This bulletin applies to 2008-2013 Volkswagen Passat sedans, with regard to crankcase breather diagnosis. The technician may find rough running, engine noise and MIL on with DTCs P0300, P0301, P0302, P0303, P0304, P2279, P1297, P1093 or P2187 stored in the ECM.
P0300.........................random/multiple cylinder misfire detected
P0302........................ cylinder 1 misfire detected
P0302........................ cylinder 2 misfire detected
P0303........................ cylinder 3 misfire detected
P0304........................ cylinder 4 misfire detected
P2279......................... intake air system leak
P1297......................... charger throttle connection, drop in pressure
P1093......................... bank 1 fuel measuring system 2 malfunction
P2187......................... system too lean at idle, bank 1
A faulty PCV valve will allow pressurized intake air back into the valve cover/crankcase. This pressurized air can blow out of several openings. The oil fill cap, air filter and dipstick should first be checked for evidence of oil blow out.
With the engine off, remove the engine cover and locate the hose connecting the intake manifold to the crankcase. Disconnect the hose from the intake manifold side and clean off any residue with a cloth. Blow into the hose. If there is some air resistance, the check valve is operating correctly. If there is no resistance, the PCV valve should be replaced.
With the engine running, disconnect the hose from the valve cover. Plug the hose and check idle quality. If idle quality improves, replace the PCV valve. With the engine running, remove the dipstick. If idle quality improves, replace the PCV valve. Remove the oil fill cap. Place a stiff piece of paper over the opening. The paper should be sucked against the hole within a few seconds if the PCV valve is operating correctly.
The best way to ensure the functionality of the system is to look at fuel trim readings in MVB32. If faults pertaining to the PCV valve are found, do not erase the faults. Proceed with the following steps prior to following the GFF test plan to avoid erasing fuel trim readings.
1. Using VAS tester, read current fuel trim level in MVB 32 field 1 (idle fuel trim) and 2 ((part throttle). Normal values are 0 +/- 3 in both fields.
2. Replace the original valve with a known-good test part.
3. Make sure no additional loads such as A/C and heated seats are turned on during the test.
4. If the noise goes away or the engine is no longer running rough, PCV valve replacement is recommended.
5. Using VAS tester, run basic settings 32 for at least 5 minutes.
6. While running basic settings 32 for 5 minutes, we can monitor fields 1 and 2 for fuel trim readings.
7. If fuel trim values improve and move closer to 0, valve replacement is recommended. If values do not improve, re-install the original valve. Use of the GFF is permitted at this point.
