Circuit Description
The mass air flow (MAF) sensor is an air flow meter that measures the amount of air entering the engine. The engine control module (ECM) uses the MAF sensor voltage signal in order to provide the correct fuel delivery for a reduction in emissions. The ECM uses the MAF sensor signal in order to control fuel delivery until a calibrated amount of engine air flow is attained. The MAF sensor has an ignition 1 voltage circuit, a signal circuit and a low reference circuit. The MAF sensor produces an output voltage based on inlet air flow through the air induction system. This output voltage will display on the scan tool as a grams per second (g/s) value. Diagnostic trouble code (DTC) P0103 will set if the actual MAF sensor voltage signal is more than the possible range of a normally operating sensor.
Conditions for Running the DTC
| • | The engine is running for more than 2 seconds. |
| • | The engine speed is more than 500 RPM. |
| • | The ignition 1 signal is more than 9 volts. |
| • | The above conditions are present for more than 2 seconds. |
Conditions for Setting the DTC
| • | The ECM detects that the MAF sensor signal is more than 4.8 volts. This equals a MAF value of more than 490 g/s. |
| • | The condition is present for more than 2 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 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 sluggish or unresponsive MAF sensor. A short between the signal circuit of the MAF sensor and the signal circuit of the intake air temperature (IAT) sensor. This will cause the MAF sensor to have a very limited output voltage range. |
| • | Any water in the air induction system. |
| • | If the condition is intermittent, refer to Intermittent Conditions . |
Step | Action | Values | Yes | No |
|---|---|---|---|---|
Schematic Reference: Engine Controls Schematics | ||||
1 | Did you perform the Diagnostic System Check-Engine Controls? | -- | Go to Step 2 | |
2 |
Does the scan tool display any other DTCs set? | -- | Go to Step 3 | |
3 |
Does the DTC fail this ignition? | -- | Go to Step 4 | Go to Diagnostic Aids |
4 |
Does the movement of the harness or the connector affect the MAF sensor g/s? | -- | Go to Step 13 | Go to Step 5 |
5 |
Is the MAF sensor g/s more than the specified value? | 444 g/s | Go to Step 8 | Go to Step 6 |
6 |
Does the test lamp illuminate? | -- | Go to Step 14 | Go to Step 7 |
7 |
Does the DMM indicate good continuity? | -- | Go to Step 15 | Go to Step 10 |
8 |
Important:: Disconnecting the harness connectors of the ECM may eliminate the short to voltage if the signal circuit is shorted to another ECM circuit.
Does the DMM indicate a short to voltage? | -- | Go to Step 11 | Go to Step 9 |
9 | Use a DMM in order to test for continuity at the harness connector of the ECM from the signal circuit of the MAF sensor to all other circuits at both ECM connectors. Refer to Circuit Testing in Wiring Systems. Does the DMM indicate continuity between any other circuit? | -- | Go to Step 12 | Go to Step 15 |
10 | Repair the high resistance or an open in the low reference circuit of the MAF sensor. Refer to Wiring Repairs in Wiring Systems. Did you complete the repair? | -- | Go to Step 18 | -- |
11 | Repair the short to voltage in the signal circuit of the MAF sensor. Refer to Wiring Repairs in Wiring Systems. Did you complete the repair? | -- | Go to Step 18 | -- |
12 | Repair the circuits that are shorted together. Refer to Wiring Repairs in Wiring Systems Did you complete the repair? | -- | Go to Step 18 | -- |
13 | Repair the harness or the connections as necessary. Refer to Circuit Testing in Wiring systems. Did you complete the repair? | -- | Go to Step 18 | -- |
14 | Inspect for poor connections at the harness connector of the MAF sensor. Refer to Connector Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 18 | Go to Step 16 |
15 | Inspect for poor connections at the harness connector of the ECM. Refer to Connector Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 18 | Go to Step 17 |
16 | Replace the MAF/IAT sensor. Refer to Mass Airflow Sensor/Intake Air Temperature Sensor Replacement Did you complete the replacement? | -- | Go to Step 18 | -- |
17 | Replace the ECM. Refer to Engine Control Module Replacement Did you complete the replacement? | -- | Go to Step 18 | -- |
18 |
Does the DTC run and pass? | -- | Go to Step 19 | Go to Step 2 |
19 | With a scan tool, observe the stored information, Capture Info. Does the scan tool display any DTCs that you have not diagnosed? | -- | System OK | |
