tool

So I keep throwing an overboost code P0234.

Scan it, check the freeze frame data, says I am boosting 75 IN HG.
which is like 36 psi I figure o.k, time to change the MAP sensor, must be crazy.

Go to Cummins, get a MAP, change it, still throws the code.

So I figure must be something electrical somewhere, I fiddle around tonight and hook my mechanical pressure gauge setup up (the same one I use to check fuel PSI) I couldn't find my teflon tape so I was probably actually loosing a little pressure and I could hit like 25 PSI without too much trouble.

What could be causing this???

Obviously the wastegate isn't doing it's thing, must be siezed I guess. But when boost gets to 20 psi shouldn't the thing defuel and not boost any higher????

This has me puzzled.

Any ideas???

mikelr

I say get a boost fooler (like an Edge EZ) and roll with it.

Ram2Pete

I second that

RustyJC

A sticking wastegate or a plugged, cracked or broken hose from the turbo compressor discharge to the wastegate actuator can cause overboost.

Rusty

tool

If the ECM is supposed to defuel at 20.6 PSI how can my truck continuously make 25 PSI????

Does this condition help or hurt the performance/mileage of my truck?

What affect does the P0234 code have on the running of my truck?

HOHN

Your signature indicates stock fueling. Do you have any performance chips or modified injectors?

If not, then you should NOT be able to make over 25 PSI, even IF the wastegate was seized closed. The ECM should defuel.

Maybe a leaky injector is allowing too much fuel?

Maybe a bad MAP right out of the box? (not likely)

Maybe there's a restriction in the exhaust somewhere?

jlh

andyt

My truck makes about 28 psi with no fueling upgrades. I have the hose that controls the waste gate disconnected and plugged. I did this to try and get a little more power from it. Above 20 psi I can feel a little extra power. Truck has been this way for about 30,000 miles and have not had any kind of problem and no codes either.
Andy

tool

Yes my truck is stock, no fueling mods. How would I find a bad injector without a flow bench or some way to test injectors?




I can't see how you can make that much boost andyt without a boost fooler of some kind and not throw a code. Mine sets a code all the time.

Are you sure there is no code??? Have you had it scanned?? I don't think increasing the boost pressure is going to make you any more power unless you increase the fuel as well.
The overboost code does not set the Check engine light so unless you have had it scanned, I'd bet there is a code there.

gamiller31

I have RV275 injectors w/the wastgate disabled. I can easily hit 30psi boost, and routinely hit 25psi on uphill freeway entrance ramps. I have yet to experience defueling, it pulls real strong, all the way to 3k rpm. As long as it continues to not defuel, I will leave it as is, unless you guys can tell me that I am messing something up.

tool

Have you pulled the codes gamiller31????

Surely you must have a code if you have no boost fooler.

Does anyone know what affect the p0234 code has on the operation of the engine??

IE. does having the code present change the way your truck runs?

phox_mulder

One way is to get an infrared thermometer and check the output of each cylinder.

There shouldn't be much variance between them, if there is, that would be the bad injector, either sticking open or closed to long.

1 bad injector wouldn't do much to the boost level though.


phox

gamiller31

Have not had the codes pulled, but have never had the CEL come on. I am not the original owner, so if it has a boost fooler, I am unaware of it, and do not know what one looks like. Could also be I have a bad MAP sensor, cause my truck will pour black smoke when go pedal is on the floor, but only when it is on the floor.

tool

Overboost code won't set the check engine light. (atleast it doesn't on my truck) I'm not the original owner of my truck either so maybe someone fiddled with the waste gate or something and had a fueling box on it at one time???? Hard to say.

Beast2B

I was under the impression that when it's IN the overboost condition, the engine will run in limp mode, basically feels like 1/2 power and sluggish. I've felt limp mode before when my Comp ground lead (my bad connection) caused some codes and a CEL, but it doesn't sound like these trucks are going into limp mode...
Without any added fuel from a box I can't imagine you'd get too much gain other than high EGT if the boost gets above ~35 psi

tool

I think your gain would be negative actually.

here is my logic;

Under normal conditions as boost approaches 20 psi, waste gate opens, dumps boost, boost stays below 20.6, ECM is happy and keeps fueling.

With sticky waste gate or whatever is causing this, boost clears 20.6 ECM backs out of the fuel to lower boost????

That's my logic, yet obviously I'm getting enough fuel to clear 20 psi.
Truck runs strong, probably would not know code was there unless you pull it with a scanner......

I started to investigate this because of heavy idle smoke.