Hi, on olds threads i solve icp sensor problems and transmission problems.
i have a 1999 ford f350 7.3 powerstroke diesel
Engine is running good, idle is fine , but i drive another F350 like this and runs more powerful.
I have now P1248 code (Turbocharger Boost Pressure Not Detected)
also i don´t hear the tipical noise from turbo.
Today i take off the air filter and see that turbo suck air.
I also see that having engine running in park and accelerating about 3000rpm wastegate valve of turbo is not moving. i don´t know if this should move.
On google i see that probably this can be a turbo wastegate valve problem. but i don´t know how to check and if this valve must be move in parking or only with truck in motion. or.... do you have any suggestion?

 

Boost not detected means your PCM isn't monitoring any boost pressure. First thing to check is the MAP Sensor and make sure the electrical connector is seated properly. Then check the signal line (boost hose) to make sure it isn't broken or faulty.

If all that check out, then check your IC boots to see if they are secured properly. One of them could have popped off and that would also cause a no boost symptom.

Good luck.Attachment 36014

 

Thanks! great photo,
We are doing your tests now, one question , map sensor controls turbo boost or only check if is working properly?
I search several on google to find what is the function of wastegate valve, and don´t find a correct answer.
This controls the boost? or only send boost to exhaust when it have too much boost? must works always when throttle increase?

When you say to check signal line (boost hose) this is a cable that came from PCM right?, because from map sensor only came a tube that i think is vacuum or air.

Regards,

 

The MAP sensor is just a sensor. It measures turbo boost and reports the reading to the PCM. The PCM then uses that information and commands the other systems as necessary. If there is no boost, then the MAP sensor will tell the PCM there is no boost and the PCM will throw a code (which might illuminate the SES light).

The signal line is a rubber hose that is connected to a fitting on the intake manifold (commonly called the 'spider'). The intake manifold will be pressurized with air by the turbo under normal operation (boost). Since the MAP signal line is connected to the manifold (spider) then the MAP sensor will see the same pressure that the manifold (spider) sees. If that hose is cracked or faulty, then air pressure will escape and the sensor won't read it correctly.

Some owners add a boost gauge and tap off the MAP signal line with a T fitting. If that fitting is plastic, then it can break and throw the code you mentioned.

Another common cause for the same code is a leaking or popped IC boot. There are 6 boots to check. 2 on top of the engine, 1 each at the intercooler inlet/outlet and 2 more beneath the intake manifold (spider).

The waste gate is a safety valve of sorts. It's there in case the turbo makes too much boost and it bleeds off some of the extra pressure. You won't see it move at idle or even while reving the engine. Right now it won't function at all since you appear to not have any boost anyway. Don't worry about the waste gate, I am sure it's working fine so you shouldn't mess with it right now.

Find out if your MAP sensor is connected properly (electric plug AND the signal hose is connected and not leaking). If that looks good, then check your IC boots. If you don't see anything wrong then report back and we'll help you along from there.

Good luck.

 

Yes, the tube you mention looks like a vacuum line but it is actually boost. There should also be an electrical plug connected to the MAP sensor as well. I updated the photo to show you what I mean. Find that connector, plug it in and your issue should be resolved.

Hope this helps.

 

I've got an '02 that just threw this code. My truck feels like the turbo is still working. Where is/are the IC boots and the spider? the pictures help a lot!

 

The spider is the intake manifold. It's a cast aluminum part that clamps onto the compressor housing (the part with the black and green connectors and colored tubing...)

The spider has two 'arms' and two 'legs'. The 'arms' connect to the CAC (Charge Air Cooler) tubes which plumb to the cooler. There are silicone boots at each junction (qty 4). See the large hose clamp looking thingys....

The 'legs' of the spider connect to the intake plenum at each cylinder head. There are two orange boots down there as well. If those are loose, then remove the assembly and clean it so it's nice and dry of oil residue then re-install. Try not to tighten the clamps too much on the intake plenum side since those are made of sheet metal and crush easily. I usually use hair spray on the orange boots to avoid leaks down the road. (helps them to seal nice and tight...)

 

Hello everyone I have a excursion and around town I get about 19 pounds of boost but the minute I hit an incline I have absolutely no boost ive checked the boots connection to the map and the boost signal any ideas why im loosening the boost any help would be very appreciated thanks