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For 1990-2009 cars only
Makes 🢒 Cadillac 🢒 2005 🢒 XLR 🢒 Engine 🢒 Engine Controls - 4.6L (LH2) 🢒 DTC P0102

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 engine is a hot film meter (HFM) type. The engine control module (ECM) applies a voltage to the sensor on the signal circuit. The sensor uses the voltage to produce a frequency based on the inlet air flow through the sensor bore. The frequency varies within a range of near 2,500 Hz at idle to near 10,000 Hz at maximum engine load. The MAF sensor frequency signal is a function of the current required to keep the air flow sensing element at a fixed temperature above ambient. 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 to maintain the hot film at a constant temperature. The ECM uses the MAF sensor signal to provide the correct fuel delivery for a wide range of engine speeds and loads. The MAF sensor uses the following circuits to operate:

    • A 12-volt reference circuit
    • A low reference circuit that is shared with the intake air temperature (IAT) sensor
    • A signal circuit

The 12-volt reference circuit of the MAF sensor is also supplied to additional sensors and they are connected within the ECM. The 12-volt reference is shared by the following sensors:

    • The MAF sensor
    • The crankshaft position (CKP) sensor
    • The camshaft position (CMP) sensor bank 1 intake
    • The CMP sensor bank 1 exhaust
    • The CMP sensor bank 2 intake
    • The CMP sensor bank 2 exhaust

If the ECM detects the frequency signal is less than the possible range of a correctly operating MAF sensor DTC P0102 sets.

DTC Descriptor

This diagnostic procedure supports the following DTC:

DTC P0102 Mass Air Flow (MAF) Sensor Circuit Low Frequency

Conditions for Running the DTC
    • The engine is running.
    • The Engine Speed parameter is more than 544 RPM.
    • This DTC runs continuously in a 12.5 ms loop.

Conditions for Setting the DTC

The ECM detects that the MAF sensor frequency signal is less than 200 Hz for more than 200 ms.

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
    • 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 4-10 g/s at idle to 210 g/s or more at the time of the 1-2 shift.
    • A high resistance of 15 ohms or more on the 12-volt reference circuit may cause this DTC to set. A high resistance will cause a driveability concern before this DTC sets.
    • A high resistance of 10 ohms or more on the ground circuit may cause this DTC to set. A high resistance will cause a driveability concern before this DTC sets.
    • A short between the MAF sensor 12-volt reference circuit and the IAT signal circuit will produce a stalling condition that becomes a Crank/No Start condition.
    • If the condition is intermittent, refer to Inducing Intermittent Fault Conditions in Wiring Systems and Intermittent Conditions .

Test Description

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

  1. This step will determine if a shorted component has caused this DTC to set.

    2.

  2. This step will determine if a shorted component has caused this DTC to set.

    3.

  3. This step will determine if any mechanical faults have caused this DTC to set.

    4.

  4. This voltage drop test will determine if high resistance has caused this DTC to set.

    5.

  5. This step verifies the voltage signal from the ECM to the MAF sensor connector.

    6.

  6. This step will determine if the ECM can accurately process the frequency signal that it receives from the MAF sensor.

    7.

  7. This step will determine if an abnormal resistance of less than 1,150 ohms has skewed the MAF sensor frequency signal.

Step

Action

Values

Yes

No

Schematic Reference: Engine Controls Schematics

Connector End View Reference: Engine Controls Connector End Views or Engine Control Module Connector End Views

1

Did you perform the Diagnostic System Check - Vehicle?

--

Go to Step 2

Go to Diagnostic System Check - Vehicle in Vehicle DTC Information

2

Important: A short to ground on the 12-volt reference circuit of the mass air flow (MAF) sensor that is spliced to other components of the vehicle will result in a no start condition.

Attempt to start the engine.

Does the engine start?

--

Go to Step 3

Go to Step 4

3
  1. Observe the Freeze Frame/Failure records for this DTC.
  2. Turn OFF the ignition for 60 seconds.
  3. Start the engine.
  4. Operate the vehicle within the Conditions for Running the DTC. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records.

Did the DTC fail this ignition?

--

Go to Step 6

Go to Diagnostic Aids

4

  1. Disconnect the MAF/intake air temperature (IAT) sensor.
  2. Attempt to start the engine.

Does the engine start?

--

Go to Step 21

Go to Step 5

5

  1. Turn ON the ignition, with the engine OFF.
  2. Connect a test lamp between the 12-volt reference circuit of the MAF sensor and a good ground. Refer to Probing Electrical Connectors and Circuit Testing in Wiring Systems.
  3. Observe the test lamp.
  4. Disconnect the remaining sensors one at a time that share the 12-volt reference circuit of the MAF/IAT sensor.

Did the test lamp illuminate when any of the sensors were disconnected?

--

Go to Step 19

Go to Step 15

6

  1. Turn OFF the ignition.
  2. Inspect for the following conditions:
    3. • A restricted or collapsed air intake duct
    • A misaligned air intake duct
    • A dirty or deteriorating air filter element
    • Any objects blocking the air inlet screen of the MAF/IAT sensor
    • Any contamination or debris on the sensing elements of the MAF/IAT sensor
    • Any water intrusion in the induction system
    • Any vacuum leak downstream of the MAF/IAT sensor
    • Any type of restriction in the exhaust system--Refer to Restricted Exhaust in Engine Exhaust.
  3. Inspect the harness of the MAF/IAT sensor to verify that it is not routed too close to any of the following components:
    4. • Any aftermarket accessories--Refer to Checking Aftermarket Accessories in Wiring Systems.
    • The ignition coils
    • Any solenoids
    • Any relays
    • Any motors

Did you find and correct the condition?

--

Go to Step 27

Go to Step 7

7

  1. Turn OFF the ignition.
  2. Disconnect the harness connector of the MAF/IAT sensor.
  3. Measure the battery voltage with a DMM.
  4. Turn ON the ignition, with the engine OFF.
  5. Connect a test lamp between the 12-volt reference circuit of the MAF sensor and a good ground. Refer to Probing Electrical Connectors and Circuit Testing in Wiring Systems.
  6. Connect a DMM to the probe of the test lamp and a good ground. Refer to Measuring Voltage Drop and Circuit Testing in Wiring Systems.

Is the voltage within 1.5 volts of the specified value?

B+

Go to Step 8

Go to Step 17

8

Important: All electrical components and accessories must be turned OFF.

  1. Remove the test lamp.
  2. Turn OFF the ignition for 60 seconds to allow the control modules to power down.
  3. Measure the resistance from the low reference circuit of the MAF sensor to a good ground with a DMM. Refer to Probing Electrical Connectors and Circuit Testing in Wiring Systems.

Is the resistance less than the specified value?

5 ohms

Go to Step 9

Go to Step 18

9

  1. Turn ON the ignition, with the engine OFF.
  2. Measure the voltage from the signal circuit of the MAF sensor to a good ground with a DMM. Refer to Probing Electrical Connectors and Circuit Testing in Wiring Systems.

Is the voltage within the specified range?

4-4.4 V

Go to Step 11

Go to Step 10

10

Is the voltage more than the specified value?

4.4 V

Go to Step 14

Go to Step 13

11

  1. Turn OFF the ignition.
  2. Connect the voltage supply and the ground lead of the J 38522 Variable Signal Generator to the vehicle.
  3. Connect the red lead of the J 38522 to the signal circuit of the MAF sensor. Refer to Probing Electrical Connectors in Wiring Systems.
  4. Set the Duty Cycle switch of the J 38522 to Normal.
  5. Set the Frequency switch of the J 38522 to 5 K.
  6. Set the Signal switch of the J 38522 to 5 V.
  7. Start the engine and allow it to idle.
  8. Observe the MAF Sensor parameter with a scan tool.

Is the MAF Sensor parameter within the specified range?

4,950-5,025 Hz.

Go to Step 12

Go to Step 13

12

Important: The J 38522 is able to overcome an abnormal resistance on the signal circuit of up to 1,150 ohms. The MAF sensor will not be able to overcome a resistance this high.

  1. Turn OFF the ignition.
  2. Disconnect the engine control module (ECM).
  3. Test the MAF sensor signal circuit for a high resistance. Refer to Circuit Testing in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 27

Go to Step 20

13
  1. Turn OFF the ignition.
  2. Disconnect the ECM.
  3. Test the MAF sensor signal circuit for the following conditions:
    4. • A high resistance
    • An open circuit
    • A short to ground
    • Refer to Circuit Testing in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 27

Go to Step 22

14

Important: Disconnecting the ECM connectors may eliminate the short to voltage if the signal circuit is shorted to another ECM circuit.

  1. Turn OFF the ignition.
  2. Disconnect the ECM.
  3. Test the MAF sensor signal circuit for the following conditions:
    4. • A short to voltage
    • A short to the IAT signal circuit
    • A short to any 5-volt reference circuit
    • Refer to Circuit Testing in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 27

Go to Step 23

15
  1. Turn OFF the ignition.
  2. Disconnect the ECM.
  3. Test the 12-volt reference circuit of the MAF sensor for the following conditions:
    4. • A short to ground
    • A short to the IAT low reference circuit
    • A short to the IAT signal circuit.
    • Refer to Testing for Short to Ground and Circuit Testing in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 27

Go to Step 16

16

Test the 12-volt reference circuit of the following components for a short to ground:

    • The crankshaft position (CKP) sensor
    • The camshaft position (CMP) sensor bank 1 intake
    • The CMP sensor bank 1 exhaust
    • The CMP sensor bank 2 intake
    • The CMP sensor bank 2 exhaust
         Refer to Testing for Short to Ground and Circuit Testing in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 27

Go to Step 23

17

Test the MAF sensor 12-volt reference circuit for the following conditions:

    • A high resistance
    • An open circuit

Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 27

Go to Step 22

18

Test the MAF sensor low reference circuit for the following conditions:

    • A high resistance
    • An open circuit

Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 27

Go to Step 22

19

Test for shorted terminals and poor connections at the affected component. Refer to Testing for Intermittent Conditions and Poor Connections , Repairing Connector Terminals , and Connector Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 27

Go to Step 24

20

Test for an intermittent and for a poor connection at the MAF/IAT sensor. Refer to Testing for Intermittent Conditions and Poor Connections , Repairing Connector Terminals , and Connector Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 27

Go to Step 25

21

Test for shorted terminals and poor connections at the MAF/IAT sensor. Refer to Testing for Intermittent Conditions and Poor Connections , Repairing Connector Terminals , and Connector Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 27

Go to Step 25

22

Test for an intermittent and for a poor connection at the ECM. Refer to Testing for Intermittent Conditions and Poor Connections , Repairing Connector Terminals , and Connector Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 27

Go to Step 26

23

Test for shorted terminals and poor connections at the ECM. Refer to Testing for Intermittent Conditions and Poor Connections , Repairing Connector Terminals , and Connector Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 27

Go to Step 26

24
  1. Replace the shorted component.
  2. Refer to the following appropriate removal and replacement procedure for that sensor:

Did you complete the replacement?

--

Go to Step 27

--

25

Replace the MAF/IAT sensor. Refer to Mass Airflow Sensor Replacement .

Did you complete the replacement?

--

Go to Step 27

--

26

Replace the ECM. Refer to Control Module References in Computer/Integrating Systems for replacement, setup, and programming.

Did you complete the replacement?

--

Go to Step 27

--

27
  1. Clear the DTCs with a scan tool.
  2. Turn OFF the ignition for 60 seconds.
  3. Start the engine.
  4. Operate the vehicle within the Conditions for Running the DTC. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records.

Did the DTC fail this ignition?

--

Go to Step 2

Go to Step 28

28

Observe the Capture Info with a scan tool.

Are there any DTCs that have not been diagnosed?

--

Go to Diagnostic Trouble Code (DTC) List - Vehicle in Vehicle DTC Information

System OK