P0234-Over boost and derate

OHNO60 · April 23, 2014

Any of you guys ever run across a P0234-over boost on a chassis cab that's intermittent? Freeze frame shows mostly around 1500 RPM flag and after road test of 75 miles cannot duplicate. Release to customer and like clockwork flags a derate. TSH useless... OASIS nothing...Ran PPT and all readings match. :banghead:

Keith Browning · April 23, 2014

Does the freeze frame data show the boost reading?

Brad Clayton · April 23, 2014

Not sure if boost is in there but I think the map reading is and boost can be calculated by subtracting baro from map.

Steve Mutter · April 24, 2014

Have you removed the map sensor to check the port to see if it is plugged with carbon.

lmorris · November 13, 2014

I have one in right now. PPT finds no issues. MAP_A reads 41.8 PSI, with BARO at 13.7, that puts me at 28.1 PSI boost. Steady cruise at 100 KM/hr. EGT readings are around 750 F, datalogger shows 110KM since last regen completed. Regen was inactive at time code was set. MAP is plugged with soot. Going to clean and see if truck returns.

tonybullitt · November 19, 2014

Imorris did cleaning the map make a difference? I have a 13 cab and chassis doing same thing npf send a guy out to test drive and it acts up on him.

lmorris · November 19, 2014

Imorris did cleaning the map make a difference? I have a 13 cab and chassis doing same thing npf send a guy out to test drive and it acts up on him.

As far as I know it did, been almost a week and they haven't come back.

tonybullitt · November 20, 2014

Thanks I cleaned and had truck driven it reset the code again. I have a turbo ordered.

tonybullitt · November 21, 2014

Had another f550 come in today. Passes ppt ka but resets code.

tonybullitt · November 21, 2014

Turbo is in first truck. Not setting overboost code any more. i made some recordings with new turbo taking off from a stop wot onto interstate to 75 mph. I went thru recordings and highest i see map getting now is 42 psi with a baro of 14.2 gives me 27.8 psi boost. Hotline told me cab and chassis normal is 22-28. With the old turbo it would peg the map at 50 psi at times.

tonybullitt · November 21, 2014

Ordered turbo today for second truck also.

tonybullitt · November 26, 2014

Turbo fixed 2nd truck also.

lmorris · March 17, 2015

So I have one here, F550 with 52000 KM on it. Tuned, exhaust delete and aftermarket air cleaner. Driver says it only sets when he is running out to job sites and has to clear the code to get it out of derate, so I have no freeze frame data to look at. Max boost I get is 26 PSI on hard accell up a hill. Map sensor is clean, and VGT seems to be operating ok. Tuner has turned off the EGR so I am not sure what affect that will have on the turbo as far as controlling overboost. Going to let it go for now with instructions to driver to record as much info as he can when it sets.