Circuit Description
The DTC P0102 Mass Air Flow (MAF) Sensor Circuit Low Voltage diagnostic detects an out of range sensor signal. The MAF sensor measures the changes in the intake air volume that result from the changes in throttle opening and air density. Air flow measurements are used by the powertrain control module (PCM) in order to determine engine fueling requirements.
The MAF sensor is a hot wire design. A platinum hot wire and a thermistor are located in the intake air bypass passage of the MAF sensor housing. The temperature of the platinum hot wire is affected by exposure to air flow and by exposure to air temperature. The platinum hot wire is maintained at a set temperature by controlling the current flow through the wire. The MAF sensor converts the changes in current flow to a voltage signal. The voltage signal from the MAF sensor enables the PCM to detect changes in air density and changes in air volume.
Conditions for Running the DTC
| • | The ignition is ON or the engine is running. |
| • | DTC P0102 runs continuously once the above condition has been met. |
Conditions for Setting the DTC
| • | The MAF sensor signal is less than 0.2 volts. |
| • | The condition is present for at least 3 seconds. |
Action Taken When the DTC Sets
| • | The PCM illuminates the malfunction indicator lamp (MIL). |
| • | The PCM records the operating conditions at the time the diagnostic fails. This information will be stored in the Freeze Frame buffer. |
| • | The PCM enters the Fail-Safe Function and operates with the ignition timing fixed at 5 degrees before top dead center (BTDC). |
Conditions for Clearing the MIL/DTC
| • | The MIL turns OFF after 3 consecutively passing cycles without a fault present. |
| • | A History DTC will clear after 40 consecutive warm-up cycles without a fault. |
| • | Perform the scan tool clear DTC Information Function in order to clear the DTC. |
Test Description
The numbers below refer to the step numbers on the diagnostic table.
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The Diagnostic System Check - Engine Controls prompts the technician to complete some basic checks and store the Freeze Frame data on the scan tool if applicable. This creates an electronic copy of the data taken when the fault occurred. The information is then stored in the scan tool for later reference.
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This step checks for a low input signal from the MAF sensor.
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This step is looking for MAF sensor output on the MAF signal high circuit. Air movement around the sensor's hot wire element can cause some fluctuation in the voltage being measured.
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This step tests for a short to ground in the MAF signal high circuit. If the test lamp illuminates, there is a short to ground in the circuit or PCM. If the test lamp does not illuminate, the circuit may be OK or may have an open.
Step | Action | Values | Yes | No |
|---|---|---|---|---|
Schematic Reference: Engine Controls Schematics Connector End View Reference: Powertrain Control Module Connector End Views or Engine Controls Connector End Views | ||||
Did you perform the Diagnostic System Check - Engine Controls? | -- | Go to Step 2 | ||
Select the MAF sensor parameter on the scan tool. Is the MAF sensor less than or equal to the specified value? | 0.45 g/s | Go to Step 4 | Go to Step 3 | |
3 |
Does a DTC P0102 set? | -- | Go to Step 4 | Go to Intermittent Conditions |
4 |
Is the test lamp illuminated? | -- | Go to Step 5 | Go to Step 6 |
Is the MAF signal high voltage within the specified range? | 0.5-3.0 V | Go to Step 7 | Go to Step 8 | |
6 | Repair the open in the MAF sensor ignition positive voltage circuit. Refer to Wiring Repairs in Wiring Systems. Did you complete the repair? | -- | Go to Step 15 | -- |
7 |
Did the signal high circuit voltage increase when blowing air into the sensor orifice? | -- | Go to Step 11 | Go to Step 12 |
Is the test lamp illuminated? | -- | Go to Step 10 | Go to Step 9 | |
9 |
Did you find and correct a condition? | -- | Go to Step 15 | Go to Step 12 |
10 |
Did you find and correct a condition? | -- | Go to Step 15 | Go to Step 14 |
11 |
Did you find and correct a condition? | -- | Go to Step 15 | Go to Step 14 |
12 |
Did you find and correct a condition? | -- | Go to Step 15 | Go to Step 13 |
13 | Replace the MAF sensor. Refer to Mass Airflow Sensor Replacement . Did you complete the replacement? | -- | Go to Step 15 | -- |
14 | Replace the PCM. Refer to Powertrain Control Module Replacement . Did you complete the replacement? | -- | Go to Step 15 | -- |
15 |
Does the DTC run and pass? | -- | Go to Step 16 | Go to Step 2 |
16 | With a scan tool, observe the stored information, Capture Info. Does the scan tool display any DTCs that you have not diagnosed? | -- | System OK | |
