tx170754

Hi everybody,
I've had two CEL P0491 codes recently, checked the archives and found some answers. The small hose on the left bank looks OK, is there anyhthing else I should look ? Somebody mentioned a Service Buletin for a redesigned hose, what hose would that be, please. I'm wondering if there is somebody there who was able to fix this problem or should I expect to live with it and erase the code each time it shows up.
Any help would be very appreciated,
Thanks,
Dan

ttuling

The redesigned hose was an assembly of three thin vacuum hoses with molded fittings at the ends which connect the solenoid valve on top of the engine to the two valves at the back of the engine which let air into the exhaust.

If you saw the picture on the forum of a disconnected vacuum hose related to the code, that's only half the story -- you should check the hose that's still connected to the solenoid valve in the photo, following it to its two destinations behind the engine.

Yet if that cracks I'd expect you'd also have a P0492 code which you didn't mention.

Tom

tx170754

Tom,
First I would like to thank you for your answer.
I've only had the P0491 two times, not the P0492, would this be related to the fuse (as Paul mentioned)or also to the disconected hose in the picture ?
Thanks again,
Dan

ttuling

I suspect Paul's talking about a fuse for the secondary air blower which feeds air to both banks' exhaust through the valves on the back of the engine after cold starts. If it doesn't work, you'd get trouble codes for both banks.

If the hose in picture is disconnected, then neither valve on the back of the engine opens to let air into the exhaust, and you'd get trouble codes for both banks.

The other hose in the picture, the one still connected to the solenoid valve, splits into two hoses, one for each valve on the back of the engine. You can follow them back. It seems unlikely, but if one of those is just barely cracked or kinked, maybe it would cause an infrequent trouble code. Not likely, but easy to check.

If that's all okay, I don't think there's a frequent cause to point at, but I wonder if the valve for that bank mechanically sticky, or as others have suggested maybe an oxygen sensor for that bank is slow to respond when cold which the ECM reads as insufficient secondary air. But you don't mention any oxygen sensor trouble codes, so that also seems unlikely.

Tom

tx170754

Tom,
Thanks again for the info. The car is a 2001 with only 36,000 miles.It came out of a lease in Florida,(I got it with 29,000 miles) so no winters, it looks very clean. I will look at all those hoses and at the fuse (any idea where that could be, checked both front panel and rear right but didn't see it) If nothing obvious shows up then I would probably wait until the code stays always on and go from there.
Any other advice ?
Thanks,
Dan

roughyear

should be under their warranty.. take it back to the $tealer.