DTC 48 - Air Intake temp to low

[bbudus]

Ok, so I have been dealing with a overheating problem, you can read that in my other thread. While I was test driving(after replacing the thermostats), the truck "burped" on acceleration. SES came on, truck still ran, and didn't really feel any different.

Let it cool down, pulled the connection the the air intake sensor, was a little wet, so i WD-40'ed it,and blew it out with compressed air. Reset ECM. Tried to start. Was very hard, but started, SES came right back on.

Yesterday went and purchased a new sensor from NAPA, thinking the sensor went bad. Truck would NOT start. So, hours later, battery charge engaged, truck finally started to come to life, lots of smoke. Hit the glow plugs for another 10 sec, and viola truck is running.

But my god did it rattle, clank, I was for sure something was either coming out the top or the bottom end. And that damn light came back on....DTC 48. Any ideas?

Thanks,

Bbudus

[JohnC]

My guess is you have a break in the wiring for the intake temp sensor. PCM thinks the air is -40*...

[bbudus]

Well, I replaced the sensor...twice. Still pulling the code 48. Fluked the hot and getting 4.8v, which is right, manual says 5v. I cut the ground wire and hard wired it to the block. I also pulled the new sensor and checked it for resistance, it is working properly.

So I am at a loss here. Sensors good, ground is good, hot is good, DTC 48 is bad. Truck is so loud, like ear plug loud, it clanks that bad. When you drive it feels like it is in limp mode. No throttle response, and misses quite a bit.

When I replaced the heads, I made sure to clean all the grounds, fixed all loose connections and tested all the wires before it was re-assembled. Could I have lost the ECM?

Thanks,

Bbudus

[JohnC]

Any chance you have the sensor wiring switched with something else? Do you have a scanner?
If you answered "no" to both questions, look real hard for a path from the "hot" wire to ground. also, try grounding the sensor ground to the ground cluster at the right rear of the intake manifold. That's where all the ECM grounds go.

[bbudus]

Well, I know I hooked up the correct connection, cause I am anal, and not only took pictures but used labels on all connectors. I don't have a scanner but have access to one and will be using it this evening. I also was talking to Bill Heath about the over heating issue, and at that time he told me to move the grounds to back side, passenger side head. Which was done. The reason was this was a better block ground.

After my inisial post, I pulled the codes again, now I also have a DTC 19, which would explain the missing and no throttle response, so I am in the process of removing, and testing the crank positioning sensor.

I am beginning to think that maybe there is a larger ground issue at work hear as it seems odd to be popping all these sensors at once. I did the battery cable mod, using 2 aught welding cable. This thing is grounded better than a sherman tank. And like I said before all connections were tested, etc... before reassembly.

Hopefully the scanner will reveal some hidden gem.

Thanks,

Bbudus

[rameye]

Has it ever run nice and smooth and started properly since your overheating incident???

I've been following your posts.

Sounds like you're entering the twilight zone!

[bbudus]

Rameye: It ran fine, minus the dtc 48, before the head gasket replacements. Now the dang crankshaft positioning sensor had to come out in pieces.... Total PITA....first the mounting bracket broke off the sensor, then the wires came out. Pliers you ask? No, that didn't work either. So, I drilled a hole down the center of it, and threaded a tapcon in, grabbed it with pliears, and had the truck rockin back and forth...thought the engine mounts were going to give...finally had to drill holes in it and take it out in pieces. This truck is truly lucky I enjoy driving it, or off with its head!!

Get the new sensor tomorrow, so we'll see.

Bbudus

[JohnC]

This truck is truly lucky I enjoy driving it, or off with its head!!

You already did that!

[rameye]

I never had to do one of those...it looked damn nasty (hard to get to)...I'm changing motors in a couple of weeks..I'm sure more tales of woe to follow.

Good luck, drop us line when you get it back together.

[bbudus]

It's ALIVE!!! For the love of mercy, I can't believe it. Had to wait for my buddy to bring home his camera; needed to make sure no big pieces of the sensor fell into the timing chain sump. I could think of all kinds of bad things to do with that camera, apparently he noticed the look in my eye and promptly took it with him.

Good news no chunks of plastic, finally put it all back together today. It is not really that bad once you take the power steering pump off. Unplugging and plugging it in was much worse, as the connection sits under the intake manifold by the IP.

My guess is that the ECM must look at both the intake air temp and also the crankshaft positioning sensor and if one is off it freaks out. My thinking on this is that low and behold, once the CPS was replaced no more DTC 48.

Truck runs normal, it runs cool, it has heat...knock on wood, but i think we got it happy again. Thanks for every ones help, and I hope that my experience will help somebody down the road.

Good luck with your engine swap Rameye, my only advise is if it looks like a PITA, change it while you can get to it... I learned the hard way:)

Bbudus