Volkswagen Golf: 1.4 TSI ACT cylinder deactivation solenoid fault

The Golf Mk7 with 1.4 TSI ACT (Active Cylinder Technology, engine codes CZCA/CZC) uses electromagnetic solenoid valves in the valve train to deactivate cylinders 2 and 3 at light load. Carbon buildup from the PCV system and heat cycling cause the solenoids to stick or fail electrically. A failed solenoid leaves the affected cylinder unable to open its valves correctly, producing a persistent misfire (P0300 random, P0302 cylinder 2 specific). In severe cases the cam follower on the deactivated cylinder suffers accelerated wear, escalating repair costs significantly.

• Engine Management Light with fault codes P0300 or P0302
• Rough idle with misfire vibration felt through the chassis
• Hesitation and stumble under light throttle input
• Fuel economy worse than the published specification
• ACT no longer entering two-cylinder mode — engine stays on four cylinders permanently

1. 1

   Test solenoid resistance across both ACT solenoids and compare against VW specification.

2. 2

   Check cam follower condition on the deactivated cylinders via the cam cover inspection port.

3. 3

   Review whether a PCV system service or engine decarbonise has been performed.

4. 4

   If a workshop inspection is possible: Perform an OBD-II scan specifically checking for P0300 (random misfire) and P0302 (cylinder 2 misfire).

5. 5

   If accessible, borescope cylinders 2 and 3 for carbon buildup.

Parts involved: PCV / oil separator.

$550 to $1,800 at New Zealand independent workshop rates. That is for this job on its own, not for the car.

An estimate, in NZD, for the repair as normally carried out. What a specific car costs depends on which part has failed and what it damaged on the way — treat this as the floor for a negotiation, not a quote.

• “Has the engine ever produced a cylinder-specific misfire fault code such as P0302?”
• “Have the ACT solenoid valves been inspected or replaced?”
• “Is the ACT cylinder deactivation feature still functioning — does the gauge show 2-cylinder mode at cruise?”
• “Has the engine been decarbonised or had a PCV breather system service?”

The failure described above is documented in published sources — owner forums, technical service bulletins, recall notices and workshop write-ups — held in our fault database. The inspection instructions and the cost estimate are KickTyres’ own interpretation of them, and it is a starting point for an inspection rather than a manufacturer statement.