P0491/ 0492 - Can I still drive my GTS without damaging it?

MC47 · Aug 27, 2024

It's a Liberty Walk kit, manufactured in Japan.

Catmanv2 · Aug 28, 2024

That seems like the secondary air, so yes. But you probably want to get a scanner that has the right definitions

C

BobDPipe · Aug 28, 2024

Hi All,
So I am following this with interest as I have the PO492 code only.
In my little brain, I am reasoning that as it is only PO492, the likelihood is that the pump (which runs fine), main pipework, tank etc. must all be fine and good as RH bank is all good and not throwing the PO491 code.
Therefore it must be the hose connecting to the left hand valve or the valve itself. I just disconnected the pipe off the metal pipe and used my special vacuum tester to hold a vacuum for 30 seconds (after that point my tongue hurt). So pipe seems fine and the diaphragm inside the valve must be fine too. So I am of the mind that it is the valve, although I can hear it actuating.
I guess next best thing is to remove valve and see if I can see it actuating and then somehow apply vacuum tester whilst testing that valve is actually open.
I am thinking that if the valve is a bit sticky, it may be sounding good, but not allowing sufficient flow.

As said above, if I had both codes, then that would point to larger leak, fan, solenoid or tank issue. Interestingly new vacuum tank is £20 with VAT so $30 or so. Secondhand Fan is £190 with VAT ($280) and new solenoid is £35 ($48). The valves are quite expensive at £125 secondhand, so hoping I can resurrect mine.

baba · Aug 28, 2024

AGR valve should be Pierburg # 7.22296.02.0 New much cheaper.

MaseratiByChance · Aug 28, 2024

BobDPipe said:
Hi All,
So I am following this with interest as I have the PO492 code only.
In my little brain, I am reasoning that as it is only PO492, the likelihood is that the pump (which runs fine), main pipework, tank etc. must all be fine and good as RH bank is all good and not throwing the PO491 code.
Therefore it must be the hose connecting to the left hand valve or the valve itself. I just disconnected the pipe off the metal pipe and used my special vacuum tester to hold a vacuum for 30 seconds (after that point my tongue hurt). So pipe seems fine and the diaphragm inside the valve must be fine too. So I am of the mind that it is the valve, although I can hear it actuating.
I guess next best thing is to remove valve and see if I can see it actuating and then somehow apply vacuum tester whilst testing that valve is actually open.
I am thinking that if the valve is a bit sticky, it may be sounding good, but not allowing sufficient flow.

As said above, if I had both codes, then that would point to larger leak, fan, solenoid or tank issue. Interestingly new vacuum tank is £20 with VAT so $30 or so. Secondhand Fan is £190 with VAT ($280) and new solenoid is £35 ($48). The valves are quite expensive at £125 secondhand, so hoping I can resurrect mine.

I would agree with all you said. I would perform a couple more vacuum test before replacing parts. First, I would disconnect the main source vacuum hose near the throttle body and put a vacuum gauge on the source side. Would expect about 16 to 18 inches vacuum at idle. Next, I would reconnect source hose and connect it to air valves vacuum hose while pinching off the other sides vacuum hose. This must be done on a cold engine and within the first 30 to 60 seconds. The vacuum at the air valve should be what source vacuum is. It's possible that the vacuum is low only allowing enough flow to open one valve. If that's the case, then isolating the leak is next step.

BobDPipe · Aug 30, 2024

Thanks for the answers. I have found the valve much cheaper using that ref, however I am waiting on ordering as after messing about with the valve and getting it to click by applying a strong vacuum, the check engine is now staying off and the live data on start up looks balanced, so maybe I will get away with it. Perhaps it was just a bit sticky.

P0491/ 0492 - Can I still drive my GTS without damaging it?

MC47

Catmanv2

BobDPipe

baba

MaseratiByChance

BobDPipe

Top Contributors this Month

Recommended Communities