P0102

DTC P0102

CIRCUIT DESCRIPTION
The mass air flow (MAF) sensor is an air flow meter that measures the amount of air entering the engine. The MAF sensor used on this engine is a hot film meter (HFM) type. The engine control module (ECM) applies a voltage to the sensor on the signal circuit. The sensor uses the voltage to produce a frequency based on the inlet air flow through the sensor bore. The frequency varies within a range of near 2,500 Hertz at idle to near 2,000 10,000 Hertz at maximum engine load. The MAF sensor frequency signal is a function of the current required to keep the air flow sensing element at a fixed temperature above ambient. The air flowing through the sensor cools the sensing element. The amount of cooling is proportional to the amount of the air flow. As the air flow increases, more current is required to maintain the hot film at a constant temperature. The ECM uses the MAF sensor signal to provide the correct fuel delivery for a wide range of engine speeds and loads. The MAF sensor uses the following circuits to operate:
- A 12-volt reference circuit
- A low reference circuit that is shared with the intake air temperature (IAT) sensor
- A signal circuit

The 12-volt reference circuit of the MAF sensor is also supplied to additional sensors and they are connected within the ECM. The 12-volt reference is shared by the following sensors:
- The MAF sensor
- The crankshaft position (CKP) sensor
- The camshaft position (CMP) sensor bank 1 intake
- The CMP sensor bank 1 exhaust
- The CMP sensor bank 2 intake
- The CMP sensor bank 2 exhaust

If the ECM detects the frequency signal is less than the possible range of a correctly operating MAF sensor DTC P0102 sets.

DTC DESCRIPTOR
This diagnostic procedure supports the following DTC:
DTC P0102 Mass Air Flow (MAF) Sensor Circuit Low Frequency

CONDITIONS FOR RUNNING THE DTC
- The engine is running.
- The Engine Speed parameter is more than 544 RPM.
- This DTC runs continuously in a 12.5-millisecond loop.

CONDITIONS FOR SETTING THE DTC
The ECM detects that the MAF sensor frequency signal is less than 200 Hertz for more than 200 milliseconds.

ACTION TAKEN WHEN THE DTC SETS
- The control module illuminates the malfunction indicator lamp (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails.
- The control module records the operating conditions at the time the diagnostic fails. The first time the diagnostic fails, the control module stores this information in the Failure Records. If the diagnostic reports a failure on the second consecutive ignition cycle, the control module records the operating conditions at the time of the failure. The control module writes the operating conditions to the Freeze Frame and updates the Failure Records.

CONDITIONS FOR CLEARING THE MIL/DTC
- The control module turns OFF the malfunction indicator lamp (MIL) after 3 consecutive ignition cycles that the diagnostic runs and does not fail.
- A current DTC, Last Test Failed, clears when the diagnostic runs and passes.
- A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic.
- Clear the MIL and the DTC with a scan tool.

DIAGNOSTIC AIDS
- A wide open throttle acceleration from a stop should cause the MAF sensor parameter on the scan tool to increase rapidly. This increase should be from 4-10 g/s at idle to 210 g/s or more at the time of the 1-2 shift.
- A high resistance of 15 ohms or more on the 12-volt reference circuit may cause this DTC to set. A high resistance will cause a driveability concern before this DTC sets.
- A high resistance of 10 ohms or more on the ground circuit may cause this DTC to set. A high resistance will cause a driveability concern before this DTC sets.
- A short between the MAF sensor 12-volt reference circuit and the IAT signal circuit will produce a stalling condition that becomes a Crank/No Start condition.
- If the condition is intermittent, refer to Inducing Intermittent Fault Conditions in Diagnostic Aids and Intermittent Conditions. Component Tests and General Diagnostics

TEST DESCRIPTION

Step 1 - Step 6:

Step 7 - Step 13:

Step 14 - Step 20:

Step 21 - Step 28:

The numbers below refer to the step numbers on the diagnostic table.
4. This step will determine if a shorted component has caused this DTC to set.
5. This step will determine if a shorted component has caused this DTC to set.
6. This step will determine if any mechanical faults have caused this DTC to set.
7. This voltage drop test will determine if high resistance has caused this DTC to set.
9. This step verifies the voltage signal from the ECM to the MAF sensor connector.
11. This step will determine if the ECM can accurately process the frequency signal that it receives from the MAF sensor.
12. This step will determine if an abnormal resistance of less than 1,150 ohms has skewed the MAF sensor frequency signal.