runs and fails in two consecutive drive cycles. The ECM will turn off the MIL lamp when the diagnostic runs and passes in four consecutive drive cycles.

- When Monitored:
Ignition on.

- Set Condition:
Flow detected is greater than allowable threshold at key on/engine off. While running and EGR flow equals zero the Mass Air Flow sensor value does not equal the charge air flow estimate.







Always perform the Pre-Diagnostic Troubleshooting procedure before proceeding. Initial Inspection and Diagnostic Overview


Diagnostic Test


1. OTHER DTC'S
Ignition on, engine not running.
With the scan tool, read DTC's.
Are any other DTC'S present?

Yes


- Repair all other DTC's first.
- Perform POWERTRAIN VERIFICATION TEST - 6.7L. Powertrain Verification Test


No


- Go To 2



2. MAF SENSOR
With the scan tool in Sensors, read the Mass Air Flow sensor.
Does the Mass Air Flow sensor read 0 +/- 2lb/min?

Yes


- Go To 3


No


- Replace MAF sensor.
- Perform POWERTRAIN VERIFICATION TEST - 6.7L. Powertrain Verification Test



3. REPLACE AIR FILTER
Remove lid from air filter box.
Remove air filter and inspect for excessive debris or filter media damage.
Ensure the filter was installed properly.
Was the air filter damaged or full of debris?

Yes


- Replace air filter.
- Perform POWERTRAIN VERIFICATION TEST - 6.7L. Powertrain Verification Test


No


- Go To 4



4. MAF SENSOR DIRTY
Turn the Ignition off.
Remove MAF sensor from air box.
Is it free from debris?

Yes


- Go To 5


No


- Clean sensor using low pressure air and reinstall, repair complete.
- Perform POWERTRAIN VERIFICATION TEST - 6.7L. Powertrain Verification Test



5. AIR LEAK IN INTAKE SYSTEM
Check for an air intake leak.
Any leak between the air box to the intake manifold could cause this fault.
Were there any air intake leaks?

Yes


- Replace air filter.
- Perform POWERTRAIN VERIFICATION TEST - 6.7L. Powertrain Verification Test


No


- Refer to the INTERMITTENT CONDITION - DIESEL Symptom. Intermittent Condition