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 DTC is designed to detect an unusually low MAF sensor signal frequency. If a MAF sensor frequency is detected by the VCM below the possible range of a normally operating MAF sensor, this DTC will be set.
Conditions for Running the DTC
| • | The engine run time is greater than 0.4 seconds. |
| • | The engine speed is greater than 300 RPM. |
| • | The system voltage is greater than 8 volts. |
Conditions for Setting the DTC
The MAF frequency is 10 Hz or less for more than 1 second.
Action Taken When the DTC Sets
| • | The VCM illuminates the Malfunction Indicator Lamp (MIL) the first time the fault is detected. |
| • | The VCM calculates an airflow value based on the Idle Air Control (IAC) valve position, throttle position, engine speed and barometric pressure. |
| • | The VCM stores the conditions which were present when the DTC set as Freeze Frame and the Fail Records data. |
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 poor connection at the VCM. Inspect harness connectors for the following conditions: |
| - | Backed out terminals |
| - | Improper mating |
| - | Broken locks |
| - | Improperly formed or damaged terminals |
| - | Poor terminal to wire connection |
| • | 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 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 greater at the time of the 1-2 shift. If not, check for a restriction. |
Test Description
The numbers below refer to step numbers on the diagnostic table.
-
This step verifies that the problem is present at idle.
-
A voltage reading of less than 4 or over 6 volts at the MAF sensor signal circuit indicates a fault in the wiring or a poor connection
-
This step verifies that the ignition feed 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. Refer to Fuse Block Details in Electrical Diagnosis.
Step | Action | Value(s) | Yes | No | ||||||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
1 |
Important: Before clearing the DTCs, use the scan tool in order to record the Freeze Frame and the Failure Records for reference. This data will be lost when the Clear DTC Information function is used. Was the Powertrain On-Board Diagnostic (OBD) System Check performed? | -- | ||||||||||||||||||
Is the MAF reading below the specified value? | 2 g/s | |||||||||||||||||||
3 |
Does the scan tool indicate DTC P0102 failed this ignition? | -- | Go to Diagnostic Aids | |||||||||||||||||
4 | Inspect the MAF Ignition Positive Voltage Fuse. Is the fuse open? | -- | ||||||||||||||||||
5 |
Was a problem found? | -- | ||||||||||||||||||
Is the voltage near the specified value? | 5.0 V | |||||||||||||||||||
Connect a test lamp between the MAF sensor ignition feed and ground circuits at the MAF sensor harness connector. Is the test lamp ON? | -- | |||||||||||||||||||
8 | Connect a test lamp between the MAF sensor ignition feed circuit and the battery ground. Is the test lamp ON? | -- | ||||||||||||||||||
9 | Check for a poor connection at the MAF sensor. If a poor connection is found, replace faulty terminals. Refer to Wiring Repairs in Repair Instructions. Was a poor connection found? | -- | ||||||||||||||||||
10 |
Was the MAF signal circuit open or shorted? | -- | ||||||||||||||||||
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 |
Is the action complete? | -- | -- | |||||||||||||||||
16 |
Does the scan tool indicate that this diagnostic ran and passed? | -- | ||||||||||||||||||
17 | Use the scan tool in order to display the Capture Info and the Review Capture Info functions. Are any DTCs displayed that have not been diagnosed? | -- | Go to Applicable DTC Tables | System OK |
