For 1990-2009 cars

### Circuit Description

The DTC P0102 Mass Air Flow (MAF) Sensor Circuit Low Voltage diagnostic monitors the MAF sensor signal. The MAF sensor measures the amount of air which passes through the sensor in a given amount of time. The powertrain control module (PCM) uses this information to determine the operating requirements of the engine in order to control the fuel delivery. The PCM calculates the engine's fuel requirements by monitoring the current flow on the signal wire from the MAF sensor. When the volume of air entering the MAF sensor increases, the current flow seen by the PCM from the MAF sensor also increases. When the air flow decreases, the current seen by the PCM also decreases. The MAF sensor is located between the air intake tube and the air cleaner in the right front area of the engine compartment.

### Conditions for Running the DTC

The ignition key is On or the engine is running.

### Conditions for Setting the DTC

• | The MAF sensor output current is less than 0.64 mA

• | The condition is present for more than 5 seconds

### Action Taken When the DTC Sets

• | The PCM illuminates the malfunction indicator lamp (MIL).

• | The PCM records the operating conditions at the time the diagnostic fails. This information is stored in the Freeze Frame buffer.

• | The PCM enters the Fail-safe mode and determines the injector drive time and the idle air control (IAC) duty cycle according to the throttle position (TP) sensor input and the engine speed.

### Conditions for Clearing the MIL/DTC

• | The PCM turns OFF the MIL after 3 consecutive trips without a fault.

• | The PCM clears a history DTC after 40 consecutive warm-up cycles without a fault.

• | Perform the scan tool clear DTC Information function in order to clear the DTC.

### Diagnostic Aids

Check for any of the following conditions:

• | A misrouted wiring harness. Inspect the MAF sensor harness to ensure that the harness is not routed too close to high voltage wires such as spark plug leads.

• | A damaged wiring harness. Inspect the wiring harness for damage. If the harness appears to be OK, observe the scan tool while moving the connectors and the wiring harnesses related to the MAF sensor. A change in the display will indicate the location of the fault.

• | Check for an air intake restriction. An acceleration from a stop should cause the MAF sensor parameter displayed on a scan tool to increase from about 2 to 3.5 g/s at idle to 5 to 9 g/s at 2,000 RPM. Check for a plugged intake air duct or dirty air filter element.

If a DTC P0102 is intermittent, driving the vehicle under the following conditions can verify whether the fault is present. Perform the scan tool clear DTC information function. Road test the vehicle while monitoring the DTC P0102 diagnostic on the scan tool under the Not Ran Since Code Cleared selection in the DTC Information menu. If a DTC P0102 appears in the Not Ran Since Code Cleared list, the P0102 diagnostic has not yet run. When the DTC P0102 does not appear in the Not Ran Since Code Cleared list, the P0102 diagnostic has run. If the MIL is NOT illuminated, and there is no Pending DTC Status in DTC Information, the P0102 diagnostic has passed. The DTCs MUST be cleared in order to view the Current Status of the Not Ran Since Code Cleared list. The Not Ran Since Code Cleared list only indicates whether or not the test has run, not whether the test passed or failed. The DTC Information screen must be checked for Current or Pending status, in order to determine the outcome of the diagnostic test involved.

An intermittent malfunction may be caused by a fault in the MAF sensor circuit. Inspect the wiring harness and components for an intermittent condition. Refer to Intermittent Conditions .

If the DTC P0102 cannot be duplicated, the information included in the Freeze Frame data can be useful in determining the vehicle operating conditions when the DTC was first set.

### Test Description

The numbers below refer to the step numbers in the diagnostic table.

1. The Diagnostic System Check-Engine Controls prompts the technician to complete some basic checks and store the freeze frame data on the scan tool if applicable. This creates an electronic copy of the data taken when the fault occurred. The information is then stored in the scan tool for later reference.

2. This step will determine if the fault is present.

3. Review the Freeze Frame data to determine when the DTC set. Always record this information.

4. This step checks for an open or a short in the MAF sensor signal circuit between the MAF sensor and the PCM.

5. Clearing the DTCs by removing the DOME fuse also clears the PCM long term memory. Using the scan tool to clear DTCs leaves the long term memory active. DTC emitting diagnostics may not run to completion as expected unless the long term memory is cleared. Removal of the DOME fuse also clears the time display of the radio. The DTC P0102 diagnostic can be monitored on the scan tool under the Not Ran Since Code Cleared selection in the DTC Information menu. If a DTC P0102 appears in the Not Ran Since Code Cleared list, the DTC P0102 diagnostic has not yet run. When the DTC P0102 does not appear in the Not Ran Since Code Cleared list, the DTC P0102 diagnostic has run. If the MIL is NOT illuminated, and there is no Pending DTC Status in DTC Information, the DTC P0102 diagnostic has passed. The DTCs MUST be cleared in order to view the Current Status of the Not Ran Since Code Cleared list. The Not Ran Since Code Cleared list only indicates whether or not the test has run, not whether the test passed or failed. The DTC Information screen must be checked for Current or Pending status, in order to determine the outcome of the diagnostic test involved.

Step | Action | Value(s) | Yes | No
--- | --- | --- | --- | ---
Schematic Reference: Engine Controls Schematics
1 | Did you perform the Diagnostic System Check-Engine Controls? | -- | Go to Step 2 | Go to Diagnostic System Check - Engine Controls
2 |

1. Start the engine.
2. Install a scan tool.
3. With the throttle closed, select the mass air flow (MAF) sensor parameter on the scan tool.

Is the MAF within the specified range?

2.0--4.0 g/s

Go to Step 3

Go to Step 4

3 |

1. Turn ON the ignition, leaving the engine off.
2. Perform the scan tool Clear DTC Information function.
3. Operate the vehicle within the Freeze Frame conditions as specified.

Does this DTC set?

--

Go to Step 4

Go to Diagnostic Aids

4 |

1. Turn OFF the ignition.
2. Disconnect the MAF sensor connector.
3. Turn ON the ignition, leaving the engine off.
4. Measure the voltage from the MAF sensor ignition feed circuit using a digital multimeter (DMM) connected to ground.

Is the voltage near the specified value?

B+

Go to Step 5

Go to Step 6

5 |

1. Turn OFF the ignition.
2. Reconnect the MAF sensor connector.
3. Turn ON the ignition, leaving the engine off.
4. Backprobe the MAF sensor signal circuit at PCM using a DMM.
5. Measure the voltage.

Is the voltage within the specified range?

1.0-1.6 V

Go to Step 9

Go to Step 7

6 | Repair the open or the short circuit in the MAF sensor ignition feed circuit. Refer to Wiring Repairs in Wiring Systems. Is the action complete? | -- | Go to Step 10 | --
7 |

1. Check the MAF sensor signal circuit for the following conditions:

• | An open between the PCM and the MAF sensor.

• | A short between the PCM and the MAF sensor.

• | A poor connection at the MAF sensor. Refer to Testing for Intermittent Conditions and Poor Connections in Wiring Systems.

2. Repair as necessary. Refer to Wiring Repairs in Wiring Systems.

Was a repair necessary?

--

Go to Step 10

Go to Step 8

8 | Replace the MAF sensor. Refer to Mass Airflow Sensor Replacement . Is the action complete? | -- | Go to Step 10 | --
9 | Replace the PCM. Refer to Powertrain Control Module Replacement . Is the action complete? | -- | Go to Step 10 | --
10 |

1. Turn OFF the ignition.
2. Remove the DOME fuse for 30 seconds.
3. Install the DOME fuse.
4. Reset the radio clock time. Refer to Radio/Audio System Description and Operation in Entertainment.
5. Start the engine.
6. Operate the vehicle within the Conditions for Running the DTC as specified in the supporting text or until the DTC P0102 diagnostic test has run.

Does the DTC run and pass?

--

Go to Step 11

Go to Step 2

11 | With a scan tool, observe the stored information, Capture Info. Does the scan tool display any DTCs that you have not diagnosed? | -- | Go to Diagnostic Trouble Code (DTC) List | System OK