GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 GMC_Truck 🢒 2001 🢒 Yukon - 4WD 🢒 Engine 🢒 Engine Controls - 4.8L, 5.3L, and 6.0L 🢒 DTC P0101

Circuit Description

The mass air flow (MAF) sensor is an air flow meter that measures the amount of air entering the engine. The powertrain control module (PCM) uses the MAF sensor frequency signal in order to provide the correct fuel delivery for a wide range of engine speeds and loads. A small quantity of air entering the engine indicates a deceleration or idle. A large quantity of air entering the engine indicates an acceleration or a high load situation. The MAF sensor has an ignition 1 voltage circuit, a ground circuit, and a signal circuit. The PCM applies a voltage to the sensor on the signal circuit. The sensor uses the voltage in order to produce a frequency based on the inlet air flow through the sensor bore. The PCM uses the manifold absolute pressure (MAP), the intake air temperature (IAT), and the engine RPM in order to calculate a predicted MAF value. The PCM compares the actual MAF sensor frequency signal to the predicted MAF value in order to determine if the signal is stuck based on a lack of variation, or is too low or too high for a given operating condition. Diagnostic trouble code (DTC) P0101 will set if the actual MAF sensor frequency signal is not within a predetermined range of the calculated MAF value.

Conditions for Running the DTC
    • DTCs P0102, P0103, P0106, P0107, P0108, P0112, P0113, P0121, P0122, P0123, P1111, P1112, P1120, P1121, P1122, P1220, or P1221 are not set.
    • The engine is running.
    • The ignition 1 signal is between 11 and 18 volts.
    • The throttle position (TP) sensor angle is steady within a range of 5 percent or less.
    • The TP sensor angle is less than 95 percent.
    • The manifold absolute pressure (MAP) sensor is less than 80 kPa.
    • The MAP sensor is steady within a range of 3 kPa.
    • The above conditions exist for at least 2 seconds.

Conditions for Setting the DTC
    • The actual MAF sensor frequency signal is not within a predetermined range of the calculated MAF value
    • The above condition exists for 8 seconds.

Action Taken When the DTC Sets
    • The control module illuminates the malfunction indicator lamp (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails.
    • The control module records the operating conditions at the time the diagnostic fails. The first time the diagnostic fails, the control module stores this information in the Failure Records. If the diagnostic reports a failure on the second consecutive ignition cycle, the control module records the operating conditions at the time of the failure. The control module writes the operating conditions to the Freeze Frame and updates the Failure Records.

Conditions for Clearing the MIL/DTC
    • The control module turns OFF the malfunction indicator lamp (MIL) after 3 consecutive ignition cycles that the diagnostic runs and does not fail.
    • A current DTC, Last Test Failed, clears when the diagnostic runs and passes.
    • A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic.
    • Clear the MIL and the DTC with a scan tool.

Diagnostic Aids

Inspect for the following conditions:

    • A misrouted harness--Inspect the MAF sensor harness in order to ensure that the harness is not routed too closely to the following components:
       - Any secondary ignition wires or coils
       - Any solenoids
       - Any relays
       - Any motors
    • The throttle plate sticking, or excessive deposits on the throttle plate, or in the throttle bore.
    • Any unmetered air entering the engine may cause this DTC to set. Verify that the oil dipstick is fully seated and the oil fill cap is secure.
    • A wide open throttle (WOT) acceleration from a stop should cause the MAF value displayed on a scan tool to increase from about 4-7 gm/s at idle to 100 gm/s or more, at the time of the 1-2 shift. If not, inspect for a restriction.

If there is an intermittent, refer to Intermittent Conditions .

Test Description

The numbers below refer to the step numbers on the diagnostic table.

  1. Diagnose any MAF, MAP, TP or system voltage DTCs before using this table. If a misfire condition exists or a rough running condition is observed with or without DTC P0300 set, proceed to DTC P0300 first.

    2.

  2. Any unmetered air entering the engine may cause this DTC to set. This step eliminates any conditions which can cause a DTC to set with a normally operating MAF sensor.

    3.

  3. This step verifies the signal circuit from the MAF sensor electrical connector to the PCM. A voltage reading of less than 4 volts or more than 6 volts indicates a malfunction in the wiring or a faulty connection.

Step

Action

Values

Yes

No

Schematic Reference: Engine Controls Schematics

1

Did you perform the Diagnostic System Check-Engine Controls?

--

Go to Step 2

Go to Diagnostic System Check - Engine Controls

2

  1. Install a scan tool.
  2. Start the engine.
  3. Monitor the Diagnostic Trouble Code (DTC) Information using the scan tool.

Does the scan tool display any other DTCs set?

--

Go to Diagnostic Trouble Code (DTC) List

Go to Step 3

3
  1. Observe and record the Freeze Frame/Failure Records for this DTC.
  2. Turn OFF the ignition for 30 seconds.
  3. Start the engine.
  4. In order to operate the vehicle under the conditions which set the DTC, use the following information:
    5. • The data in the Freeze Frame/Failure Records
    • The parameters listed in the Conditions for Running in the DTC

Does the DTC fail this ignition?

--

Go to Step 4

Go to Diagnostic Aids

4
  1. Let the engine idle at the normal operating temperature.
  2. With a scan tool observe the MAP sensor voltage.

Is the MAP sensor voltage within the specified range?

0.8 - 4 V

Go to Step 5

Go to DTC P0106

5

  1. Turn OFF the ignition.
  2. Inspect for the following conditions:
    3. • Objects blocking the MAF sensor air inlet screen
    • A plugged intake air duct or a dirty air filter element
  3. Inspect for vacuum leaks in the following components:
    4. • The intake manifold
    • The throttle body
    • The EGR valve flange and pipe
    • The MAF sensor seal
    • The MAP sensor seal
    • The EVAP canister purge valve seal
    • The fuel meter body seal
    • The crankcase ventilation system.
    • The brake booster system
    • The air induction system

Did you find and correct the condition?

--

Go to Step 23

Go to Step 6

6
  1. Turn OFF the ignition.
  2. Remove the MAP sensor from the engine vacuum source, with the electrical harness connected. Refer to Manifold Absolute Pressure Sensor Replacement .
  3. Connect a hand-operated vacuum pump to the MAP sensor.
  4. Turn ON the ignition, leaving the engine OFF.
  5. With a scan tool observe or record the MAP sensor kPa parameter display as you SLOWLY apply vacuum 1 inch Hg at a time up to 20 inches Hg as indicated on the pump gauge. Each 1 inch of vacuum applied should result in a 3 to 4 kPa drop in the MAP sensor value on the scan tool. The value should change smoothly with each 1 inch increase in vacuum.

Does the MAP sensor value change smoothly through the entire range of the test?

--

Go to Step 7

Go to DTC P0106

7

Apply 20 inches Hg vacuum to the MAP sensor.

Is the MAP sensor reading equal to or less than the specified value?

34 kPa

Go to Step 8

Go to DTC P0106

8

Disconnect the vacuum source from the MAP sensor.

Does the MAP sensor reading return to the original value that was observed in Step 6?

--

Go to Step 9

Go to DTC P0106

9

Important: If the vehicle is equipped with electronic throttle control, proceed to the next step.

With a scan tool, observe the TP sensor angle parameter.

Does the scan tool display the specified value?

0%

Go to Step 10

Go to DTC P0121

10

  1. Turn OFF the ignition.
  2. Disconnect the MAF sensor harness connector.
  3. Turn ON the ignition, leaving the engine OFF.
  4. Measure the voltage from the signal circuit of the MAF sensor to a good ground. Refer to Circuit Testing in Wiring Systems.

Is the voltage near the specified value?

5.0 V

Go to Step 11

Go to Step 12

11

Connect a test lamp between the ignition 1 voltage circuit of the MAF sensor and the ground circuit of the MAF sensor. Refer to Circuit Testing in Wiring Systems.

Does the test lamp illuminate?

--

Go to Step 19

Go to Step 14

12

Is the voltage less than the specified value?

4.5 V

Go to Step 15

Go to Step 13

13

Important: Disconnecting the PCM connectors may eliminate the short to voltage if the signal circuit is shorted to another PCM circuit.

  1. Turn OFF the ignition.
  2. Disconnect the PCM. Refer to Powertrain Control Module Replacement .
  3. Turn ON the ignition, leaving the engine OFF.
  4. Measure the voltage from the signal circuit of the MAF sensor to a good ground.

Is the voltage at the specified value?

0.0 V

Go to Step 20

Go to Step 18

14

Connect a test lamp between the ignition 1 voltage circuit of the MAF sensor and a good ground. Refer to Circuit Testing in Wiring Systems.

Does the test lamp illuminate?

--

Go to Step 16

Go to Step 17

15
  1. Turn OFF the ignition.
  2. Disconnect the PCM. Refer to Powertrain Control Module Replacement

Test the signal circuit between the PCM and the MAF sensor for the following conditions:

    • A high resistance or an open
    • A short to ground
    • A short to the ground circuit of the MAF sensor

Refer to Circuit Testing and to Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 23

Go to Step 20

16

Repair the high resistance or an open in the ground circuit of the MAF sensor. Refer to Wiring Repairs in Wiring Systems.

Did you complete the repair?

--

Go to Step 23

--

17

  1. Repair the short to ground or an open in the ignition 1 voltage circuit of the MAF sensor. Refer to Wiring Repairs in Wiring Systems.
  2. Replace the fuse if necessary.

Did you complete the repair?

--

Go to Step 23

Go to Step 21

18

Repair the short to voltage in the signal circuit of the MAF sensor. Refer to Wiring Repairs in Wiring Systems.

Did you complete the repair?

--

Go to Step 23

--

19

Inspect for faulty connections at the harness connector of the MAF sensor. Refer to Testing for Intermittent Conditions and Poor Connections and to Connector Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 23

Go to Step 21

20

Inspect for faulty connections at the harness connector of the PCM. Refer to Testing for Intermittent Conditions and Poor Connections and to Connector Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 23

Go to Step 22

21

Replace the MAF/IAT sensor. Refer to Mass Airflow Sensor/Intake Air Temperature Sensor Replacement .

Did you complete the replacement?

--

Go to Step  23

--

22

Replace the PCM. Refer to Powertrain Control Module Replacement .

Did you complete the replacement?

--

Go to Step 23

--

23

  1. Use the scan tool in order to clear the DTCs.
  2. Turn OFF the ignition for 30 seconds.
  3. Start the engine.
  4. Operate the vehicle within the Conditions for Running the DTC.

Does the DTC run, and pass?

--

Go to Step 24

Go to Step 2

24

With a scan tool, observe the stored information, Capture Info.

Does the scan tool display any DTCs that you have not diagnosed?

--

Go to Diagnostic Trouble Code (DTC) List

System OK