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P0299 Turbo underboost CEL

14281 Views 5 Replies 2 Participants Last post by  Passatfan2
Today was hot and humid, son tells me the CEL came on while driving, symptoms were lower power than normal. Scanned it and got the P0299 for underboost condition. The inlet air pipe is solid, no other signs of air pipes loose.

Backstory: Got the 2004 GLS 1.8T emission tested last Thursday, it passed :thumbup: This was after I replaced the SAIP, previously all my CEL's were related to inadequate flow in SAI system.

Weird ? or am I missing something? or if the old Combi valve was not seating fully closed, would I be leaking boost back through the SAIP ?

Last week when I did the SAIP, I found water in the outlet pipe of original SAIP, so my combi valve is suspect. Don't know if this new code P0299 is related or just another layer of VW joy:confused:
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Had the same code 2 weeks ago and follow the ross-tech wiki recommendations.

16683/P0299/000665 - Boost Pressure Regulation: Control Range Not Reached

Possible Symptoms

Reduced Power Output
Limp Mode

Possible Causes

Hoses/Pipes incorrect connected, disconnected or leaking
Charger Pressure Control defective
Turbocharger faulty
Diverter Valve faulty

Possible Solutions

Check Hoses/Pipes to/between Components
Check / Clean / Replace Charge Pressure Control
Check Turbocharger
Check Diverter Valve

Special Notes

If the Turbocharger is faulty due to mechanical / internal problems or the exhaust system is restricted (typically the Catalyst) this fault may be the end result.

In my case it was a clogged pcv valve, cleaned it out with dishwasher soap, dryed it out and put it back on, after 2 weeks code did not come back.
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My son says it's driving better today. The pcv system is clean, I did the air vent pipe and related valves about 1 month ago, the pipes were pretty darn clean for a 13 year old.
Glad to know it is driving better, what did he do or it just went back to normal?
It just fixed itself :lol:

Today he said the CEL went off. Drives normal.

I got my fingers crossed, hoping by Monday it adds rubber to the tire tread depth and vacuums itself :rolleyes:
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