ALTITUDE PRESSURE SENSOR

[TWO_4_THE_ROAD]

Hello:
I have an 07 Chevy Duramax/Allison 2500hd. Last year while heading up to the High Sierras and pulling my 30ft 5er, the engine light came on. After calling On star it was determined that it was the Altitude pressure sensor that triggered it off. I waited a while on the side of the road because the truck lost power and went into a slow mode. After a bit, I started it up and it was fine the rest of the trip. When I got home, I took it to the dealer and they agreed that it was the sensor. They replaced it. The next trip, the light came on again when I started climbing and steep grade and it stayed on for a couple of hours. I got to my destination and shut the engine off. When I turned it back on, the light was off and stayed off. When I got home I called the dealer and they told me that they couldn't check the sensor unless the engine light was on. Not a comfortable feeling cuz I plan to go on a pretty long trip in August which I'm sure will involve some climbing. Does this sound right that they can't check the sensor unless the light is on?
thanks in advance

[Charlie_D_]

On a trip to Montana with our camper I had a CEL come on. Just outside of Billings. Stopped at a dealer and they read the code that said I had a glow plug bad. Knowing that it was an emission item I said and they agreed that I could continue. They cleared it but came back on some time later. They refused to accept payment. Several thousand miles later and at home the glow plug was replaced.
Not saying this is your problem but if the light is on and you are close to a town a dealer may do the same for you.

[mapguy]

NMDriver wrote:
That year(and some other years like my 08) of Duramax have a fuel line problem when under load at high temperature. You can read about it on the Duramax forum. link

Basically the rubber fuel hoses collapse due to the injectors sucking to hard. One cure is to get heavy duty hoses (the link provided solution) the other is to put a lift pump on the truck to feed fuel instead of having it sucked out of the tank.

The lift pump solution has other advantages for the injectors but is around $1000 pro install vs the better hoses are $100 if you DIY.

BTW: A code reader will likely say you need a new fuel filter or injector rail, or injectors. None of those are the problem it is low fuel pressure that causes the problem. I have a code reader and it kept telling me my fuel filter was clogged. It was not the fuel filter.

One word of caution about the fuel filter. If it was not installed correctly (gaskets pinched) you may be having a air leak and that too will cause the symptoms mentioned.

what code is popping? the fuel hose issue is the real deal and can have an effect on your injection pump (CP3)lasting. their is a TSB for the collapsing fuel lines. collapsed fuel lines cause the CP3 to work extra hard/get very hot.

[Drew510]

Might be worth checking, but I had a similar issue with my gasser. Last year when pulling grades, the CEL would come on and then go off after about 50 miles past the grade. Turns out it was the MAF. Replaced it and no more CEL.

[BarryG20]

This is probably not your problem but on my old 96 gas ram truck If I went over 12k in elevation the check engine light would come on (i know very few roads get that high but I found a few of them here). So I take it in they do this that and the other. Every time I went on 2 specific roads the light would come on. Finally one of the techs got to the bottom of it. The ecm was not calibrated/mapped to run that high of elevation. Probably more specifically that low amount of air/02 So when the truck sensors sensed the lack of air it no longer had a fueling map to go from the truck still ran ok just the check engine light would come on.

[NMDriver]

That year(and some other years like my 08) of Duramax have a fuel line problem when under load at high temperature. You can read about it on the Duramax forum. link

Basically the rubber fuel hoses collapse due to the injectors sucking to hard. One cure is to get heavy duty hoses (the link provided solution) the other is to put a lift pump on the truck to feed fuel instead of having it sucked out of the tank.

The lift pump solution has other advantages for the injectors but is around $1000 pro install vs the better hoses are $100 if you DIY.

BTW: A code reader will likely say you need a new fuel filter or injector rail, or injectors. None of those are the problem it is low fuel pressure that causes the problem. I have a code reader and it kept telling me my fuel filter was clogged. It was not the fuel filter.

One word of caution about the fuel filter. If it was not installed correctly (gaskets pinched) you may be having a air leak and that too will cause the symptoms mentioned.

[darsben1]

Buy your own reader and read the codes when it happens. Write them down and take them to the dealer.