Diagnostic Instructions
| • | Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure. |
| • | Review Strategy Based Diagnosis for an overview of the diagnostic approach. |
| • | Diagnostic Procedure Instructions provides an overview of each diagnostic category. |
DTC Descriptors
DTC P0102: Mass Air Flow (MAF) Sensor Circuit Low FrequencyDTC P0103: Mass Air Flow (MAF) Sensor Circuit High Frequency
Diagnostic Fault Information
Circuit | Short to Ground | High Resistance | Open | Short to Voltage | Signal Performance |
|---|---|---|---|---|---|
Ignition 1 Voltage | P0102 | P0101 | P0102 | -- | P0101, P0103 |
MAF Sensor Signal | P0102 | P0102 | P0102 | P0102 | P0101, P0103, P1101 |
Ground | -- | P0102 | P0102 | -- | P0102 |
Typical Scan Tool Data
Circuit | Normal Range | Short to Ground | Open | Short to Voltage |
|---|---|---|---|---|
Ignition 1 Voltage | -- | 0 Hz | 0 Hz | -- |
MAF Sensor Signal | 1,700-9,500 Hz | 0 Hz | 0 Hz | 0 Hz |
Ground | -- | -- | 0 Hz | -- |
Circuit/System Description
The mass air flow (MAF) sensor is integrated with the intake air temperature (IAT) sensor. The 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 signal to provide the correct fuel delivery for all engine speeds and loads. A small quantity of air entering the engine indicates a deceleration or idle condition. A large quantity of air entering the engine indicates an acceleration or high load condition. The MAF/IAT sensor has the following circuits:
| • | An ignition 1 voltage circuit |
| • | A ground circuit |
| • | A MAF sensor signal circuit |
| • | An IAT sensor signal circuit |
| • | A low reference circuit |
The ECM applies 5 volts to the MAF sensor on the MAF sensor signal circuit. The sensor uses the voltage to produce a frequency based on the inlet air flow through the sensor bore. The frequency varies in a range of near 1,700 Hertz at idle to near 9,500 Hertz at maximum engine load.
Conditions for Running the DTC
| • | The engine is running for greater than one second. |
| • | The engine speed is greater than 300 RPM. |
| • | The ignition 1 signal is greater than 8 volts. |
| • | The above conditions are met for greater than 1 second. |
| • | This DTC runs continuously within the enabling conditions. |
Conditions for Setting the DTC
P0102
The ECM detects that the MAF Sensor parameter is less than 10 Hz for greater than 5 seconds.
P0103
The ECM detects that the MAF Sensor parameter is greater than 11,000 Hz for greater than 5 seconds.
Action Taken When the DTC Sets
| • | DTC P0102 is a Type B DTC. |
| • | DTC P0103 is a Type B DTC. |
Conditions for Clearing the MIL/DTC
| • | DTC P0102 is a Type B DTC. |
| • | DTC P0103 is a Type B DTC. |
Diagnostic Aids
| • | A steady or intermittent high resistance of 15 ohms or greater on the ignition 1 voltage circuit will cause the MAF sensor signal to be increased by as much as 60 g/s. A slightly greater resistance can cause the signal to cease. To pinpoint this condition perform a voltage drop test on the circuit. |
| • | Any type of contamination on the MAF sensor heating elements will degrade the proper operation of the sensor. Certain types of contaminants act as a heat insulator, which will impair the response of the sensor to airflow changes. Water or snow can create the opposite effect, and cause the signal to increase rapidly. |
| • | Depending on the current ambient temperature, and the vehicle operating conditions, a MAF sensor signal circuit that is shorted to the IAT signal circuit will increase or decrease the MAF sensor signal that is interpreted by the ECM. Additionally it may cause a rapid fluctuation in the IAT Sensor parameter. |
Reference Information
Schematic Reference
Connector End View Reference
Electrical Information Reference
DTC Type Reference
Powertrain Diagnostic Trouble Code (DTC) Type Definitions
Scan Tool Reference
Special Tools Required
J 38522 Variable Signal Generator
Circuit/System Verification
| • | Verify the integrity of the air induction system by inspecting for the following conditions: |
| - | Damaged components |
| - | Loose or improper installation |
| - | An air flow restriction |
| - | Any vacuum leak |
| - | Water intrusion |
| • | Engine Running, observe the scan tool MAF Sensor parameter. The reading should be between 1,700-3,200 Hz depending on the engine coolant temperature (ECT). |
| • | A wide open throttle (WOT) acceleration from a stop should cause the MAF sensor parameter on the scan tool to increase rapidly. This increase should be from 2-6 g/s at idle to greater than 100 g/s at the time of the 1-2 shift. |
| • | Verify that any electrical aftermarket devices are properly connected and grounded. Refer to Checking Aftermarket Accessories . |
Circuit/System Testing
- Ignition OFF, disconnect the MAF/IAT harness connector at the MAF/IAT sensor.
- Ignition OFF, test for less than 5.0 ohms of resistance between the ground circuit terminal B and ground.
- Ignition ON, verify that a test lamp illuminates between the ignition circuit terminal C and ground.
- Ignition ON, test for 4.8-5.2 volts between the signal circuit terminal A and ground.
- Connect the J 38522 to the vehicle. Refer to Component Testing for instructions.
Important: All electrical components and accessories must be turned OFF, and allowed to power down.
| ⇒ | If greater than the specified range, test the ground circuit for an open/high resistance. |
| ⇒ | If the test lamp does not illuminate, test the ignition circuit for a short to ground or an open/high resistance. |
| ⇒ | If less than the specified range, test the signal circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the ECM. |
| ⇒ | If greater than the specified range, test the signal circuit for a short to voltage. If the circuit tests normal, replace the ECM. |
Component Testing
To determine if the ECM can properly process the MAF sensor frequency signal, connect the J 38522 to the vehicle as follows:
- Turn OFF the ignition.
- Connect the battery voltage supply, and ground the black lead.
- Connect the red lead to the signal circuit of the MAF sensor.
- Set the Duty Cycle switch to Normal.
- Set the Frequency switch to 5 K.
- Set the Signal switch to 5 V.
- Start the engine.
- Observe the MAF Sensor parameter for the correct range of 4,950-5,025 Hz.
| ⇒ | If the MAF Sensor parameter is not within the specified range, replace the ECM. |
| ⇒ | If the MAF Sensor parameter is within the specified range, replace the MAF sensor. |
Repair Instructions
Perform the Diagnostic Repair Verification after completing the diagnostic procedure.
| • | Control Module References for ECM replacement, setup, and programming |
