P 1251

willie · **Posted:** Wed Jul 29, 2009 9:26 am

The engine light came on this morning, the code is P 1251.
Does anybody know what this is?

ATXKJ · **Posted:** Wed Jul 29, 2009 9:34 am

http://www.lostjeeps.com/forum/phpBB3/viewtopic.php?p=286960#286960

gmctd wrote:

Vacuum should be ~26", measured with a vacuum guage, rather than a designated finger

P1250, 1251, 1252 is vacuum reservoir errors - check out the wiring, connector, and possibly the solenoid, over between the fender and the airbox

Vacuum problems = Boost problems

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

P1251 is the intake vacuum reservoir short circuit to ground.

Did you lose performance with this code, i.e. is the engine not building any boost?

This is an on/off solenoid that is supposed to power on with the key in the run position and off with key off. The unit was designed to keep vacuum stored in the vacuum reservoir overnight to have enough vacuum to power the turbo after a morning cold start. If it has failed closed, as it did on one of our test vehicles (no vacuum allowed to turbo and no boost), you can just unplug the vacuum supply line from the engine that goes to the reservoir/on-off solendoid and plug it directly into the EVM that controls the turbo. The turbo EVM has a little dust element on the bottom side, in order to be able to tell the difference between the two solenoids. The turbo EVM has two ports, one labeled "VAC" and the other "OUT". Engine vacuum line should go into VAC and the OUT is the line to the turbo.

This is a fix to keep the engine making boost and you can get a new IVS at your liesure.

nursecosmo · **Posted:** Wed Jul 29, 2009 6:31 pm

P1251 is usually accompanied by a P0299. It may be that your vacuum reservoir solenoid is failing in the open position. Try a little test. After the engine is off for a couple of minutes, move your vent selector to a different position and listen for a hissing sound. If there is no sound, the vacuum reservoir can't hold a seal because of the open valve.

willie · **Posted:** Wed Jul 29, 2009 7:48 pm

Thank you all!
I did not loose performance, I also checked for the hissing sound while changing vent setting (engine off), the sound was there.
So, I cleared the code and hope for the best. If the code returns I will use your suggestions.

P 1251

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