P0102

MASS AIR FLOW SENSOR





Fault Symptoms.
CHECK ENGINE lamp (MIL) on. Engine reluctant to start, poor driveability and high fuel consumption.

Conditions.
P0102
Engine speed above 400 rpm and intake air mass less than 0.3 V / 1.11 g/s.

P0103
Engine speed 1000 rpm and intake air mass greater than 3.2 V / 84.5 g/s.

Diagnostic Help.
The performance of the mass air flow sensor can be ascertained with an ISAT scan tool.
- Switch OFF all electrical equipment. On cars with automatic transmission, also move the selector lever to N or P.
- Connect the ISAT scan tool and start the engine.
- Select "READ FUNCTIONS".
- Select "MASS AIR FLOW SENSOR".

Check that the ISAT scan tool shows the following air mass as a function of engine rpm:
^ idling speed about 0.8 V
^ at 2500 rpm (no load) about 1.2 V

Slightly higher values will be obtained with a cold engine.

Check The Wiring.
Intermittent faults may occur as a result of temporary short circuits and breaks in the wiring. Jiggle the wiring at several points and in different directions to ascertain whether the wiring harness, including any connectors, is causing the trouble. Observe the multimeter, ISAT scan tool or test lamp while doing this.





Diagnostic Procedure.
1. Check the mass air flow sensor's ground connection and power supply
- Unplug the mass air flow sensor's 4-pin connector.
- Turn the ignition switch to the ON position.
- Connect the test lamp to:
^ Battery positive (B+) and pin 1.
^ Battery positive (B+) and pin 2.
^ pin 3 and battery negative (B-).

The test lamp should light up in all three cases.

Did the test lamp light up?
YES: Continue with point 2.
NO: Repair or replace the lead in question and proceed to point 3.





2. Check the control module's mass air flow sensor input

- Connect an ordinary 1.5 V battery (in good condition) as follows:
^ positive pole to pin 4
^ negative pole to pin 2
- Connect the ISAT Scan Tool.
- Turn the ignition switch to the ON position.
- Select "READ FUNCTIONS".
- Select "MASS AIR FLOW SENSOR".

The ISAT scan tool should show a reading of about 1.5 V.

Are all readings OK?
YES: Change the mass air flow sensor and continue with point 3.
NO: Check the lead in question and repair or replace it if necessary. Then continue with point 3.





3. Final check

- Clear the diagnostic trouble code.
- Implementation of driving cycle:
^ Drive the car at varying engine loads and rpm for 5 minutes.
- Evaluation of driving cycle:
^ Check whether the diagnostic trouble code has recurred.

Has the diagnostic trouble code recurred?
YES: Continue at "Before Replacing a Control Module". Component Tests and General Diagnostics
NO: The steps taken to rectify the fault were correct.