P0491 Fault Code
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Have a 2003 996 tt. The 0491 cel code has come up twice in the last two months. The first time I reset and cleared the cel . About 6weeks later(today), it came up again. The code says it's the secondary air system. Do I need to worry about this code or is this a 'have a look at the next service' item? Thanks for the help.
Mike
Mike
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P0491 Secondary Air Injection System, Bank 1 - Below Limit
Possibly cause(s):
- Electrical fault in power supply or line between relay and secondary air injection pump
- Secondary air injection pump relay mechanically faulty
- Mechanical fault in electrical secondary air valve
- Pneumatic secondary air valve faulty/sluggish
- Electrical fault in secondary air injection pump
- Mechanical fault in secondary air injection pump or secondary air injection pump blocked
- Vacuum system leaking
- Air hose to secondary air injection pump slipped off or constricted
Possibly cause(s):
- Electrical fault in power supply or line between relay and secondary air injection pump
- Secondary air injection pump relay mechanically faulty
- Mechanical fault in electrical secondary air valve
- Pneumatic secondary air valve faulty/sluggish
- Electrical fault in secondary air injection pump
- Mechanical fault in secondary air injection pump or secondary air injection pump blocked
- Vacuum system leaking
- Air hose to secondary air injection pump slipped off or constricted
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I am getting the 0491 and 0492 codes.
Shop tells me it needs a new pump, and will have to have the engine lowered to replace it. Over $3K total. I'd like a second opinion. Is it reachable to check for loose plug or hose(s) w/o lowering the motor?
Shop tells me it needs a new pump, and will have to have the engine lowered to replace it. Over $3K total. I'd like a second opinion. Is it reachable to check for loose plug or hose(s) w/o lowering the motor?
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Thx Loren - that definitely helps. But are these readily accessable from under the hood? From under the car? That was the bulk of my query...
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I'm going to check everything in there. I've got new billet DV valves, so I'll find that DIY you wrote up and change them out as well.
Hard to believe my pump failed at 19xxx miles...
Thx.
Hard to believe my pump failed at 19xxx miles...
Thx.
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I haven't gotten into it yet.
In order to check all the lines, I'll have to remove a few things in the engine compartment. Want to give myself plenty of time, as I haven't messed around back there on this car much.
I did find the Sec Air Pump, ascertain that it does in fact work as advertised. Starts on start up, and shuts off after a minute or so. I'm fairly confident that it's a leak somewhere.
I do have new Div valves to install from UMW, so those will go in as well.
We'll see. I'll post my results.
In order to check all the lines, I'll have to remove a few things in the engine compartment. Want to give myself plenty of time, as I haven't messed around back there on this car much.
I did find the Sec Air Pump, ascertain that it does in fact work as advertised. Starts on start up, and shuts off after a minute or so. I'm fairly confident that it's a leak somewhere.
I do have new Div valves to install from UMW, so those will go in as well.
We'll see. I'll post my results.
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It's #6 in Loren's diagram.
Doesn't look like the drawing though. It's right below the oil fill cap. You'll hear it (and can feel it running) on start up...
I swapped my Div valves this weekend, and cleared the codes. No codes yet after 4 - 5 starts with 3-4 hoours driving. Keeping my fingers crossed for now...
Edit: Think I've pretty much confirmed I had a bad DV. Blowing into the "big hole" of one of them leaks air out the small (vac) hole... $3K saved and now I know who NOT to go to for service...
Thx R-list!
Doesn't look like the drawing though. It's right below the oil fill cap. You'll hear it (and can feel it running) on start up...
I swapped my Div valves this weekend, and cleared the codes. No codes yet after 4 - 5 starts with 3-4 hoours driving. Keeping my fingers crossed for now...
Edit: Think I've pretty much confirmed I had a bad DV. Blowing into the "big hole" of one of them leaks air out the small (vac) hole... $3K saved and now I know who NOT to go to for service...
Thx R-list!
Last edited by MitchB; 06-02-2008 at 04:45 PM.
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I can remove the pump in less than 45 minutes.. You do NOT need to drop the engine...
However, is telling you that is bending you over!!! Again the pump can be removed thru the engine compartment opening..
Glad you installed the valves..
I strongly recommend installing small tie wraps to all the small hose connections.
However, is telling you that is bending you over!!! Again the pump can be removed thru the engine compartment opening..
Glad you installed the valves..
I strongly recommend installing small tie wraps to all the small hose connections.