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 (Hz.) at idle to near 10,000 Hz. 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 more than the possible range of a correctly operating MAF sensor DTC P0103 sets.
DTC Descriptor
This diagnostic procedure supports the following DTC:
DTC P0103 Mass Air Flow (MAF) Sensor Circuit High Frequency
Conditions for Running the DTC
| • | The engine is running. |
| • | The Engine Speed parameter is more than 500 RPM. |
| • | This DTC runs continuously in a 12.5 ms loop. |
Conditions for Setting the DTC
The ECM detects that the MAF sensor frequency signal is more than 12,425 Hz for more than 200 ms.
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
| • | Inspect the air induction system for any water intrusion. The water rapidly cools the hot sensing elements in the sensor causing a false indication of excessive air flow. Any water that reaches the MAF sensor will skew the sensor and may cause this DTC to set. |
| • | A steady or intermittent high resistance in the 12-volt reference circuit of the MAF sensor will skew the MAF sensor frequency high and may cause this DTC to set. |
| • | If the condition is intermittent, refer to Inducing Intermittent Fault Conditions in Wiring Systems and Intermittent Conditions . |
Test Description
The numbers below refer to the step numbers on the diagnostic table.
-
This step tests for Electromagnetic Interference (EMI) on the signal circuit of the MAF sensor. A frequency reading with the MAF sensor disconnected may indicate an EMI related fault or a poor connection at the ECM. Disconnecting the MAF sensor may set additional related DTCs.
-
This step will determine if incorrect harness routing has caused this DTC to set.
-
This step will determine if water intrusion has caused this DTC to set.
-
This step will determine if a steady or intermittent high resistance at any point in the 12-volt reference circuit of the MAF sensor has caused this DTC to set.
Step | Action | Values | Yes | No | ||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
Schematic Reference: Engine Controls Schematics Connector End View Reference: Engine Controls Connector End Views or Engine Control Module Connector End Views | ||||||||||||||
1 | Did you perform the Diagnostic System Check-Vehicle? | -- | Go to Step 2 | Go to Diagnostic System Check - Vehicle in Vehicle DTC Information | ||||||||||
2 |
Did the DTC fail this ignition? | -- | Go to Step 3 | Go to Diagnostic Aids | ||||||||||
Is the MAF Sensor parameter more than the specified value? | 0 Hz | Go to Step 4 | Go to Step 5 | |||||||||||
Did you find and correct the condition? | -- | Go to Step 11 | Go to Step 8 | |||||||||||
Did you find and correct the condition? | -- | Go to Step 11 | Go to Step 6 | |||||||||||
Test the 12-volt reference circuit of the MAF sensor for the following conditions:
Refer to Inducing Intermittent Fault Conditions , Circuit Testing , Testing for Intermittent Conditions and Poor Connections , Wiring Repairs , and Connector Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 11 | Go to Step 7 | |||||||||||
7 | Test for an intermittent and for a poor connection at the MAF/IAT sensor. Refer to Testing for Intermittent Conditions and Poor Connections , Repairing Connector Terminals , and Connector Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 11 | Go to Step 9 | ||||||||||
8 | Test for an intermittent and for a poor connection at the ECM. Refer to Testing for Intermittent Conditions and Poor Connections , Repairing Connector Terminals , and Connector Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 11 | Go to Step 10 | ||||||||||
9 | Replace the MAF/IAT sensor. Refer to Mass Airflow Sensor Replacement . Did you complete the replacement? | -- | Go to Step 11 | -- | ||||||||||
10 | Replace the ECM. Refer to Engine Control Module Replacement . Did you complete the replacement? | -- | Go to Step 11 | -- | ||||||||||
11 |
Did the DTC fail this ignition? | -- | Go to Step 2 | Go to Step 12 | ||||||||||
12 | Observe the Capture Info with a scan tool. Are there any DTCs that have not been diagnosed? | -- | Go to Diagnostic Trouble Code (DTC) List - Vehicle in Vehicle DTC Information | System OK | ||||||||||
