Customer Concern: Runs horribly, misfires, responds poorly to throttle, low power. MIL on, multiple DTC's. P0124/16518 Oxygen Sensor (o2) no activity detected Bank 1 Sensor 1, misfire DTC's P0300/16684, P0301/16685, P0302/16686, P0303/16687, P0304/16688, P0102/16486 - Mass Airflow sensor (MAF) circuit low input, P0112/16496 - Intake air temperature sensor circuit low input.
Tests/Procedures: 1. Check and verify that there are no vacuum leaks or unmetered air leaks.
2. Check and verify that the air filter, all inlet screens and throttle body are clear and clean (Never use an aerosol cleaner to clean a throttle body, damage to the throttle body electronics may result. Use a rag dampened with cleaner to wipe the throttle clean).
3. Check and verify that the fuel pressure is 36 PSI at idle, with vacuum to the Fuel Pressure (FP) regulator.
No trace of fuel in the vacuum hose should be indicated.
4. Check the Mass Airflow Sensor (MAF) grams/second (G/S) readings as follows: at 830-870 rpm idle, 3.5 G/S or more (4 to 4.5 G/S preferred), at 2500 rpm no load, 9 to 15 G/S (11 to 12 G/S preferred).
5. Wide Open Throttle (WOT) road load (Drive the vehicle at 45 MPH in 3rd gear and perform a WOT acceleration, observe maximum indicated MAF G/S readings) 90 or more G/S should be present (prefer above 100 G/S).
6. A MAF that exhibits consistently lower than normal G/S readings can cause a P1128 code to set. A MAF with internal circuit faults or poor connection can cause the P0102 and P0112.
7. Using a fully functional VW compatible scan tool, test the Oxygen Sensor (O2) as follows: enter 'Engine' (address word 01), select 'Basic settings' (option 04) and enter display group 034.
8. Run the vehicle at 2,200-2,500 RPM, until catalyst temperature in display field 3 reads 365 degrees C or more. Continue to hold the speed until the 4th field switches from 'test off' to 'test on'. Continue to hold the speed and watch for field 4 to turn to B1S1 OK. If it does not, the O2 sensor is faulty.
Tech Tips: Replacement of the B1S1 O2 sensor cured most of the ills of this poorly maintained car, but it still needed a complete tune-up and the MAF tested borderline...customer refused repairs.