P0102
DTC P0102 MAF Sensor Circuit Low Frequency
Circuit Description
The Mass Air Flow (MAF) sensor is a hot wire type air flow meter. The MAF sensor uses ignition voltage, a ground and a signal circuit. The signal circuit is the input to the VCM. The MAF heats a wire element in the air flow stream to a predetermined temperature. As inlet air flows across and cools the wire element, the MAF sensor increases current flow to the wire element in order to maintain a constant element temperature. The MAF sensor converts this current flow into a frequency signal. The VCM monitors the MAF signal frequency and determines the flow and mass of the air entering the engine.
The VCM converts the MAF signal frequency into a grams per second value. During low air flow rates (such as at engine idle) the MAF sensor will produce a low frequency signal (approximately 2000 Hz or 6 grams/second). During high air flow rates such as wide open throttle at road load, the MAF sensor will produce a high frequency signal (approximately 9000 HZ or 125 grams/second).
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 is running
- The engine run time is more 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 MIL (Malfunction Indicator Lamp) if a failure is detected during 2 consecutive key cycles.
- The VCM will set the DTC and records the operating conditions at the time the diagnostic fails. The VCM stores the failure information in the scan tools Freeze Frame and/or the Failure Records.
Conditions for Clearing the MIL/DTC
- The VCM 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 (coolant temperature has risen 22 °C (40 °F) from the startup coolant temperature and the engine coolant temperature is more than 70 °C (158 °F) during the same ignition cycle).
- Use the scan tool Clear Information function.
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 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.
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 check any circuitry that is suspected of causing the intermittent complaint. Refer to Intermittents and Poor Connections Diagnosis.
If a repair is necessary, then refer to Wiring Repairs or Connector Repairs.
Steps 1 - 4:
Steps 5 - 9:
Steps 10 - 15:
Steps 16 - 18:
Step 18:
Test Description
The numbers below refer to step numbers on the diagnostic table.
2. This step verifies that the problem is present at idle.
6. A voltage reading of less than 4 or over 6 volts at the MAF sensor signal circuit indicates a malfunction in the wiring or a poor connection.
7. This step verifies that the ignition feed voltage and a good ground are available at the MAF sensor.
11. 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 Electrical Center Identification.