P0299 code.... under or over boost ?

Dennis MacGyver · **Posted:** Sat Sep 01, 2012 9:15 pm

About 300 miles on my GDE Eco tune, now this: CEL code P0299

This list says the P0299 is an under boost condition:
viewtopic.php?t=25049

While this code P0299 says it an over boost condition:
viewtopic.php?f=98&t=40073&hilit=p0299+B10b3

Maybe we should take a vote consensus.....WTH ??

Dennis MacGyver · **Posted:** Sun Sep 02, 2012 12:20 am

After doing some more searching here, I read that a disconnected vac hose to the vac center can cause a P0299 code.
viewtopic.php?f=5&t=64854&p=715396&hilit=+code+p0299+#p715396

Since I had just moved my vac center back a little to make room for my Mann ProVent 200 (straighter shot to the CCV and Intake hose) that's exactly what it was, a disconnected vac hose to the turbo.

Still doesn't answer the question of the code meaning though, high or low boost?

Billwill · **Posted:** Sun Sep 02, 2012 4:29 am

Dennis MacGyver wrote:

After doing some more searching here, I read that a disconnected vac hose to the vac center can cause a P0299 code.
viewtopic.php?f=5&t=64854&p=715396&hilit=+code+p0299+#p715396

Since I had just moved my vac center back a little to make room for my Mann ProVent 200 (straighter shot to the CCV and Intake hose) that's exactly what it was, a disconnected vac hose to the turbo.

Still doesn't answer the question of the code meaning though, high or low boost?

The code should really read something like "Malfunction of the Boost detection"

A lot of the codes are like this...when you get into the FSM you will see a whole host of potential problems for one code....shorted out, open circuit, too high, too low, erratic etc.

It just points you in the right direction and then assumes you have the factory scanner to take further readings

GreenDieselEngineering · **Joined:** Sun Jun 07, 2009 5:10 pm **Posts:** 1111

P0299 is an underboost and P0234 is an overboost. No vacuum to the turbo will definitely lead to an underboost code.

SLS · **Posted:** Thu Sep 06, 2012 12:26 am

This may not be exactly you problem but it is probably close & related to the turbo. Some have just had the hose come loose.

If you just found a hole in your inter-cooler-air-charge inlet turbo hose like I did at 130K+ this is a big help. The Jeep CRD lost power and made a noise from the engine that sounded like an air valve opening. I got a code P0299 - turbo underboost & I noticed oil spray around the coolant reservoir. It sure makes you realize what a difference that turbo makes.
After I found the hole my Forum search brought me to this very helpful piece.
http://www.lostjeeps.com/forum/phpBB3/viewtopic.php?f=5&t=51797&start=120

UFO · **Posted:** Thu Sep 06, 2012 5:44 pm

After searching this code here, it sounds like the MAP sensor can cause this as well, or is there a specific code for the MAP sensor? When I first got the CRD, I pulled and cleaned it, it was nasty and crudded up. Then I put on a SEGR.

Now I am getting the P0299 code consistently. I pulled the MAP sensor and it appears to be in good shape. Cleaned it but the code keeps returning. New sensor? Anyone used the Airtex sensor? I found it at RockAuto for $37, not a bad deal if it's a quality part.

Dennis MacGyver · **Posted:** Thu Sep 06, 2012 7:39 pm

UFO wrote:

I found it at RockAuto for $37, not a bad deal if it's a quality part.

Buy quality... >>>http://www.summitracing.com/parts/BCH-0281002437/

P0299 code.... under or over boost ?

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