P0101
DTC P0101 (Heavy Duty L96)
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 Instructionsprovides an overview of each diagnostic category.
DTC Descriptors
DTC P0101
- Mass Air Flow (MAF) Sensor Performance
Diagnostic Fault Information
Typical Scan Tool Data
Circuit Description
The intake flow rationality diagnostic provides the within-range rationality check for the mass air flow (MAF), manifold absolute pressure (MAP), and the throttle position (TP) sensors. This is an explicit model-based diagnostic containing 4 separate models for the intake system.
* The throttle model describes the flow through the throttle body and is used to estimate the MAF through the throttle body as a function of barometric pressure (BARO), TP, intake air temperature (IAT), and estimated MAP. The information from this model is displayed on the scan tool as the MAF Performance Test parameter.
* The first intake manifold model describes the intake manifold and is used to estimate MAP as a function of the MAF into the manifold from the throttle body and the MAF out of the manifold caused by engine pumping. The flow into the manifold from the throttle uses the MAF estimate calculated from the above throttle model. The information from this model is displayed on the scan tool as the MAP Performance Test 1 parameter.
* The second intake manifold model is identical to the first intake manifold model except that the MAF sensor measurement is used instead of the throttle model estimate for the throttle air input. The information from this model is displayed on the scan tool as the MAP Performance Test 2 parameter.
* The fourth model is created from the combination and additional calculations of the throttle model and the first intake manifold model. The information from this model is displayed on the scan tool as the TP Performance Test parameter.
The estimates of MAF and MAP obtained from this system of models and calculations are then compared to the actual measured values from the MAF, MAP, and the TP sensors and to each other to determine the appropriate DTC to fail. The following table illustrates the possible failure combinations and the resulting DTC or DTCs.
Conditions for Running the DTC
* DTCs P0102, P0103, P0107, P0108, P0112, P0113, P0116, P0117, P0118, P0128, P0335, P0336 are not set.
* The engine speed is between 465-4,600 RPM.
* The IAT Sensor is between -20 and +100°C (-4 and +212°F).
* The ECT Sensor is between -7 and +125°C (+19 and +257°F).
* This DTC runs continuously within the enabling conditions.
Conditions for Setting the DTC
The engine control module (ECM) detects that the actual measured airflow from the MAF, MAP, and TP sensors is not within range of the calculated airflow that is derived from the system of models for more than 0.5 s.
Action Taken When the DTC Sets
DTC P0101 is aType B DTCs.
Conditions for Clearing the MIL/DTC
DTC P0101 is aType B DTCs.
Diagnostic Aids
* A steady or intermittent high resistance of 15 ohm or greater on the ignition voltage circuit will cause the MAF sensor signal to be increased by as much as 60 g/s. To pinpoint this condition perform a voltage drop test on the circuit.
* Any type of contamination on the MAF sensor heating elements will degrade the proper operation of the sensor. Certain types of contaminants act as a heat insulator, which will impair the response of the sensor to airflow changes. Water or snow can create the opposite effect, and cause the signal to increase rapidly.
* Depending on the current ambient temperature, and the vehicle operating conditions, a MAF sensor signal circuit that is shorted to the IAT signal circuit will increase or decrease the MAF sensor signal that is interpreted by the ECM. Additionally it may cause a rapid fluctuation in the IAT Sensor parameter.
* Compare the MAF Sensor parameter to a known good vehicle under various operating conditions. The MAF parameter should be within 2-4 g/s at idle and 20-40 g/s at the time of wide open throttle (WOT) 1-2 shift of the known good vehicle.
* A skewed or stuck engine coolant temperature (ECT) or IAT sensor will cause the calculated models to be inaccurate and may cause this DTC to run when it should not. Refer to Temperature Versus Resistance Temperature Versus Resistance.
* Certain aftermarket air filters may cause this DTC to set.
* Certain aftermarket air induction systems may cause this DTC to set.
* Modifications to the air induction system may cause this DTC to set.
Reference Information
Schematic Reference
Engine Controls Schematics (except L96) [1][2]Electrical DiagramsEngine Controls Schematics (L96) [1][2]Electrical Diagrams
Connector End View Reference
Component Connector End Views 1-2 Shift Solenoid (SS) Valve (M30)
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 Referencesfor scan tool information
Special Tools
J 38522 Variable Speed Generator
Circuit/System Verification
1. Ignition ON, observe the DTC information with a scan tool. Verify that DTC P0697 is not set.
• If aDTCs is set, refer to Diagnostic Trouble Code (DTC) List - Vehicle Diagnostic Trouble Code (DTC) List - Vehicle for DTC P0697 for further diagnosis.
2. Engine idling, observe the scan tool MAF Sensor parameter. The reading should be between 2,000-3,900 Hz depending on the ECT.
3. A WOT acceleration from a stop should cause the MAF Sensor parameter on the scan tool to increase rapidly. This increase should be from 4-9 g/s at idle to greater than 180 g/s at the time of the 1-2 shift.
4. Ignition ON, observe the scan tool MAP Sensor pressure parameter and compare to the Altitude Versus Barometric Pressure Altitude Versus Barometric Pressure table. The MAP sensor reading should be within the specified range.
• If the MAP sensor pressure is not within the specified range, refer to Diagnostic Trouble Code (DTC) List - Vehicle Diagnostic Trouble Code (DTC) List - Vehicle for DTC P0106 for further diagnosis.
5. Operate the vehicle within the Conditions for Running the DTC to verify 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. Verify the following conditions do not exist:
* A dirty or deteriorating air filter element
* A leaking, loose, or cracked PCV pipe or seal
* A restricted or collapsed air intake duct
* A misaligned or damaged air intake duct
* Any objects blocking the air inlet probe of the MAF/IAT sensor
* Any contamination or debris on the sensing elements in the probe of the MAF/IAT sensor
* A cracked or damaged MAF sensor housing
* Any water intrusion in the induction system
* Any snow or ice build-up at the air cleaner, MAF or MAP sensors in cold climates
* Any vacuum leak
* A MAP sensor seal that is leaking, missing, or damaged
* An Intake manifold resonator with a leaking seal, or a cracked or broken housing
* Verify restrictions do not exist in the exhaust system. Refer to Restricted Exhaust Restricted Exhaust.
• If you find any of the above conditions, repair as necessary.
2. Ignition OFF, disconnect the harness connector at the MAF/IAT sensor.
3. Ignition OFF and all vehicle systems OFF. It may take up to 2 minutes for all vehicle systems to power down. Test for less than 5 ohm between the ground circuit terminal E and ground.
• If greater than the specified range, test the ground circuit for an open/high resistance.
4. Ignition ON, verify that a test lamp illuminates between the ignition circuit terminal D and ground.
• If the test lamp does not illuminate, test the ignition circuit for a short to ground or an open/high resistance.
5. Ignition ON, test for 4.8-5.2 V between the MAF signal circuit terminal C and ground.
• If less than the specified range, test the MAF signal circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the ECM.
• If greater than the specified range, test the MAF signal circuit for a short to voltage. If the circuit tests normal, replace the ECM.
6. Ignition OFF, connect the red lead of the J 38522 to the MAF signal circuit terminal C at the MAF/IAT sensor harness connector. Connect the battery voltage supply to B+, and the black lead to ground.
7. Set the J 38522 Signal switch to 5 V, the Frequency switch to 5K, and the Duty Cycle switch to Normal.
8. Engine idling, observe the scan tool MAF Sensor parameter. The scan tool MAF Sensor parameter should be between 4,950-5,050 Hz.
• If not within the specified range, replace the ECM.
9. If all circuits test normal, test or replace the MAF/IAT sensor.
Repair Instructions
Perform the Diagnostic Repair Verification Verification Tests after completing the diagnostic procedure.
* Mass Airflow Sensor with Intake Air Temperature Sensor Replacement Service and Repair
* Control Module References Control Module Referencesfor ECM replacement, setup and programming