For 1990-2009 cars
Engine Controls Components
MAF Sensor, EVAP System, EGR Valve
OBD II Symbol Description Notice
Handling ESD Sensitive Parts Notice

### Circuit Description

The Mass Air Flow (MAF) sensor measures the amount of air which passes through it into the engine during a given time. The PCM uses the mass air flow information to monitor engine operating conditions for fuel delivery calculations. A large quantity of air entering the engine indicates an acceleration or high load situation, while a small quantity of air indicates deceleration or idle. The MAF sensor produces a frequency signal which can be monitored using a scan tool. The frequency will vary within a range of around 2000 Hertz at idle to about 10,000 Hertz at maximum engine load. DTC P0101 will be set if the signal from the MAF sensor does not match a predicted value based on barometric pressure (calculated from MAP at key ON), throttle position, and engine RPM.

### Conditions for Running the DTC

• | The engine is running.

• | System voltage is between 9V and 18V.

• | The throttle is steady.

• | EGR duty cycle is less than 100%.

• | MAP is less than 80 kPa.

• | EVAP Canister Purge less than 100%.

### Conditions for Setting the DTC

MAF signal frequency indicates an airflow significantly higher or lower than a predicted value. The value is based on barometric pressure, throttle position, intake air temperature, engine coolant, and engine RPM.

### Action Taken When the DTC Sets

• | The PCM will illuminate the malfunction indicator lamp (MIL) during the first trip in which the diagnostic test has been run and failed.

• | The PCM will store conditions which were present when the DTC set as Freeze Frame and Failure Records data.

### Conditions for Clearing the MIL/DTC

• | The PCM will turn OFF the MIL during the third consecutive trip in which the diagnostic has been run and passed.

• | The History DTC will clear after 40 consecutive warm-up cycles have occurred without a malfunction.

• | The DTC can be cleared by using the scan tool.

### Diagnostic Aids

Check for the following conditions:

• | Poor connection at the PCM - Inspect harness connectors for the following conditions:

- | Backed out terminals.

- | Improper mating.

- | Broken locks.

- | Improperly formed or damaged terminals.

- | Poor terminal to wire connection.

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

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

• | Plugged intake air duct or dirty air filter element - A wide-open throttle acceleration from a stop should cause the Mass Air Flow displayed on a scan tool to increase from about 4-7 gm/s at idle to 100 gm/s or greater at the time of the 1-2 shift. If not, check for a restriction.

• | Skewed or unresponsive MAP sensor - The barometric pressure used to calculate the default Mass Air Flow value is based on the MAP sensor reading. A skewed MAP sensor at key ON will cause the BARO reading to be incorrectly calculated. Also, with the engine running, an unresponsive MAP sensor (due to poor vacuum connections, damaged vacuum source, or defective vacuum hose(s), unmetered air into the manifold) will cause inaccurate BARO reading updates during wide-open throttle conditions. Both of these conditions result in a difference between the actual MAF sensor signal and the predicted MAF value (PCM calculated). If a large difference between these two values occurs DTC P0101 will set.

• | Skewed Cam Sensor Signal - intermittently shorted to ground, causing a fluctuation in RPM as seen on the scan tool.

If DTC P0101 cannot be duplicated, the information included in the Freeze Frame/Fail Records data can be useful in determining vehicle mileage since the DTC was last set. This may assist in determining how often the DTC sets.

### Test Description

Number(s) below refer to the Step number(s) on the Diagnostic Table:

1. This step verifies that the problem is present.

2. This step verifies a proper MAP/BARO value at initial key ON. If the MAP sensor is stuck the barometric pressure value will be incorrectly calculated. This will cause the predicted Mass Air Flow calculations to be inaccurate. DTC P0101 will set if the MAF sensor signal does not match the predicted MAF value.

3. This step verifies a proper MAP sensor signal with engine running. With a closed throttle and proper engine vacuum, the MAP sensor signal should be between 29 kPa and 48 kPa.

4. This step verifies a proper MAP sensor response as the throttle is opened. As the throttle is steadily opened, pressure in the intake manifold increases. The MAP sensor signal should increase steady as the pressure increases.

5. Tests for conditions which can cause a good MAF sensor to appear faulty.

6. A voltage reading of less than 4 or greater than 6 volts at the MAF sensor signal circuit indicates a fault in the wiring or a poor connection.

7. Verifies that ignition feed voltage and a good ground are available at the MAF sensor.

8. This vehicle is equipped with a PCM which utilizes an Electrically Erasable Programmable Read Only Memory (EEPROM). When the PCM is replaced, the new PCM must be programmed.

#### DTC P0101 - Mass Air Flow System Performance

Step | Action | Value(s) | Yes | No
--- | --- | --- | --- | ---
1 | Did you perform the Powertrain On-Board Diagnostic (OBD) System Check performed? | -- | Go to Step 2 | Go to Powertrain On Board Diagnostic (OBD) System Check
2 | Are any other DTCs set other than P1514? | -- | Go to applicable DTCs | Go to Step 3
3 |

1. Turn ON the ignition, with the engine OFF.
2. With a scan tool, review and record Fail Records.
3. Operate vehicle within Fail Records conditions.

Does the scan tool indicate this DTC failed this ignition?

--

Go to Step 4

Go to Diagnostic Aids

4 |

1. Turn ON the ignition.
2. With a scan tool, observe the MAP and BARO parameters.

Does the scan tool indicate MAP and BARO within the specified range?

65-105 kPa

Go to Step 5

Go to Step 8

5 |

1. Start the engine.
2. With a scan tool, observe the MAP sensor parameter, with the engine idling.

Does the scan tool indicate MAP within the specified range?

29-48 kPa

Go to Step 6

Go to Step 7

6 | With a scan tool, observe the MAP sensor Parameter, while slowly increasing engine speed to 3000 RPM. Does the MAP sensor value increase as engine speed increases? | -- | Go to Step 9 | Go to Step 8
7 | Inspect for the following conditions:

1. Objects blocking the throttle body inlet screen.
2. Intake manifold vacuum leaks.
3. Vacuum leaks at throttle body.
4. Vacuum leaks at EGR valve
5. PCV valve faulty, missing, or incorrectly installed.
6. Skewed or unresponsive MAP Sensor. Refer to DTC P0101 Diagnostic Aids.

Did you find and correct the condition?

--

Go to Step 21

Go to Step 9

8 | Replace the MAP sensor. Refer to Manifold Absolute Pressure Sensor Replacement . Did you complete the replacement? | -- | Go to Step 21 | --
9 |

1. Turn OFF the ignition.
2. Disconnect the MAF sensor.
3. Turn ON the ignition.
4. Measure the voltage on the MAF signal circuit using a J 39200 Digital Multimeter that is connected to a good ground.

Does the voltage measure near the specified value?

5V

Go to Step 10

Go to Step 11

10 | Connect a J 35616-200 Test Lamp between the MAF sensor ignition feed and ground circuits. Does the test lamp illuminate? | -- | Go to Step 14 | Go to Step 13
11 | Is the voltage less than the specified value? | 4.5V | Go to Step 15 | Go to Step 12
12 |

1. Turn OFF the ignition.
2. Disconnect the PCM.
3. Turn ON the ignition.
4. Measure the voltage on the MAF signal circuit using a DMM that is connected to a good ground.

Does the voltage measure at or near the specified value?

0V

Go to Step 20

Go to Step 18

13 | Probe the MAF sensor ignition feed circuit using a test lamp that is connected to a good ground. Does the test lamp illuminate? | -- | Go to Step 16 | Go to Step 17
14 | Inspect for a poor connection at the MAF sensor. Refer to Intermittents and Poor Connections Diagnosis and Connector Repairs . Did you find and correct the condition? | -- | Go to Step 21 | Go to Step 19
15 |

1. Test the MAF signal circuit for the following conditions:

• | Open between the PCM and the MAF sensor.

• | Shorted to ground.

• | Poor connection at the PCM.

• | Shorted to the MAF sensor ground circuit.

2. If a problem is found, repair as necessary. Refer to Intermittents and Poor Connections Diagnosis , Wiring Repairs and Connector Repairs .

Did you find and correct the condition?

--

Go to Step 21

Go to Step 20

16 | Locate and repair the open in the MAF sensor ground circuit. Refer to Wiring Repairs . Did you complete the repair? | -- | Go to Step 21 | --
17 | Locate and repair the open in the MAF sensor ignition feed circuit. Refer to Wiring Repairs . Did you complete the repair? | -- | Go to Step 21 | --
18 | Locate and repair the short to voltage in the MAF sensor signal circuit. Refer to Wiring Repairs . Did you complete the repair? | -- | Go to Step 21 | --
19 | Replace the MAF sensor. Refer to Mass Airflow Sensor Replacement . Did you complete the replacement? | -- | Go to Step 21 | --
20 | Important:: The replacement PCM must be programmed. Refer to Powertrain Control Module Replacement/Programming . Replace the PCM. Did you complete the replacement? | -- | Go to Step 21 | --
21 |

1. Use the scan tool in order to clear DTCs.
2. Operate the vehicle within the Fail Record conditions.

Does the DTC reset?

--

Go to Step 2

System OK