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For 1990-2009 cars only
Makes 🢒 Geo 🢒 1996 🢒 Tracker - 4WD 🢒 Engine 🢒 Engine Controls - 1.6L 🢒 DTC P0102 Mass Air Flow (MAF) Sensor Circuit Low Frequency

Schematic Reference: Engine Controls Schematics

Circuit Description

The mass air flow (MAF) sensor measures the amount of air which passes through it in a given amount of time. The engine control module (ECM) uses this information to determine the operating requirements of the engine in order to control fuel delivery. The ECM 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 ECM from the MAF sensor also increases. When the air flow decreases, the current seen by the ECM also decreases. The MAF sensor is located between the air intake tube and the air cleaner in the LH front area of the engine compartment.

Conditions for Running the DTC

The engine is running.

Conditions for Setting the DTC
    • MAF sensor output current is less than 0.64 mA.
    • Condition is present for longer than 5 seconds.

Action Taken When the DTC Sets
    • The ECM illuminates the malfunction indicator lamp (MIL).
    • The ECM records the operating conditions at the time the diagnostic fails. This information is stored in the Freeze Frame buffer.
    • The ECM enters the Fail-Safe Function and determines injector drive time according to TP sensor and engine speed.

Conditions for Clearing the MIL/DTC
    • The MIL turns OFF after three consecutively passing trips without a fault present.
    • A History DTC clears after 40 consecutive warm-up cycles without a fault.
    • Use the scan tool Clear DTC Information function or disconnect the ECM battery feed 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 it 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 connectors and 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. A wide open throttle (WOT) 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 at least 100 g/s during the 1-2 shift. Check for a plugged intake air a duct or dirty air filter element.

An intermittent malfunction may be caused by a fault in the MAF sensor circuit. Inspect the wiring harness and components for any of the following conditions:

    • Backed out terminals.
    • Improper mating of terminals.
    • Broken electrical connector locks.
    • Improperly formed or damaged terminals.
    • Faulty terminal to wire connections.
    • Physical damage to the wiring harness.
    • A broken wire inside the insulation.
    • Corrosion of electrical connections, splices, or terminals.

If the DTC P0102 cannot be duplicated, the information included in the Freeze Frame data can be useful in determining 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 Powertrain OBD System Check 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.

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

    3.

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

    4.

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

Step

Action

Value(s)

Yes

No

1

Did you perform the Powertrain On-Board Diagnostic (OBD) System Check?

--

Go to Step 2

Go to Powertrain On Board Diagnostic (OBD) System Check

2

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

Is the MAF sensor display at the specified value?

0 g/s

Go to Step 4

Go to Step 3

3

  1. Turn ON the ignition, leaving the engine OFF.
  2. Use the scan tool clear information function.
  3. Operate the vehicle within the Freeze Frame conditions as noted.

Is the MAF sensor display at the specified value?

0 g/s

Go to Step 4

Go to Diagnostic Aids

4
  1. Check for any of the following conditions:
    2. • Objects blocking the MAF sensor inlet screen.
    • Intake manifold vacuum leaks.
    • Throttle body vacuum leaks.
    • EGR valve vacuum leaks.
    • A faulty, missing, or incorrectly installed PCV valve.
  2. Repair as necessary.

Was a repair necessary?

--

Go to Step 11

Go to Step 5

5
  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 DMM connected to ground.

Is the voltage near the specified value?

B+

Go to Step 6

Go to Step 7

6
  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 ECM using a DMM.
  5. Measure the voltage.

Is the voltage within the specified value?

1.0 to 1.6 volts

Go to Step 10

Go to Step 8

7

Locate the open or the short circuit in the MAF sensor ignition feed circuit. Repair as necessary. Refer to Wiring Repairs in Wiring Systems.

Is the action complete?

--

Go to Step 11

--

8

  1. Check the MAF sensor signal circuit for the following conditions:
    2. • An open between the ECM and the MAF sensor.
    • A short between the ECM and the MAF sensor.
    • A poor connection at the MAF sensor.
  2. Repair as necessary. Refer to Wiring Repairs in Wiring Systems.

Was a repair necessary?

--

Go to Step 11

Go to Step 9

9

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

Is the action complete?

--

Go to Step 11

--

10

Replace the ECM. Refer to Engine Control Module Replacement.

Is the action complete?

--

Go to Step 11

--

11
  1. Perform the scan tool Clear DTC Information function and road test vehicle within Freeze Frame conditions that set the DTC.
  2. Review the scan tool data and check for DTCs. The repair is complete if no DTCs are stored.

Are any DTCs displayed on the scan tool?

--

Go to the Applicable DTC Table

System OK