Circuit Description
The mass air flow (MAF) sensor is an air flow meter. The control module supplies the MAF sensor a signal circuit. An ignition positive voltage circuit and a ground circuit are supplied to the MAF sensor by independent circuits. The MAF sensor heats a wire element, or grid, within the MAF sensor in order to maintain a calculated temperature. As inlet air flows across and cools the grid, the MAF sensor increases current flow to the grid in order to maintain the constant grid temperature. The MAF sensor converts the grid current flow into a frequency signal. The control module converts the MAF signal frequency into a grams per second value. During low air flow rates, such as at engine idle, the MAF sensor produces a low frequency signal. During high air flow rates, such as at wide open throttle-road load, the MAF sensor increases the frequency signal. The control module monitors the MAF sensor signal frequency in order to calculate the flow and mass of the air entering the engine.
This diagnostic trouble code (DTC) is designed in order to detect an unusually low MAF sensor signal frequency. If a MAF sensor frequency is detected by the vehicle control module (VCM) below the possible range of a normally operating MAF sensor, this DTC will be set.
Conditions for Running the DTC
Power Up Test
| • | The engine is OFF. |
| • | The ignition is ON for 2 seconds. |
Low Frequency Test
| • | The engine speed is more than 300 RPM. |
| • | The engine run time is more than 2 seconds. |
| • | The system voltage is more than 10 volts. |
| • | The throttle position is less than 50 percent. |
| • | The above conditions are present for more than 2 seconds. |
Conditions for Setting the DTC
Power Up Test
The MAF frequency is less than 60 Hz for more than 250 ms.
Low Frequency Test
The MAF frequency is less than 300 Hz for more than 250 ms.
Action Taken When the DTC Sets
| • | The control module illuminates the malfunction indicator lamp (MIL) if a failure is detected during 2 consecutive key cycles. |
| • | The control module sets the DTC and records the operating conditions at the time the diagnostic failed. The failure information is stored in the scan tool Freeze Frame/Failure Records. |
Conditions for Clearing the MIL or DTC
| • | The control module turns OFF the MIL after 3 consecutive drive trips when the test has run and passed. |
| • | A history DTC will clear if no fault conditions have been detected for 40 warm-up cycles. A warm-up cycle occurs when the coolant temperature has risen 22°C (40°F) from the startup coolant temperature and the engine coolant reaches a temperature that is more than 70°C (158°F) during the same ignition cycle. |
| • | Use a scan tool in order to clear the DTCs. |
Diagnostic Aids
Check for the following conditions:
| • | A misrouted harness -- Inspect the MAF sensor harness in order to ensure that it is not routed too close to high voltage wires such as spark plug leads. |
| • | A damaged harness -- Inspect the wiring harness for damage. If the harness appears to be OK, observe the scan tool while moving the connectors and the wiring harnesses related to the MAF sensor. A change in the display indicates the location of the fault. |
| • | A plugged intake air duct or filter element -- A wide open throttle (WOT) acceleration from a stop should cause the Mass Air Flow displayed on a scan tool to increase from about 4-7 g/s at idle to 100 g/s or more at the time of the 1-2 shift. If not, check for a restriction. |
An intermittent may be caused by any of the following conditions:
| • | A poor connection |
| • | Rubbed through wire insulation |
| • | A broken wire inside the insulation |
Thoroughly inspect any circuitry that is suspected of causing the intermittent complaint. Refer to Testing for Intermittent Conditions and Poor Connections in Wiring Systems.
If a repair is necessary, refer to Wiring Repairs or Connector Repairs in Wiring Systems.
Test Description
The numbers below refer to the step numbers on the diagnostic table.
-
This step verifies that the problem is present at idle.
-
A voltage reading of less than 4 or more than 6 volts at the MAF sensor signal circuit indicates a malfunction in the wiring or a poor connection.
-
This step verifies that the ignition positive voltage and a good ground are available at the MAF sensor.
-
This step determines if the fuse is open. If the fuse is open, locate and repair the short to ground in the ignition positive voltage circuit.
Step | Action | Value(s) | Yes | No | ||||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
1 | Did you perform the Powertrain On-Board Diagnostic (OBD) System Check? | -- | ||||||||||||||||
Is the MAF reading below the specified value? | 2 g/s | |||||||||||||||||
3 |
Does the scan tool indicate that DTC P0102 Failed This Ignition? | -- | Go to Diagnostic Aids | |||||||||||||||
4 | Inspect the MAF ignition positive voltage fuse. Is the fuse open? | -- | ||||||||||||||||
5 |
Did you find a problem? | -- | ||||||||||||||||
Is the voltage near the specified value? | 5.0 V | |||||||||||||||||
Connect a test lamp between the MAF sensor ignition positive voltage and ground circuits at the MAF sensor harness connector. Is the test lamp ON? | -- | |||||||||||||||||
8 | Connect a test lamp between the MAF sensor ignition positive voltage circuit and the battery ground. Is the test lamp ON? | -- | ||||||||||||||||
9 |
Did you find a problem? | -- | ||||||||||||||||
10 |
Did you find a problem? | -- | ||||||||||||||||
Is the action complete? | -- | -- | ||||||||||||||||
12 |
Is the action complete? | -- | -- | |||||||||||||||
13 |
Is the action complete? | -- | -- | |||||||||||||||
14 | Replace the MAF sensor. Refer to Mass Airflow Sensor Replacement . Is the action complete? | -- | -- | |||||||||||||||
15 |
Did you find a problem? | -- | ||||||||||||||||
16 |
Important: The replacement VCM must by programmed. Replace the VCM. Refer to VCM Replacement/Programming . Is the action complete? | -- | -- | |||||||||||||||
17 |
Does the scan tool indicate that the diagnostic Passed? | -- | ||||||||||||||||
18 | Does the scan tool display any additional undiagnosed DTCs? | -- | Go to the applicable DTC table | System OK |
