Circuit Description
The mass air flow (MAF) sensor is located in the air intake duct. The MAF sensor is an airflow meter that measures the amount of air that enters the engine. The MAF sensor uses a hot film that is cooled by air flowing past the sensing film as air enters the engine. The amount of cooling is proportional to the amount of the air flow. As the air flow increases, more current is required in order to maintain the hot film at a constant temperature. The engine control module (ECM) uses the MAF sensor in order to provide the correct fuel delivery for all operating conditions. The MAF sensor uses the following circuits in order to operate:
| • | An ignition 1 voltage circuit |
| • | A 5-volt reference circuit |
| • | A low reference circuit |
| • | A signal circuit |
The ECM monitors the following inputs in order to calculate a predicted MAF sensor value:
| • | The intake air temperature (IAT) |
| • | The engine coolant temperature (ECT) |
| • | The throttle position (TP) |
| • | The engine speed |
The ECM monitors the MAF sensor signal for being stuck in range, for being too low, or for being too high for a given operating condition. If the ECM detects a MAF sensor signal voltage that is too high, this DTC sets.
DTC Descriptor
This diagnostic procedure supports the following DTC:
DTC P0103 Mass Air Flow (MAF) Sensor Circuit High Voltage
Conditions for Running the DTC
| • | Before the ECM can report DTC P0103 failed, DTCs P0121, P0122, P0123, P0221, P0222, P0223, P0336, and P0338 must run and pass. |
| • | The engine is operating. |
| • | The ignition 1 voltage is more than 7.5 volts. |
| • | DTC P0103 runs continuously once the above conditions are met for less than 1 second. |
Conditions for Setting the DTC
| • | The ECM detects that the MAF sensor signal is more than 294 grams per second. |
| • | The condition exists for more than 4 seconds. |
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 4 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
The following table illustrates the ECM connector locations:
ECM Connector Location | |
|---|---|
C2 | C1 |
Front of Vehicle | |
| • | Use the J 35616-A/BT-8637 GM Approved Terminal Test Kit for any test that requires probing the ECM harness connector or a component harness connector. |
| • | Inspect for mis-routed harnesses. Inspect the MAF sensor harness for routing that is too close to the following components: |
| - | Ignition coils |
| - | Solenoids |
| - | Relays |
| - | Motors |
| • | For an intermittent condition, refer to Intermittent Conditions . |
Test Description
The numbers below refer to the step numbers on the diagnostic table.
-
This step tests the signal circuit of the MAF sensor for a short to voltage.
-
This step tests for high resistance in the low reference circuit of the MAF/IAT sensor. The MAF sensor and the IAT sensor share the low reference circuit. If there is a condition with the low reference circuit, a MAF and IAT sensor DTC may set. The ECM must be completely powered down to obtain an accurate resistance reading. It may take up to 30 minutes for the ECM to power down after the ignition key is removed. Removal of the ECM fuse, or the PCM/ETC fuse, allows the ECM to power down completely.
-
This step tests the low reference circuit for a short to voltage. The control module or the sensor may be damaged if the circuit is shorted to battery voltage. Ensure that a short to voltage is repaired before replacing any components.
-
Inspect the MAF/IAT sensor connector for water intrusion, corrosion, and bent or damaged terminals.
-
Inspect the ECM connectors for water intrusion, corrosion, and bent or damaged terminals.
Step | Action | Values | Yes | No |
|---|---|---|---|---|
Schematic Reference: Engine Controls Schematics Connector End View Reference: Engine Control Module Connector End Views or Engine Controls Connector End Views | ||||
1 | Did you perform the Diagnostic System Check - Vehicle? | -- | Go to Step 2 | |
2 |
Does the parameter display less than the specified value? | 290 g/s | Go to Step 3 | Go to Step 4 |
3 |
Did the DTC fail this ignition? | -- | Go to Step 4 | Go to Diagnostic Aids |
Does the parameter display less than the specified value? | 4 V | Go to Step 5 | Go to Step 7 | |
Notice: Do NOT use a test lamp to test the continuity of the circuit. Damage to the control module may occur due to excessive current draw. Is the resistance less than the specified value? | 5 ohms | Go to Step 9 | Go to Step 6 | |
Is the voltage less than the specified value? | 1 V | Go to Step 8 | Go to Step 11 | |
7 |
Important: The control module or the sensor may be damaged if the circuit is shorted to battery positive voltage.
Did you find and correct the condition? | -- | Go to Step 14 | Go to Step 10 |
8 | Test the low reference circuit of the MAF/IAT sensor for an open or a high resistance. Refer to Circuit Testing and Wiring Repairs . Did you find and correct the condition? | -- | Go to Step 14 | Go to Step 10 |
Test for shorted terminals and poor connections at the MAF/IAT sensor. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs . Did you find and correct the condition? | -- | Go to Step 14 | Go to Step 12 | |
Test for shorted terminals and poor connections at the ECM. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs . Did you find and correct the condition? | -- | Go to Step 14 | Go to Step 13 | |
11 |
Important: The control module or the sensor may be damaged if the circuit is shorted to battery positive voltage. Repair the short to voltage in the low reference circuit of the MAF/IAT sensor. Refer to Wiring Repairs . Did you complete the repair? | -- | Go to Step 14 | -- |
12 | Replace the MAF sensor. Refer to Mass Airflow Sensor/Intake Air Temperature Sensor Replacement . Did you complete the replacement? | -- | Go to Step 14 | -- |
13 | Replace the ECM. Refer to Control Module References for replacement, setup, and programming. Did you complete the replacement? | -- | Go to Step 14 | -- |
14 |
Did the DTC fail this ignition? | -- | Go to Step 2 | Go to Step 15 |
15 | Observe the Capture Info with a scan tool. Are there any DTCs that have not been diagnosed? | -- | System OK | |
