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Tahoe / Yukon Service Manual

DTC P0101

Engine Controls and Fuel - 3.0L LM2 Diesel | Diagnostic Information and Procedures | Document ID: 5507626 Diagnostic Instructions Perform the Diagnostic System Check prior to using this diagnostic procedure: Diagnostic System Check - Vehicle Review the description of Strategy Based Diagnosis: Strategy Based Diagnosis An overview of each diagnostic category can be found here: Diagnostic Procedure Instructions DTC Descriptor DTC P0101 Mass Airflow Sensor Performance Diagnostic Fault Information

Circuit Short to Ground Open/High Resistance Short to Voltage Signal Performanc
Ignition U060F, U1346 U060F, U1346 — —
Signal P0102, P1101 P0102 P0102* P0101, P0103
Serial Data U060F, U1346 U060F, U1346 U060F, U1346 —
Ground — P0102, U060F, U1346 — P0102
* Internal control module or component damage may occur if the circuit shorts to B+.

Typical Scan Tool Data Mass Airflow Sensor

Circuit Short to Ground Open Short to Voltage
Operating Conditions: Engine = Running At Idle Speed Parameter Normal Range: 2,000 to 3,000 Hz
Ignition 0 Hz 0 Hz —
Signal 0 Hz 0 Hz 0 Hz
Ground — 0 Hz —

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Circuit Description
Ignition Supplied from a fuse.
Signal The control module input circuit has an internal resistance connected to 5 V.
Ground Chassis Ground
Component Description
B75 Mass Airflow Sensor The assembly has several functions: The mass air flow sensor is a hot film type sensor that measures the mass of air (not the volume) entering the engine. The signal varies with engine load and is displayed by the scan tool in Hertz (Hz) and grams per second (g/s). The component houses the following sensors: – Barometric Pressure Sensor 2 – Intake Air Temperature Sensor – Intake Air Temperature Sensor 2 – Ambient Humidity
K20 Engine Control Module The control module contains a microprocessor used to process input data to control outputs. The control module controls a series of actuators to ensure optimal engine performance. The control module does this by reading values from a variety of sensors, interprets the data and adjusts the engine actuators accordingly.

Conditions for Running the DTC Condition 1 DTC P00C7, P0071–P0074, P0102, P0103, P0107, P0108, P0111–P0114, P0116–P0119, P0128, P0201, P0202, P0203, P0204, P020A, P020B, P020C, P020D, P0216, P02EE, P02EF, P02E8, P02E9, P02F0, P02F1, P0261, P0262, P0264, P0265, P0267, P0268, P0270, P0271, P0405, P0406, P049D, P0502, P0503, P062B, P062D, P0722, P0723, P111E, P122D, P124A, P124B, P1248, P1249, P126A, P2147, P2148, P2150, P2151, P2227, P2228, P2229, P2230, U060F = Not set Ambient Air Temperature = Warmer than −20°C (−4°F) Barometric Pressure = Greater than 69.5 kPa (10.1 PSI) Intake Air Flow Control Valve Position = Greater than 85% Exhaust Gas Recirculation Valve Position Sensor 1–2 = Less than 1% Engine Coolant Temperature = 40 to 130°C (104 to 266°F) Ignition and Start Signal = Greater than 11 V Intake Air Temperature Sensor = Warmer than −20°C (−4°F) Intake Manifold Pressure = 70 to 130 kPa (10.1 to 18.8 PSI) — Stable Frequency the DTC runs = Continuously — After the running conditions are met — For greater than 2 s Condition 2 DTC P00C7, P0071–P0074, P0102, P0103, P0107, P0108, P0111–P0114, P0116–P0119, P0128, P0201, P0202, P0203, P0204, P020A, P020B, P020C, P020D, P0216, P02EE, P02EF, P02E8, P02E9, P02F0, P02F1, P0261, P0262, P0264, P0265, P0267, P0268, P0270, P0271, P0405, P0406, P049D, P0502, P0503, P062B, P062D, P0722, P0723, P111E, P122D, P124A, P124B, P1248, P1249, P126A, P2147, P2148, P2150, P2151, P2227, P2228, P2229, P2230, U060F = Not set Ambient Air Temperature = Warmer than −20°C (−4°F) Barometric Pressure = Greater than 69.5 kPa (10.1 PSI) Intake Air Flow Control Valve Position = Greater than 85% Exhaust Gas Recirculation Valve Position Sensor 1–2 = Less than 1% — Greater than 0.3 s Engine Coolant Temperature = 40 to 130°C (104 to 266°F) Engine Speed = 550 to 1,000 RPM — Greater than 9 s Fuel Rate per Cylinder = 4 to 10 mm³ Ignition and Start Signal = Greater than 11 V Intake Air Temperature Sensor = Warmer than −20°C (−4°F) Intake Manifold Pressure = 70 to 130 kPa (10.1 to 18.8 PSI) — Stable Vehicle Speed = Less than 3 km/h (2 MPH) Frequency the DTC runs = Continuously — After the running conditions are met — For greater than 2 s Conditions for Setting the DTC Induction System Leak Indication ≠ 0.75:1 to 1.25:1 — For greater than 10 s Actions Taken When the DTC Sets DTCs listed in the DTC Descriptor category = Type A DTC Warning Message = Engine Power Is¦Reduced / Service Emission System / Service Exhaust Fluid System Reduced Engine Power = Active Conditions for Clearing the DTC DTCs listed in the DTC Descriptor category = Type A DTC Diagnostic Aids Inspect the sensing element for contamination and clean it if possible. If the sensing element cannot be cleaned » Replace the sensor. When the EGR valves are commanded to less than 1%, the ideal Induction System Leak Indication parameter is 1.0:1; the normal range is between 0.75:1 and 1.25:1. A scan tool Induction System Leak Indication parameter greater than 1.25:1, when the EGR valves are commanded to less than 1%, may indicate: – A leak after the turbocharger – An inaccurate MAP sensor – An inaccurate IAT sensor 3 – A skewed MAF sensor A scan tool Induction System Leak Indication parameter less than 0.75:1, when the EGR valves are commanded to less than 1%, may indicate: – A leak before the turbocharger – An inaccurate MAP sensor – An inaccurate IAT sensor 3 – A skewed MAF sensor – A leaking EGR valve, when it is commanded closed – A leaking positive crankcase valve (PCV) system Reference Information Schematic Reference Engine Controls Schematics Connector End View Reference Master Electrical Component List Electrical Information Reference Circuit Testing Connector Repairs Testing for Intermittent Conditions and Poor Connections Wiring Repairs DTC Type Reference Powertrain Diagnostic Trouble Code (DTC) Type Definitions Scan Tool Reference Control Module References Special Tools EL-38522 Variable Signal Generator Equivalent regional tools: Special Tools Circuit/System Verification

  1. Engine » Idling
  2. Verify DTC P0016, P007B–P007E, P00E9, P00EA–P00EC, P0096–P0099, P0102, P0103, P0106– P0108, P0111–P0114, P0116–P0119, P0128, P0201–P0204, P020A–P020D, P0216, P02E8, P02E9, P0261, P0262, P0264, P0265, P0268, P026A, P0270, P0271, P0405, P0406, P049D, P0502, P0503, P062B, P062D, P062F, P0722, P0723, P10D5–P10D8, P122D, P12B0–P12B2, P12AF, P1248, P1249, P2004, P2006, P2008–P2010, P201B, P201D, P20F8, P2147, P2148, P2150, P2151, P2227–P2230, U060F is not set. ⇒ If any of the DTCs are set Refer to: Diagnostic Trouble Code (DTC) List - Vehicle ⇓ If none of the DTCs are set
  3. Increase the engine speed slowly to 1,600 RPM and then back to idle.
  4. Perform the scan tool function: Review Stored Data
  5. Observe the scan tool parameter frame by frame with a scan tool: Mass Airflow Sensor Verify the scan tool parameter: Mass Airflow Sensor = The value should not spike or drop out. ⇒ If the value spikes or drops out Refer to: Circuit/System Testing ⇓ If the value does not spike or drop out
  6. Verify the scan tool parameter: Mass Airflow Sensor = The value should not spike or drop out. Perform the action while monitoring the parameter: Wiggle the harness and connector: B75 Mass Airflow Sensor Wiggle the harness and connector: K20 Engine Control Module ⇒ If the value spikes or drops out Repair as necessary » Wiring / Terminal(s) / Electrical Connector(s) ⇓ If the value does not spike or drop out
  7. Verify the scan tool parameter: Induction System Leak Indication = 0.75:1 to 1.25:1 — Stable ⇒ If not in the specified range 7.1. Ignition/Vehicle & All vehicle systems » Off 7.2. Verify the following conditions do not exist: B65 Intake Manifold Pressure and Air Temperature Sensor — Leaking @ O-Ring — Missing / Visible Damage B75 Mass Airflow Sensor — Contamination of the measuring element / Water intrusion / Leaking / Visible Damage Q14 Exhaust Gas Recirculation Valve — Stuck Open / Leaking Q22 Intake Manifold Tuning Solenoid Valve — Binding or Sticking Air Cleaner Element — Dirty / Restricted Charge Air Cooler – Leaking — Loose Clamps / Visible Damage – Restricted — Moisture / Ice Refer to: Component/System Leak Test Exhaust System — Loose / Missing components / Restricted / Visible Damage » Refer to: Symptoms - Engine Exhaust Intake Air Duct — Collapsed / Loose Clamps / Restricted / Visible Damage Intake Manifold — Cracked / Loose Clamps / Visible Damage Positive Crankcase Ventilation Oil Separator — Cracked / Leaking / Loose Clamps / Restricted ⇒ If a condition exists » Repair or replace as necessary ⇓ If in the specified range
  8. 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. Verify the DTC does not set. ⇒ If the DTC is set Repeat step 2 ⇓ If the DTC is not set
  9. All OK. Circuit/System Testing
  1. Disconnect the electrical connector: B75 Mass Airflow Sensor
  2. Install the special tool: EL-38522 Variable Signal Generator Red lead @ Signal circuit terminal 2 Black lead @ Ground Set the voltage to 5 V Set the frequency to 5 000 Hz Set the duty cycle to 50%
  3. Engine at Idle
  4. Verify the scan tool parameter: MAF Sensor = 4 950 to 5 050 Hz ⇒ If not between 4 950 and 5 050 Hz 5.1. Ignition/Vehicle » Off 5.2. Disconnect the appropriate electrical connector: K20 Engine Control Module 5.3. Test for less than 2 Ω between the test points: Signal circuit terminal 2 @ Component harness & The other end of the circuit @ Control module harness ⇒ If 2 Ω or greater » Repair the open/high resistance in the circuit. ⇒ If less than 2 Ω » Replace the component: K20 Engine Control Module ⇓ If between 4 950 and 5 050 Hz
  5. Replace the component: B75 Mass Airflow Sensor Repair Instructions Perform the Diagnostic Repair Verification after completing the repair: Diagnostic Repair Verification Mass Airflow Sensor with Intake Air Temperature Sensor Replacement For control module replacement, programming, and setup refer to: Control Module References Additional Procedures Barometric Pressure Sensor Reset — Perform only when the following component/system is replaced or serviced: K20 Engine Control Module — Replaced B75 Mass Airflow Sensor — Cleaned / Replaced
  1. Ignition » On / Vehicle » In Service Mode
  2. Verify that all scan tool Event Data parameters under the following data list displays No: Exhaust Gas Recirculation System Malfunction Warning Event Data ⇒ If not the specified state Operate the vehicle within the Conditions for Running the DTC for the DTC identified by the Event Data parameter displaying Yes. ⇓ If the specified state
  3. All OK.