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 vehicle is a hot film meter (HFM) type. The engine control module (ECM) uses the MAF sensor signal in order to provide the correct fuel delivery for a wide range of engine speeds and loads. The MAF sensor signal is a function of the current required to keep the air flow sensing element at a fixed temperature. 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 in order to maintain the hot film at a constant temperature. The MAF sensor converts the changes in current to a voltage signal that is read by the ECM. The ECM calculates the air flow based on this voltage signal. The MAF sensor uses the following circuits in order to operate:
| • | The ignition 1 voltage |
| • | The 5-volt reference |
| • | The MAF sensor signal |
| • | The low reference |
The 5-volt reference for the MAF sensor is also supplied to additional sensors. For each of the sensors, the voltage is supplied on separate ECM terminals. The terminals are connected within the ECM to the same stabilized sensor supply voltage. The 5-volt reference is shared by the following sensors:
| • | The MAF sensor |
| • | The accelerator pedal position (APP) sensor 1 |
| • | The fuel tank pressure (FTP) sensor |
| • | The air conditioning (A/C) refrigerant pressure sensor |
The low reference circuit of the MAF sensor is shared with the following components:
| • | The camshaft position (CMP) sensor |
| • | The intake air temperature (IAT) sensor |
| • | The engine coolant temperature (ECT) sensor |
If the ECM detects the MAF sensor signal is less than the possible range of a properly operating sensor, DTC P0102 sets.
Conditions for Running the DTC
| • | The ECM has counted more than 20 crankshaft revolutions. |
| • | The engine speed is more than 300 RPM. |
| • | The engine has been running for more than 0.5 seconds in order to allow the MAF sensor hot film element to heat up. |
| • | The ignition 1 signal is more than 10 volts. |
Conditions for Setting the DTC
| • | The ECM detects that the MAF sensor signal is less than 0.42 volt for more than 2 seconds. |
| OR |
| • | The MAF sensor signal is less than a calculated value using throttle position (TP) and engine speed. |
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 for the following conditions: |
| - | A high resistance on any of the MAF sensor circuits except the low reference may cause this DTC to set intermittently and also result in poor engine performance. |
| - | A high resistance on the 5-volt reference of the MAF sensor may result in poor engine performance without setting this DTC. |
| - | A low minimum air rate through the sensor bore may cause this DTC to set at idle or during deceleration. Inspect for any vacuum leaks downstream of the MAF sensor. |
| - | Any contamination of the hot film element of the MAF sensor may cause this DTC to set. |
| - | A wide-open throttle acceleration from a stop should cause the MAF sensor g/s display on the scan tool to increase rapidly. This increase should be from 3-7 g/s at idle to 72 g/s or more at the time of the 1-2 shift. If the increase is not observed, inspect for a restriction in the Induction System or the Exhaust System. |
| • | If the condition is intermittent, refer to Intermittent Conditions . |
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-Engine Controls? | -- | Go to Step 2 | |||||||||||||||||||||
2 |
Important:: If you were sent here from DTC P0101, proceed to Step 3.
Does the DTC fail this ignition? | -- | Go to Step 3 | Go to Diagnostic Aids | ||||||||||||||||||||
3 | Inspect the fuse in the ignition 1 voltage circuit of the mass air flow (MAF) sensor. Is the fuse open? | -- | Go to Step 10 | Go to Step 4 | ||||||||||||||||||||
4 |
Did you find and correct the condition? | -- | Go to Step 20 | Go to Step 5 | ||||||||||||||||||||
5 |
Does the movement of the harness or the connector affect the MAF sensor g/s? | -- | Go to Step 15 | Go to Step 6 | ||||||||||||||||||||
6 |
Important:: DO NOT use the low reference circuit located in the MAF/IAT connector for this test. Engine control module (ECM) damage will result. Is the voltage within 0.50 volts of the specified value? | B+ | Go to Step 7 | Go to Step 14 | ||||||||||||||||||||
7 | Measure the voltage from the 5-volt reference circuit of the MAF sensor to a good ground with a DMM. Refer to Circuit Testing in Wiring Systems. Is the voltage within the specified range? | 4.8-5.2 V | Go to Step 8 | Go to Step 9 | ||||||||||||||||||||
8 |
Is the MAF sensor parameter more than the specified value? | 4.8 wV | Go to Step 16 | Go to Step 11 | ||||||||||||||||||||
9 | Is the voltage less than the specified value? | 5 V | Go to Step 12 | Go to Step 13 | ||||||||||||||||||||
10 |
Important:: The ignition 1 voltage circuit of the MAF sensor is spliced to other components of the vehicle. Test the ignition 1 voltage circuit of the MAF sensor for a short to ground. Refer to Circuit Testing , Testing for Short to Ground , and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 20 | -- | ||||||||||||||||||||
11 |
Did you find and correct the condition? | -- | Go to Step 20 | Go to Step 17 | ||||||||||||||||||||
12 |
Important: The 5-volt reference circuit is shared with other components of the vehicle.
Did you find and correct the condition? | -- | Go to Step 20 | Go to Step 17 | ||||||||||||||||||||
13 |
Important:: The 5-volt reference circuit is shared within the ECM with other components of the vehicle. Disconnecting the ECM may eliminate the short to voltage if the circuit is shorted to another ECM circuit. A short to voltage on the fuel tank pressure (FTP) sensor signal circuit will backfeed through the FTP sensor to the FTP 5-volt reference circuit.
Did you find and correct the condition? | -- | Go to Step 20 | Go to Step 17 | ||||||||||||||||||||
14 | Repair the high resistance or an open in the ignition 1 voltage circuit of the MAF sensor. Refer to Wiring Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 20 | -- | ||||||||||||||||||||
15 | Repair the harness or the connections as necessary. Refer to Wiring Repairs and Connector Repairs in Wiring Systems. Did you complete the repair? | -- | Go to Step 20 | -- | ||||||||||||||||||||
16 | Test for an intermittent and for a poor connection at the MAF sensor. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 20 | Go to Step 18 | ||||||||||||||||||||
17 | Test for an intermittent, a shorted or poor connection at the ECM. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 20 | Go to Step 19 | ||||||||||||||||||||
18 | Replace the MAF/IAT sensor. Refer to Mass Airflow Sensor/Intake Air Temperature Sensor Replacement . Did you complete the replacement? | -- | Go to Step 20 | -- | ||||||||||||||||||||
19 | Replace the ECM. Refer to Engine Control Module Replacement . Did you complete the replacement? | -- | Go to Step 20 | -- | ||||||||||||||||||||
20 |
Did the DTC fail this ignition? | -- | Go to Step 2 | Go to Step 21 | ||||||||||||||||||||
21 | Observe the Capture Info with a scan tool. Are there any DTCs that have not been diagnosed? | -- | System OK | |||||||||||||||||||||
