In VW/Audi 01M, 01N and 01P units, regulated line leaks to exhaust at the pressure regulator, it creates a low pressure condition. Wear at the inner balance spools prevent the valves from stroking, which can cause high line pressure. Wear at the inboard bore also affects the K1 clutch circuit, which can result in 1-2 or 2-3 shift complaints. Sonnax oversized main pressure regulator valve 119940-03K allows the valve bores to be refurbished.
Vacuum testing at the port(s) indicated fails to hold the recommended minimum in-Hg, or if wear is visually detected.