115 Mass Air Flow Sensor - Above Limit

P0103

115 Mass Air Flow Sensor - Above Limit

Function
The mass air flow sensor is installed between the air cleaner and the throttle valve, and measures the mass air flow taken in by the engine. An electrically heated platinum resistance film is cooled by the air flow. A control circuit corrects the heating current in such a way that the temperature of the resistance film rises constantly in relation to the intake air temperature. The heating current is then a means of measuring the mass air flow. With this method of measurement, the air density is also taken into consideration, as it helps to determine the amount of heat emitted from the heated body into the air. A temperature sensor is integrated for measuring the intake air temperature.

Diagnosis conditions
- Engine running
- Battery voltage > 8 V

P0102 - P0103:

A - DME relay

Diagnosis Procedure










1 Check wiring from MAF sensor to DME control module for continuity.
1. Remove connector of MAF sensor.
2. Connect special tool 9637 to wiring harness (DME control module connector).
3. Connect ohmmeter to special tool 9637, pin III/23, and MAF sensor connector, pin 5.

Display: 0 - 5 ohms

If infinity ohms is displayed, check wiring harness for chafing and pinching damage.

2 Check wiring from MAF sensor to DME control module for short to ground.
1. Remove connector of MAF sensor.
2. Connect special tool 9637 to wiring harness (DME control module connector).
3. Connect ohmmeter to special tool 9637, pin III/23, and ground.

Display: infinity ohms

If 0 - 5 ohms is displayed, check wiring harness for chafing and pinching damage.

3 Check signal from MAF sensor.
1. Check voltage signal from MAF sensor with "Ignition on" (with Porsche System Tester 2 in the Actual values/mass air flow menu, or with a voltmeter and special tool 9637).

Nominal value: 0.9 to 1.1 V

2. Start the engine.

Nominal value: 1.2 to 1.5 Volts at idle speed

4 Clean air filter and replace filter element.
1. Clean pure air side of air filter (extract dirt, do not blow out with compressed air with mass air flow sensor installed).
2. Replace filter element.

5 Check wiring from MAF sensor to DME control module for short to B+.
1. Remove connector of MAF sensor.
2. Connect special tool 9637 to wiring harness (DME control module connector).
3. Connect voltmeter to special tool 9637, pin III/23 (positive), and ground.
4. Switch on the ignition.
5. Display: 0 V

If battery voltage is displayed, check wiring harness for chafing and pinching damage.

6 Check and clean throttle jacking unit.
Read out throttle actual value at idling speed (engine at operating temperature, air conditioning switched off).
Nominal value: less than 4 %

If throttle actual value is greater than 4 %, clean throttle jacking unit (oil residue around the throttle).