P0102

CIRCUIT DESCRIPTION
The Mass Air Flow (MAF) sensor measures the amount of air entering the engine during a given time. The VCM uses the Mass Air Flow information for fuel delivery calculations. A large quantity of air entering the engine indicates an acceleration or high load situation, while a small quantity of air indicates deceleration or idle.

The MAF sensor produces a frequency signal which can be monitored using a scan tool. The frequency varies within a range of around 5 to 7 g/s at idle to near 125 g/s at maximum engine load. This DTC sets if the signal from the MAF senor measures below the possible range of a normally operating MAF sensor. This DTC is a type A DTC.

CONDITIONS FOR SETTING THE DTC

Power Up Test
^ The engine is off.
^ The ignition is ON for 2 seconds.
^ The MAF sensor is no more than 2 g/s or greater than 300 g/s.

Low Frequency Test
^ The engine is running.
^ Engine run time is greater than 2 seconds.
^ System voltage is at least 10.0 volts.
^ Throttle Position is less than 89.8%.
^ MAF signal frequency is no more than 2 g/s.
^ Above conditions present for over 2 seconds.

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 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/DTC
^ The VCM turns the MIL off on the third consecutive trip cycle during which the diagnostic has been run and the fault condition is no longer present.
^ A history DTC clears after 40 consecutive warm-up cycles have occurred without a fault.
^ Using the scan tool Clear Info function or disconnecting the VCM battery feed clears the DTC.

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 gm/s at idle to 100 gm/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.

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 fault in the wiring or a poor connection.
6. This step verifies that the ignition feed voltage and a good ground are available at the MAF sensor.

13. This vehicle is equipped with a VCM. The VCM utilizes an Electricity Erasable Programmable Read Only Memory (EEPROM). When the VCM is being replaced, reprogram the VCM. Refer to VCM Replacement/Programming.