HarryBiron093

Thank you all so much for the help !

Guys, I wanted to share that we solved the 3-4 code when it’s raining out. The wires going to the cam sensor had a short in them behind the valve cover where it goes over the bell housing. I had some good rain and was able to verify that was causing all the havoc ! Thanks to everyone that helped. The next issue is the engine hunts at idle, some days it does other days it dosnt. The passengers side fuel tank has air coming into it when the engine hunts. I assume the return is on that side ? Where would you check for air ? Plumb a clear hose in somewhere ?

That’s a great idea I will check the vecu tomorrow. I do remember there being dampness on the passengers side floor so I will see if I can replicate the symptoms.

Connections are all clean and there’s no resistance to the battery’s from any of the grounds.

My otter what did you find to be the problem ?

Do you think we are dealing with 2 separate issues on the 3-4 code one being when it rains and the other at high load high speed ?

I cleaned up the block ground and there was one on the frame rail right beside the block one that had 5 or so smaller wires going into it. I am not sure about the ground breaker on the firewall is it in the picture below ? When you say fuse panel is that the one on the top on the engine ?

Joe, I have not checked grounds out side of what the 3-4 procedure calls for. On the 9-2 code diagram where does it call out the locations of the grounds ? BK-u-2.0

Good morning, I wanted to close out and reopen some issues from last year. Any help as always is much appreciated. The a/c issue with the expansion valve freezing up… I got ahold of a guy at Red dot that was extremely sharp. After doing some testing he told me that the expansion valve on those could be put in backwards. Sure enough that’s what it was. A/C works excellent now. The 3/4 code got a lot better for the majority of the summer after replacing the front cover but under load at 60-70mph it still throws the code on and off with power cut out. Some days it builds really good boost 35-38psi other days it dosnt build past 30. The 3/4 code comes on with a steady light when it rains heavy at night or while driving the truck in the rain. I finally had a chance to troubleshoot via the service manual for the electrical part in heavy rain. I found no shorts or any resistance readings that were alarming. At the end of the procedure it says replace the ecm. I did last year send it out to get rebuilt. To recap what has been done already. changed the ep and Rpm/Tec sensor both and 2 times/ checked ohms checked with depth micrometer and at the suggested Mack levels it should need no shims in the timing cover for the sensor. If you start it like that the 3-4 code is immediately on and the truck cuts in and out terrible. It was like this when I bought the truck. Truck runs the best with 2 .30 shims and one .15. Still cuts out on the highway. replaced front timing cover. replaced clutch and while i was in there I verified flywheel to cam timing per the book. had ecm sent out and gone through for $800 has anyone seen the rain affect a truck like this ? I’m at the point where I am going to run jumper wires out of the ecm to the sensors or replace the dampener (it’s 460hp so it has the bigger one) or buy a new ecm does anyone have a test one I could pay to use ?

Yes sir when I popped the cover it was very clear lol you got it the information is much appreciated. Did you do much a/c work ? The symptom is vent temp is like 57 at best and low side is low high side normal. I’ve replaced evap/heater core/expansion valve/compressor/ dryer. Picture was at roughly 80degrees. I did loop my heater hose to make sure it wasn’t leaking by.

As always thank you very much for the reply. I ended up pulling the cam (the correct way) and found very minor wear on the thrust washer. I put it back together with a new timing cover/sensor etc. ive been chasing this vibration for a while now and I thought it was coming from the transmission but it got a lot worse last week. I pulled the drain plugs and the rear rear pinion gear was coming apart. I change the rear end and the truck is smooth as can be. Also my 3-4 code dosnt come on but once in a great while and it has excellent power. What are your thoughts on a driveline vibration amplifying that code ?

Thank you for the info !

I have 2002 RD E7 460. It’s been throwing the 3-4 code since I bought the truck 2 years ago. When I first got it there were no shims in the cam sensor. I replaced front and rear sensor. In order to get the light out and no stumble I needed 2 big shims and one little one. This year it needs another small shim to keep the light out. With this being said when it’s raining the truck runs worse but the code is never logged continually like a direct short. I sent the ECM out and got it rebuild with no help to the situation. I have verified via Mack Pro again thank you ! That my software is level 7 which is above the required per the service bulletin on the 3-4 code. I pulled the front cover today in hopes to find a worn thrust washer but I don’t see much wear on it. If you look at the picture youl see that it looks like the sensor is touching the the cam gear. Does the washer wear behind the cam gear where you can’t see it ? Anyone ever heated the gear and pulled it in place to avoid pulling the cam ? Help is much appreciated !!

I have 2002 RD E7 460. It’s been throwing the 3-4 code since I bought the truck 2 years ago. When I first got it there were no shims in the cam sensor. I replaced front and rear sensor. In order to get the light out and no stumble I needed 2 big shims and one little one. This year it needs another small shim to keep the light out. With this being said when it’s raining the truck runs worse but the code is never logged continually like a direct short. I sent the ECM out and got it rebuild with no help to the situation. I have verified via Mack Pro again thank you ! That my software is level 7 which is above the required per the service bulletin on the 3-4 code. I pulled the front cover today in hopes to find a worn thrust washer but I don’t see much wear on it. If you look at the picture youl see that it looks like the sensor is touching the the cam gear. Does the washer wear behind the cam gear where you can’t see it ? Anyone ever heated the gear and pulled it in place to avoid pulling the cam ? Help is much appreciated !!

What does the connector end up going to so I know it’s the right one ?

Yes the key switch will work the first time and then it will take 3 cycles sometimes.

I checked the ECU fuse and wiggled per Joe H with no luck of killing the engine. See below in the video with no engine light coming on. The idle surge is no longer as issue but thanks for all the input it just needed a set of filters. The big problem is the truck dying out while driving and then coming back to life. Since to lighting bolt isn’t currently available I don’t have another way to check codes do I ? V Mac3 I don’t seem to find this connector any other descriptors ? IMG_5520.MOV

Joey Mack this was the repair bill from the sensors. He told me they put the rear and front speed sensors in, nothing related to the cam or crank to my knowledge. I will check those fuses ! Thanks all

New to the form any help is appreciated. I have an 02 RD 688 with the 460. When i bought the truck it had the problem and i have chased it since. You will be going along and the tack will go to zero for a few seconds engine dies and then restarts. The local mack garage changed both speed sensors and over the winter i sent the ECM out thinking it that it might be that. I drove the truck yesterday and it still has the cut out. Other issues When you go to shut the truck off sometimes you have to turn the key back and forth a couple times before it shuts down. I have checked the wiring and replaced the key switch hoping to fix the issue with no success. Not sure if the 2 are related or not but any thoughts on this issue is appreciated. When you plug into the truck it had/has a code for the pyrometer. But there isn't an engine light on the dash. Mack said the bulb was missing but i pulled the dash and its a sealed unit