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YOUR RESEARCH996 Fault codes
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Check mass air flow sensor
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P0030 and P0028 996 Carrera 4 , checked AOS via vacuum at oil filler cap nothing drastic vacuum wise, threw a wobbly the other day with erratic idle and thereafter fine.
Popped through to my mates house tonight, car running fine but eml light came on ?
Thoughts learned gents?
P0030 is for the bank 1 O2 sensor heating circuit, P0028 indicates a fault with the bank 2 Variocam Solenoid Valve circuit. I would zero in on the P0028 fault first to see what's going on.
I’d treat those as two separate clues rather than assuming it’s AOS.
P0030
is usually the oxygen sensor heater circuit, so I’d be looking at the pre-cat lambda sensor wiring/plug/fuse side first, especially if the car otherwise runs normally.
P0028
points more towards the cam/Variocam control side on one bank, so that could explain the rough/erratic idle episode if it briefly got unhappy.
If it has only done it once and is now running fine, I’d clear the codes and see which one comes back first. Check the obvious bits first: lambda sensor plugs/wiring, cam solenoid wiring/connectors, oil level and oil condition. AOS is always worth ruling out on these, but from those codes alone it wouldn’t be my first suspect.
Your chasing a vacuum leak, get a smoke test done, don’t rule out AOS, I had no typical failure signs of AOS but that was part of my problem. I presume youve checked the MAF?
Good luck
Those point to a common air leak on both sides rather than chasing one bank.
A vacuum/air leak is the obvious starting point: intake boots, throttle body area, oil filler tube/cap, AOS pipework, vacuum lines and any split or loose hose after the MAF. I’d also give the MAF a look, as a bad or dirty MAF can make both banks unhappy and throw mixture codes.
The earlier AOS check is useful, but it doesn’t rule out the rest of the intake/vacuum system.
