Error codes P0507 and P0102 after replacing MAF sensor

SOURCE: after changing fuel pump 2 days ago on my 97

You can test the MAF before replacing. It may be a problem with the circuit itself or just a fluke from another problem that is connected to this sensor.

There are two basic types of mass airflow sensors: hot wire and hot film. In the first type, a very thin wire (about 0.2 mm thick) is used as the heated element.
Components of a hot wire-type mass airflow sensor. Courtesy of Ford Motor Company. The element temperature is set at 100° to 200°C above incoming air temperature. Each time the ignition switch is turned to the off position, the wire is heated to approximately 1,000°C for 1 second to burn off any accumulated dust and contaminants.
The second type uses a nickel foil sensor, which is kept 75°C above ambient air temperatures. It does not require a burn-off period and therefore is potentially longer lasting than the hot wire type.
A faulty MAF will cause driveability problems resulting from incorrect ignition timing and improper air/fuel ratios.
Vane-type MAF Sensors
A vane-type MAF sensor is found on many import and domestic vehicles with EFI. All intake air must flow through the sensor. Some MAF sensors are called volume air flow meters

• Begin checking a vane-type MAF sensor by checking the voltage supply wire and the ground wire to the MAF module before checking the sensor voltage signal.
• Always follow the recommended test procedure in the manufacturer's service manual and use the specifications supplied by the manufacturer.
• Typically, to test the sensor, a digital multimeter (DMM) is used and set on a DC voltage scale. The negative meter lead is connected to ground and the red lead to the MAF signal wire.

• Turn on the ignition switch and press the min/max button, if available, on the DMM.
• Slowly push the MAF vane from the closed to the wide-open position, and allow the vane to slowly return to the closed position.

• Observe the maximum and minimum voltage readings as the vane was moved.
• If the minimum voltage signal is zero, there may be an open circuit in the MAF sensor variable resistor.
• When the voltage signal is not within the manufacturer's specifications, replace the sensor.

• Some vehicle manufacturers specify ohmmeter tests for the MAF sensor.
• With the MAF sensor removed, connect the ohmmeter across the sensor's output and input terminals.

• The resistance at these terminals is normally 200 to 600 ohms.
• Connect the ohmmeter leads to the specified MAF sensor terminals, and move the vane from the fully closed to the fully open position.
• With each specified meter connection and vane position, the ohmmeter should indicate the specified resistance.

• When the ohmmeter leads are connected to the sensor's input and output terminals, the ohmmeter reading should increase smoothly as the sensor vane is opened and closed.
• To check a vane-type MAF with a lab scope, connect the positive lead to the output signal terminal and the negative scope lead to a good ground.
• This type MAF should display an analog voltage signal when the engine is accelerated. A defective MAF will have sudden and erratic voltage changes.

• To check the MAF sensor's voltage signal and frequency, connect a voltmeter across the MAF voltage signal wire and ground wire.
• Start the engine and observe the voltmeter reading.
• On some MAF sensors, this reading should be 2.5 volts.
• Lightly tap the MAF sensor housing with a screwdriver handle and watch the voltmeter pointer.
• If the pointer fluctuates or the engine misfires, replace the MAF sensor.
• Some MAF sensors have experienced loose internal connections, which cause erratic voltage signals and engine misfiring and surging.
• Set the DMM so that it can read the frequency of DC voltage.
• With it still connected to the signal wire and ground, the meter should read about 30 Hz with the engine idling.
• Now, increase the engine speed, and record the meter reading at various speeds.
• Graph the frequency readings. The MAF sensor frequency should increase smoothly and gradually in relation to engine speed.
• If the MAF sensor frequency reading is erratic, replace the sensor.

• When a scanner is used to diagnose a General Motors' vehicle, one test mode displays grams per second from the MAF sensor. This mode provides an accurate test of the MAF sensor.
• The grams per second reading should be 4 to 7 with the engine idling.
• This reading should gradually increase as the engine speed increases.
• When the engine speed is constant, the grams-per-second reading should remain constant.
• If the grams-per-second reading is erratic at a constant engine speed or if this reading varies when the sensor is tapped lightly, the sensor is defective.
• A MAF sensor fault code may not be present with an erratic grams-per-second reading, but the erratic reading indicates a defective sensor.
• Frequency-varying types of MAF sensors can be tested with a lab scope.
• The waveform should appear as a series of square waves.

• When the engine speed and intake air flow increases, the frequency of the MAF sensor signals should increase smoothly and proportionately to the change in engine speed.
• If the MAF or connecting wires is defective, the trace will show an erratic change in frequency.

Stephen

• 21873 Answers
• Posted on Aug 25, 2012

SOURCE: Why is my Grand Prix surging/stalling when ideling?

If you did not disconnect the battery and drain the voltage from the ECM, it could be using old settings when the problem existed.
When a problem occurs, the computer tries to correct it or find new settings to work around the problem. When you fix a problem you have to clear the codes and sometimes erase the memory from the computer to allow it to start back at the factory settings.
When you disconnect something and the check engine light comes on, the computer goes into limp mode and uses values for the sensors preset by the factory. The car will almost always run rich to ensure the driver can get back to a place for repairs.