| Table 1: | DTC P0100 - Mass Air Flow (MAF) Sensor Circuit |
Circuit Description
The Mass Air Flow (MAF) sensor measures the amount of air that is ingested by the engine. The direct measurement of air entering the engine is more accurate than calculating the airflow from the other sensor inputs. The MAF sensor has a switched battery feed, a ground, a signal circuit and a signal return circuit.
The MAF sensor used on this vehicle is a hot film type and is used to measure the air flow rate. The MAF output voltage is a function of the power required to keep the air flow sensing any elements at a fixed temperature above ambient temperature. The air flowing through the sensor cools the sensing elements. The amount of cooling is proportional to the amount of the air flow. As the air flow increases, a greater amount of current is required in order to maintain the hot film at a constant temperature. The MAF sensor converts the changes in current draw to a voltage signal read by the ECM. The ECM calculates the air flow based on this signal.
The ECM monitors the MAF sensor signal voltage and can determine if the sensor signal voltage is too low, too high, not indicating the expected airflow for a given operating condition, or that the signal appears to be stuck based on the lack of normal signal fluctuations expected during engine operation.
Conditions for Running the DTC
The engine speed is greater than 400 RPM.
OR
While cranking, the engine speed is greater than 120 RPM.
Conditions for Setting the DTC
The MAF signal indicates an airflow of less than 4 kg/h (1.111 g/s) or exceeds the maximum value for a given RPM as specified in the following table:
Engine Speed (RPM) | Mass Air Flow max. (g/s) |
|---|---|
1,000 | 23 |
2,000 | 32 |
3,000 | 39 |
4,000 | 50 |
5,000 | 62 |
6,000 | 70 |
The above conditions are present for at least 0.1 second.
Action Taken When the DTC Sets
| • | The ECM illuminates the malfunction indicator lamp (MIL) and records the operating conditions in the Freeze Frame on the second consecutive drive trip that the diagnostic runs and fails. |
| • | The ECM will calculate the airflow from the other sensor inputs. |
Conditions for Clearing the MIL/DTC
| • | The ECM turns OFF the MIL after three consecutive drive trips that the diagnostic runs and passes. |
| • | A History DTC clears after forty consecutive warm-up cycles in which no failures are reported by this diagnostic or any other emission related diagnostic. |
| • | The ECM battery voltage is interrupted. |
| • | The scan tool clears the MIL/DTC. |
Diagnostic Aids
Use the Connector Test Adapter Kit J 35616 for any test that requires probing the ECM harness connector or a component harness connector. Using this kit will prevent damage to the harness connector terminals.
Check for the following conditions:
| • | A plugged intake air duct or a dirty air filter element. |
| • | Poor connections at the ECM or at the component. Inspect the harness connectors for any of the following conditions: |
| - | Improper mating |
| - | Broken locks |
| - | Improperly formed or damaged terminals |
| - | A poor terminal to wire connection |
| - | Refer to Engine Control Module Diagnosis for the proper procedure. |
| • | A misrouted harness. Inspect the harness in order to ensure that the harness is not routed too close to the high voltage wires such as the spark plug leads, or too close to the high current devices such as the alternator, the motors, the solenoids etc. |
| • | A damaged harness. Inspect the wiring harness for damage. If the harness appears to be OK, observe the scan tool while moving the related connectors and the wiring harnesses. A change in the display may help in order to locate the fault. |
| If the sensor signal is only affected when the harness is moved near a component, and there is no problem with the harness or connections, the component may be damaged. |
Refer to Symptoms --Preliminary Checks for the intermittents.
Test Description
The number(s) below refer to the step numbers on the diagnostic table.
-
Monitoring the MAF sensor signal voltage will determine whether the fault is present now, or intermittent.
-
Using the Freeze Frame data may aid in locating an intermittent condition. If the DTC cannot be duplicated, review the information in the Freeze Frame. Try to operate the vehicle within the same freeze frame conditions (the RPM, the MAF, the vehicle speed, the temperature etc.) that were noted. This process may help to recreate the malfunction.
-
The scan tool display should go to the maximum value for this parameter (about 5 volts), although the actual voltage through the test light is higher.
Step | Action | Value(s) | Yes | No |
|---|---|---|---|---|
1 | Did you perform the Powertrain On-Board Diagnostic (OBD) System Check? | -- | ||
Turn on the ignition with the engine off. Is the MAF Voltage above the specified value? | 4.8 V | |||
3 |
Is the MAF Voltage below the specified value? | 0.2 V | ||
4 | Check for air leaks in the ductwork between the MAF sensor and the Throttle Body. Was a problem found and corrected? | -- | ||
5 | Move the harness and the related connectors while monitoring the MAF Voltage on the scan tool. Does the harness movement affect the MAF Voltage? | -- | ||
Is this DTC set? | -- | No trouble found. Refer to Diagnostic Aids | ||
7 | Disconnect the MAF sensor connector. Does the scan tool indicate the specified voltage? | 0V | ||
8 | Probe the ground circuit in the MAF sensor harness connector with the test light J 34142-B connected to B+. Does the test light illuminate? | -- | ||
9 | Probe the signal return circuit in the MAF sensor harness connector with the test light J 34142-B connected to B+. Does the test light illuminate? | -- | ||
10 |
Is continuity indicated? | -- | ||
11 |
Is there a voltage present? | -- | ||
Does the scan tool indicate the voltage shown? | 5.0V | |||
13 | Probe the MAF sensor B+ supply circuit in the MAF sensor harness connector with the test light J 34142-B connected to ground. Does the test light illuminate? | -- | ||
14 |
Is continuity indicated? | -- | ||
15 | Use the DVM J 39200 in order to check for continuity between the MAF sensor signal circuit and ground. Is continuity indicated? | -- | ||
16 | Repair the harness/connections as necessary. Refer to Test Description. Is the action complete? | -- | -- | |
17 | Repair the open/high resistance in the ground circuit. Is the repair completed? | -- | -- | |
18 | Repair open or high resistance in the signal return circuit. Is the repair completed? | -- | -- | |
19 | Repair the signal circuit that is shorted to voltage. Is the repair completed? | -- | -- | |
20 | Repair the open/high resistance in the switched B+ circuit. Is the repair completed? | -- | -- | |
21 | Repair the open/high resistance in the signal circuit. Is the repair completed? | -- | -- | |
22 | Repair the signal circuit shorted to ground. Is the repair completed? | -- | -- | |
23 | Check for a poor connection or poor terminal tension at the MAF sensor harness connector. Refer to Electrical Diagnosis in Engine Electrical, and Troubleshooting Procedures for the proper procedure. Also, refer to Checking Terminal Contact in Engine Control Module Diagnosis . Was a problem found and corrected? | -- | ||
24 | Replace the MAF sensor. Is the repair completed? | -- | -- | |
25 | Check for a poor connection or poor terminal tension at the ECM harness connector. Refer to Electrical Diagnosis in Engine Electrical, and Troubleshooting Procedures for the proper procedure.Also, refer to Checking Terminal Contact in Engine Control Module Diagnosis . Was a problem found and corrected? | -- | ||
26 |
Important: This vehicle is equipped with a Theft Deterrent System which interfaces with the Engine Control Module (ECM). Program the new ECM with the frequency code of the theft deterrent module that is currently on the vehicle. Replace the ECM. Refer to Engine Control Module Replacement/Programming . Is the action complete? | -- | -- | |
27 |
Is this DTC set? | -- | ||
28 | Were there any additional DTCs noted during the Powertrain OBD System Check that have not been diagnosed? | -- | Go to the applicable DTC table | The System is OK |
