P0102

Circuit Description
The Mass Air Flow (MAF) sensor measures the amount of air that is ingested by the engine. Direct measurement of air entering the engine is more accurate than calculating airflow from Other sensor inputs. The MAF sensor has a ignition feed, a ground, and a signal circuit.

The MAF sensor used on this vehicle is a hot wire type and is used to measure air flow rate. The frequency of the MAF sensor signal is a function of the power required to keep the air flow sensing elements at a fixed temperature above ambient temperature. Air flowing through the sensor cools the sensing elements. The amount of cooling is proportional to the amount of air flow. As air flow increases, a greater amount of current is required to maintain the hot wire at a constant temperature. The MAF sensor converts the changes in current draw to a frequency signal read by the PCM. The frequency typically varies from about 2 kHz at idle to about 10 kHz at maximum engine load. The PCM calculates air flow based on this signal.

The PCM monitors the MAF sensor signal frequency and can determine if the sensor signal voltage is too low, too high, or not indicating the expected airflow for a given operating condition.

Conditions for Running the DTC
^ The engine is running.
^ TP angle is less than 50%.
^ System voltage is greater than 8 volts.
^ IAC above 2 counts

Conditions for Setting the DTC
^ MAF signal frequency is less than 1200 Hertz.
^ The above conditions are present for approximately 2 seconds

Action Taken When the DTC Sets
^ The PCM illuminates the Malfunction Indicator Lamp on the second consecutive ignition cycle that the diagnostic runs and fails.
^ The PCM records the operating conditions at the time the diagnostic fails. The first time the diagnostic fails, the PCM stores this information in the Failure Records. If the diagnostic reports a failure on the second consecutive ignition cycle, the PCM records the operating conditions at the time of the failure. The PCM writes the conditions to the Freeze Frame and updates the Failure records.

The PCM calculates an airflow value based on idle air control valve position, Throttle position, RPM and barometric pressure.

Conditions for Clearing the MIL/DTC
^ The PCM turns the MIL Oft after three consecutive drive trips that the diagnostic runs and does not fail.
^ A last test failed (current DTC) clears when the diagnostic runs and does not fail.
^ A History DTC clears after forty consecutive warm-up cycles, if this or any Other emission related diagnostic does not report any failures.
^ Use a scan tool in order to clear the MIL/DTC.
^ Interrupting the PCM battery voltage may or may not clear DTCs. This practice is not recommended.

Diagnostic Aids

Notice: Use the Connector Test Adapter Kit J 35616-A for any test that requires probing the following items:
^ The PCM harness connectors
^ The electrical center fuse/relay cavities
^ The component terminals
^ The component harness connector

Using this kit will prevent damage caused by the improper probing of connector terminals.

A low minimum air rate can cause DTC P0102 to be set during deceleration. Check the minimum air rate as follows:
1. Run the engine until fully warm (above 85°C/185°F).
2. Disconnect the IAC.
3. Install a J 37027-A IAC System Monitor.
4. With the engine idling, command the IAC valve to the fully extended position (0 counts).
5. With the IAC fully extended, observe the Mass Air Flow reading on the scan tool.
6. Check for conditions that can cause a low minimum air rate, including Throttle bore and Throttle plate coking if the Mass Air Flow reading is less than 2.27 g/sec.
7. If the minimum air rate is less than specifications, clean or replace the Throttle body as necessary..
8. Check for 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 gm/s at idle to 100 gm/s or greater at the time of the 1-2 shift. If not, check for a restriction.

If DTC P0102 cannot be duplicated, the information included in the Fail Records data can be useful in determining vehicle mileage since the DTC was last set. This may assist in diagnosing the condition.

Test Description
Number(s) below refer to the step number(s) on the Diagnostic Table:
2. This step verifies that the problem is present at idle.
5. 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.
6. Verifies that ignition feed voltage and a good ground are available at the MAF sensor.
13. This vehicle is equipped with a PCM which utilizes an Electrically Erasable Programmable Read Only Memory (EEPROM). When the PCM is being replaced, the new PCM must be programmed.