GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 GMC_Truck 🢒 2004 🢒 TopKick C-Series (Conventional) C4/C5 🢒 DTC 🢒 DTC P0102

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 to provide the correct fuel delivery for a reduction in emissions. The ECM uses the MAF sensor signal 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 the inlet air flow through the air induction system. This output voltage will display on the scan tool as a voltage parameter and as a grams per second (g/s) parameter. If the ECM detects that the actual MAF sensor voltage signal is less than the possible range of a normally operating sensor DTC P0102 sets.

DTC Descriptor

This diagnostic procedure supports the following DTC:

DTC P0102 Mass Air Flow (MAF) Sensor Circuit Low Voltage.

Conditions for Running the DTC
    • The engine is running for more than 2 seconds.
    • The engine speed is more than 500 RPM.
    • The ignition 1 signal is more than 9 volts.
    • The above conditions are present for more than 3 seconds.
    • DTC P0102 runs continuously within the enabling conditions.

Conditions for Setting the DTC

The ECM detects that the MAF sensor voltage signal is less than 0.42 volt for more than 6 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
    • The MAF Sensor parameter should increase from 24-50 g/s at idle to 320 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 condition is intermittent, refer to Intermittent Conditions and Inducing Intermittent Fault Conditions in Wiring Systems.

Step

Action

Values

Yes

No

Schematic Reference: Engine Controls Schematics

Connector End View Reference: Engine Controls Connector End Views or Engine 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

Start the engine.

Does the engine have fuel knock/combustion noise?

--

Go to Step 5

Go to Step 3

3
  1. Allow the engine to idle.
  2. Observe the MAF Sensor parameter with a scan tool.

Is the MAF Sensor parameter less than the specified value?

0.42 V

Go to Step 6

Go to Step 4

4
  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 6

Go to Diagnostic Aids

5

With the engine running , disconnect the mass air flow (MAF)/intake air temperature (IAT) sensor.

Does the engine have fuel knock/combustion noise?

--

Go to Step 12

Go to Step 15

6
  1. Observe the MAF Sensor parameter with a scan tool.
  2. Move the harness and the connector of the MAF/IAT sensor.

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

--

Go to Step 19

Go to Step 7

7
  1. Turn OFF the ignition.
  2. Inspect for air leaks in the following components:
    3. • The air induction system and the turbocharger system
    • The MAF sensor O-ring seal
    • The boost pressure sensor seal
  3. Inspect for the following conditions:
    4. • An obstructed intake air duct or a dirty air filter element
    • Any debris that is blocking the air sensing filaments of the MAF sensor
    • Contamination on the air sensing filaments of the MAF sensor
    • Water intrusion in the air induction system
    • A MAF sensor that is installed backwards
    • A restricted exhaust system--Refer to Restricted Exhaust in Engine Exhaust

Did you find and correct the condition?

--

Go to Step  22

Go to Step 8

8

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

Is the fuse open?

--

Go to Step 11

Go to Step 9

9
  1. Turn ON the ignition, with the engine OFF.
  2. Measure the battery voltage with a DMM.
  3. Disconnect the harness connector of 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 and Circuit Testing in Wiring Systems.
  5. Connect the DMM to the probe of the test lamp and a good ground. Refer to Measuring Voltage Drop and Circuit Testing in Wiring Systems.

Is the voltage within 1.5 volts of the specified value?

B+

Go to Step 10

Go to Step 17

10
  1. Connect a 3-amp fused jumper wire between the ignition 1 voltage circuit of the MAF sensor and the signal circuit of the MAF sensor. Refer to Circuit Testing in Wiring Systems.
  2. Observe the MAF Sensor parameter with a scan tool.

Is the MAF Sensor parameter more than the specified value?

445 g/s

Go to Step 15

Go to Step 13

11

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

Test the MAF sensor ignition 1 voltage circuit for the following conditions:

    • A short to ground
    • Any shorted component on the spliced circuit
         Refer to Testing for Short to Ground and Circuit Testing and Wiring Repairs in Wiring Systems.

Did you complete the action?

--

Go to Step 22

--

12
  1. Turn OFF the ignition.
  2. Disconnect the engine control module (ECM).
  3. Test the MAF sensor ignition 1 voltage circuit for the following conditions:
    4. • A short to the MAF sensor low reference circuit
    • A short to the IAT sensor low reference circuit-- Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 22

Go to Step 16

13
  1. Turn OFF the ignition.
  2. Disconnect the fused jumper wire.
  3. Disconnect the ECM.
  4. Test the MAF sensor signal circuit for the following conditions:
    5. • A high resistance or an open
    • A short to ground
    • A short to the IAT sensor low reference circuit
    • A short to the MAF sensor low reference circuit
    •  Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 22

Go to Step 14

14

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

Is the resistance less than the specified value?

∞ ohms

Go to Step 18

Go to Step 16

15

Test for shorted terminals and for an intermittent and for a poor connection at the MAF/IAT sensor. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs and Repairing Connector Terminals in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 22

Go to Step 20

16

Test for shorted terminals and for an intermittent and for a poor connection at the ECM. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs and Repairing Connector Terminals in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 22

Go to Step 21

17

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 22

--

18

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

Did you complete the repair?

--

Go to Step 22

--

19

Repair the harness or the connections as necessary. Refer to Connector Repairs and Repairing Connector Terminals and Wiring Repairs in Wiring Systems.

Did you complete the repair?

--

Go to Step 22

--

20

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

Did you complete the replacement?

--

Go to Step 22

--

21

Replace the ECM. Refer to Engine Control Module Replacement .

Did you complete the replacement?

--

Go to Step 22

--

22
  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 23

23

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