GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 GMC_Truck 🢒 2002 🢒 GMC C Sierra - 2WD 🢒 DTC 🢒 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 engine control module (ECM) uses the MAF sensor voltage signal in order to provide the correct fuel delivery for a reduction in emissions. The ECM uses the MAF sensor signal in order to control fuel delivery until a calibrated amount of engine air flow is attained. The MAF sensor has an ignition 1 voltage circuit, a signal circuit and a low reference circuit. The MAF sensor produces an output voltage based on inlet air flow through the air induction system. This output voltage will display on the scan tool as a grams per second (g/s) value. The ECM will calculate a predicted MAF value. The ECM compares the actual MAF sensor voltage signal to the predicted MAF value. This comparison will determine if the signal is stuck, or is too low or too high for a given operating condition. DTC P0101 will set if the actual MAF sensor voltage signal is not within a predetermined range of the calculated MAF value.

Conditions for Running the DTC
    • DTC P0102, P0103, P0106, P0107, P0108, P0112, P0113, P0234, P0236, P0237, P0238, P0335, P0336, or P1345 are not set.
    • The ignition 1 signal is between 9-18 volts.
    • The engine speed is less than 2,500 RPM.
    • The engine speed is steady within a range of 50 RPM.
    • The accelerator pedal position (APP) indicated angle is less than 50 percent.
    • The above conditions are present for more than 2 seconds.

Conditions for Setting the DTC

The ECM detects that the actual MAF sensor voltage signal is not within a predetermined range of the calculated MAF value for more than 2 seconds.

Action Taken When the DTC Sets - California
    • 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.

Action Taken When the DTC Sets - Federal
    • The control module stores the DTC information into memory when the diagnostic runs and fails.
    • The malfunction indicator lamp (MIL) will not illuminate.
    • The control module records the operating conditions at the time the diagnostic fails. The control module stores this information in the Failure Records.
    • The driver information center, if equipped, may display a message.

Conditions for Clearing the MIL/DTC - California
    • 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.
    • Use a scan tool in order to clear the MIL and the DTC.

Conditions for Clearing the DTC - Federal
    • 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 non-emission related diagnostic.
    • Use a scan tool in order to clear the MIL and the DTC.

Diagnostic Aids

Inspect for the following conditions:

    • Any unmetered air--Any unmetered air that enters the engine downstream of the MAF sensor may cause this DTC to set.
    • A sluggish or unresponsive MAF sensor--A short between the signal circuit of the MAF sensor and the signal circuit of the intake air temperature (IAT) sensor. This will cause the MAF sensor to have a very limited output voltage range.
    • A malfunctioning MAF sensor can cause excessive engine emissions.
    • An open on the 5-volt reference circuit of the barometric pressure sensor (BARO) may cause this DTC to set.
    • A short to ground on the signal circuit of the BARO sensor may cause this DTC to set.
    • The signal circuit of the BARO sensor shorted to 5 volts may cause this DTC to set.
    • An open signal circuit of the BARO sensor may cause this DTC to set.
    • The MAF display should increase from 42-50 g/s at idle to 420 g/s or more at the 2-3 shift during a wide-open throttle (WOT) acceleration. If not, inspect for a restriction in the induction system or the exhaust system.
    • If the vehicle condition is intermittent, refer to Intermittent Conditions .

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. Start the engine
  2. 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 the Freeze Frame/Failure Records data for this DTC.
  2. Turn OFF the ignition for 30 seconds.
  3. Start the engine.
  4. Operate the vehicle within the Conditions for Running the DTC as specified in the supporting text or as close to the Freeze Frame/Failure Records data that you observed.

Does the DTC fail this ignition?

--

Go to Step 4

Go to Diagnostic Aids

4

Inspect the fuse in the ignition 1 voltage circuit of the MAF sensor.

Is the fuse open?

--

Go to Step  17

Go to Step 5

5
  1. Turn OFF the ignition.
  2. Inspect for air leaks in the following components:
    3. • A damaged MAF sensor housing
    • The air induction system and the turbocharger system
    • The charge air cooler with a J 46091 charge air cooler tester.
    • The MAF sensor O-ring seal
    • The boost pressure sensor seal
    • The EGR throttle valve solenoid , diaphragm, or vacuum hose
    • The EGR valve solenoid valve diaphragm, or vacuum hose
    • The EGR vent solenoid or vacuum hose
  3. Inspect for the following conditions:
    4. • Any kinks or restrictions in any of the EGR solenoid vacuum hoses
    • An obstructed intake air duct or a dirty air filter element
    • Any debris that is blocking the air sensing filaments of the MAF sensor
    • A MAF sensor that is installed backwards
    • A restricted exhaust system

Did you find and correct the condition?

--

Go to Step 26

Go to Step 6

6
  1. Turn ON the ignition, with the engine OFF.
  2. Observe both the BARO kPa and the boost pressure sensor kPa with a scan tool.

Does the scan tool indicate that the difference between the sensors is equal to or less than the specified value?

8 kPa

Go to Step 7

Go to DTC P0107 or DTC P0108

7
  1. Start the engine and allow the engine to idle.
  2. Observe the MAF sensor g/s with a scan tool.
  3. Move the harness and the connector of the MAF sensor.

Does the movement of the harness or the connector affect the MAF sensor g/s?

--

Go to Step 21

Go to Step 8

8

Observe the MAF sensor g/s with a scan tool.

Is the MAF sensor g/s less than the specified value?

16 g/s

Go to Step 11

Go to Step 9

9

Observe the MAF sensor g/s with a scan tool.

Is the MAF sensor g/s more than the specified value?

445 g/s

Go to Step 10

Go to Step 11

10

Disconnect the harness connector of the MAF sensor. Refer to Mass Airflow Sensor/Intake Air Temperature Sensor Replacement .

Is the MAF sensor g/s more than the specified value

445 g/s

Go to Step 15

Go to Step 11

11
  1. Turn OFF the engine.
  2. Turn ON the ignition, with the engine OFF.
  3. Disconnect the harness connector of the MAF sensor. Refer to Mass Airflow Sensor/Intake Air Temperature Sensor Replacement .
  4. 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 12

Go to Step 17

12

Important: All electrical components and accessories must be turned OFF.

  1. Turn OFF the ignition for 60 seconds to allow the control modules to power down.
  2. Measure the resistance from the ground circuit of the MAF sensor to a good ground with a DMM. Refer to Circuit Testing in Wiring Systems.

Is the resistance less than the specified value?

5ohms

Go to Step 13

Go to Step 18

13
  1. Turn ON the ignition, with the engine OFF.
  2. Connect a 3-amp fused jumper wire between the signal circuit of the IAT sensor and the signal circuit of the MAF sensor.
  3. Observe the MAF sensor value with a scan tool.

Did the MAF sensor value change to the specified value?

445 g/s

Go to Step 22

Go to Step 14

14
  1. Turn OFF the ignition.
  2. Disconnect the fused jumper wire.
  3. Disconnect the ECM. Refer to Engine Control Module Replacement .
  4. Test the signal circuit between the ECM and the MAF sensor for the following conditions:
    5. • A high resistance or an open
    • A short to ground
    • A short to the low reference circuit of the MAF sensor or IAT sensor--Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 26

Go to Step 16

15

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

  1. Turn OFF the ignition.
  2. Disconnect the ECM. Refer to Engine Control Module Replacement .
  3. Turn ON the ignition, with 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.

Does the voltage measure near the specified value?

0 V

Go to Step 16

Go to Step 19

16

Use a DMM in order to test for continuity at the harness connector of the ECM from the signal circuit of the MAF sensor to all other circuits at both ECM connectors. Refer to Circuit Testing in Wiring Systems.

Does the DMM indicate continuity between any other circuit?

--

Go to Step 20

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 26

Go to Step 24

18

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

Did you complete the repair?

--

Go to Step 26

Go to Step 23

19

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 26

--

20

Repair the circuits that are shorted together. Refer to Wiring Repairs in Wiring Systems.

Did you complete the repair?

--

Go to Step 26

--

21

Repair the harness or the connections as necessary. Refer to Wiring Repairs in Wiring Systems.

Did you complete the repair?

--

Go to Step 26

--

22

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

Did you find and correct the condition?

--

Go to Step 26

Go to Step 24

23

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

Did you find and correct the condition?

--

Go to Step 26

Go to Step 25

24

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

Did you complete the Replacement?

--

Go to Step 26

--

25

Replace the ECM. Refer to Engine Control Module Replacement .

Did you complete the Replacement?

--

Go to Step 26

--

26
  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 as specified in the supporting text.

Does the DTC run and pass?

--

Go to Step 27

Go to Step 2

27

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