GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 GMC_Truck 🢒 2002 🢒 GMC C Sierra - 2WD 🢒 Engine 🢒 Engine Controls - 8.1L 🢒 DTC P0102

Circuit Description

The mass air flow (MAF) sensor is an airflow meter that measures the amount of air entering the engine. The powertrain control module (PCM) uses the MAF sensor 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 high load condition. The MAF sensor has the following circuits:

    • An ignition 1 voltage circuit
    • A ground circuit
    • 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 inlet air flow through the sensor bore. The frequency varies within a range of around 2,000 Hertz at idle to about 10,000 Hertz at maximum engine load. If the PCM detects a frequency signal lower than the possible range of a properly operating MAF sensor, DTC P0102 sets.

Conditions for Running the DTC
    • The engine is running for more than 2 seconds.
    • The engine speed is more than 400 RPM.
    • The ignition 1 signal is more than 8 volts.
    • The MAF sensor frequency is stable for more than 1 second.

Conditions for Setting the DTC

The PCM detects that the MAF sensor frequency signal is less than 1,300 Hertz.

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:

    • An incorrectly routed harness--Inspect the harness of the MAF sensor in order to verify that it is not routed too close to the following components:
       - The secondary ignition wires or coils
       - Any solenoids
       - Any relays
       - Any motors
       - Any aftermarket accessories--Refer to Checking Aftermarket Accessories in Wiring Systems.
    • A low minimum air rate through the sensor bore may cause this DTC to set at idle or during deceleration. Inspect for any vacuum leaks downstream of the MAF sensor.
    • A wide open throttle (WOT) acceleration from a stop should cause the MAF sensor g/s display on the scan tool to increase rapidly. This increase should be from 6-12 g/s at idle to 230 g/s or more at the time of the 1-2 shift. If the increase is not observed, inspect for a restriction in the induction system or the exhaust system.
    • A resistance of 15 ohms or more on the ground circuit or the ignition 1 circuit of the MAF sensor can cause this DTC to set.

If you suspect the condition may be related to aftermarket accessories, refer to Checking Aftermarket Accessories in Wiring Systems.

If the condition is intermittent, refer to Intermittent Conditions .

Test Description

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

  1. This step will determine if any mechanical faults have caused this DTC to set.

    2.

  2. This voltage drop test will determine if high resistance has caused this DTC to set.

    3.

  3. This step verifies the voltage signal from the PCM to the MAF sensor connector.

    4.

  4. This step tests the signal circuit of the MAF sensor for a short to another 5-volt reference circuit.

    5.

  5. This step will determine which portion of the circuit or which component is shorted to ground.

    6.

  6. This step verifies that the signal circuit is not shorted to any other PCM circuit.

Step

Action

Values

Yes

No

Schematic Reference: Engine Controls Schematics

Connector End View Reference: Engine Controls Connector End Views or Powertrain Control Module Connector End Views

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. Observe the mass air flow (MAF) sensor parameter with a scan tool.

Is the MAF sensor parameter less than the specified value?

1,300 Hz

Go to Step 4

Go to Step 3

3
  1. Observe the Freeze Frame/Failure Records 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. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records.

Did the DTC fail this ignition?

--

Go to Step 4

Go to Diagnostic Aids

4
  1. Observe the MAF sensor parameter with a scan tool.
  2. Move the harness and the connector of the MAF/intake air temperature (IAT) sensor.

Does the movement of the harness or the connector affect the MAF sensor parameter?

--

Go to Step 19

Go to Step 5

5

  1. Turn OFF the ignition.
  2. Inspect for the following conditions:
    3. • A restricted or collapsed air intake duct
    • A misaligned air intake duct
    • A dirty or deteriorating air filter element
    • Any objects blocking the air inlet screen of the MAF sensor
    • A restricted exhaust system
    • Any contamination or debris on the sensing elements of the MAF sensor

Did you find and correct the condition?

--

Go to Step 27

Go to Step 6

6

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

Is the fuse open?

--

Go to Step 13

Go to Step 7

7

  1. Turn ON the ignition, with the engine OFF.
  2. Measure the battery voltage with a DMM.
  3. Disconnect the MAF/IAT sensor.
  4. Connect a test lamp between the ignition 1 voltage circuit of the MAF sensor and a good ground. Refer to Probing Electrical Connectors in Wiring Systems.
  5. Connect the DMM to the probe of the test lamp and a good ground. Refer to Circuit Testing in Wiring Systems.

Is the voltage less than the specified value?

B+

Go to Step 20

Go to Step 8

8

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?

5 ohms

Go to Step 9

Go to Step 21

9

  1. Turn ON the ignition, with the engine OFF.
  2. Measure the voltage from the signal circuit of the MAF sensor to a good ground with a DMM. Refer to Circuit Testing in Wiring Systems.

Is the voltage within the specified range?

4.8-5.2 V

Go to Step 10

Go to Step 12

10

  1. Connect a 3-amp fused jumper wire between the signal circuit of the MAF sensor and a good ground. Refer to Circuit Testing in Wiring Systems.
  2. Start the engine.
  3. Observe the DTC Information with a scan tool.

Do any additional DTCs set?

--

Go to Step 23

Go to Step 11

11

Important: An abnormal resistance on the signal circuit will disable the MAF sensor frequency before the voltage starts to drop out of the correct parameter of: 4.8 to 5.2 V.

Test the MAF sensor signal circuit for a high resistance.

Did you find and correct the condition?

--

Go to Step 27

Go to Step 17

12

Is the voltage less than the specified value?

4.8 V

Go to Step 14

Go to Step 15

13

Important:: The ignition 1 voltage circuit of the MAF sensor is spliced to other components of the vehicle.

Test the ignition 1 voltage circuit for a short to ground. Refer to Testing for Short to Ground and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 27

--

14
  1. Turn OFF the ignition.
  2. Disconnect the powertrain control module (PCM).
  3. Test the signal circuit between the PCM and the MAF sensor for the following conditions:
    4. • A high resistance
    • An open circuit
    • A short to ground

Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 27

Go to Step 16

15

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.
  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 with a DMM. Refer to Circuit Testing in Wiring Systems.

Is the voltage more than the specified value?

0 V

Go to Step 22

Go to Step 16

16

Measure the resistance from the signal circuit of the MAF sensor to all other circuits at both PCM connectors with a DMM. Refer to Circuit Testing in Wiring Systems.

Is the resistance less than the specified value?

∞

Go to Step 24

Go to Step 18

17

Test for an intermittent and for a poor connection at 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 27

Go to Step 25

18

Test for an intermittent and for a poor connection at the PCM. 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 27

Go to Step 26

19

Repair the wiring or the connector as needed. Refer to Wiring Repairs and Connector Repairs in Wiring Systems.

Did you complete the repair?

--

Go to Step 27

--

20

Repair the high resistance or the open in the MAF sensor ignition 1 voltage circuit. Refer to Wiring Repairs in Wiring Systems.

Did you complete the repair?

--

Go to Step 27

--

21

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

Did you complete the repair?

--

Go to Step 27

--

22

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

Did you complete the repair?

--

Go to Step 27

--

23

Repair the short between the MAF sensor signal circuit and the 5 V reference circuit for which the DTC set. Refer to Wiring Repairs in Wiring Systems.

Did you complete the repair?

--

Go to Step 27

--

24

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

Did you complete the repair?

--

Go to Step 27

--

25

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

Did you complete the replacement?

--

Go to Step 27

--

26

Replace the PCM. Refer to Powertrain Control Module Replacement .

Did you complete the replacement?

--

Go to Step 27

--

27
  1. Clear the DTCs with a scan tool.
  2. Turn OFF the ignition for 30 seconds.
  3. Start the engine.
  4. 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.

Did the DTC fail this ignition?

--

Go to Step 2

Go to Step 28

28

Observe the Capture Info with a scan tool.

Are there any DTCs that have not been diagnosed?

--

Go to Diagnostic Trouble Code (DTC) List

System OK