Mackpro

i would unplug the sensor and see if the FMI changes from 2 ( data erratic)to 5 ( open circuit). If the FMI stays the same its the harness or connector ( my guess) . If the FMI changes to 5 then plug the sensor back up and clear all codes, with the key on/engine off does the code come on? Does the code come on after first starting up or do you have to drive it under a load to get the code to become active?

Here is a code listing and possible cause's for 2010 SCR engine's, your code is in there and shows possible causes. 2010 fault code list.pdf

Here is the sensor part# listing and location for most all 07 emission (non-SCR)MP engines sb273014.pdf

I was wishing you had the new style turbo too, but when they do replace it you will have the newest style turbo they make. They started with the 631GC5176BM**, then upgraded it to a 631gc5176CM** then a DM** , so atleast you should get the newest thats available.

Going to M-Drive class in the end of October in Atlanta. It's only a 2 day class and most everyone here at our shop has done been to it. I know anything more than a top cover, ECM or output shaft seal and you replace the complete unit. No tearing it down as of yet.

The one you want to replace is the one that is mounted directly on the intake manifold. But to be 100% sure of the part # of the sensor, I need to know the exact model of the truck , CXU, CHU, GU, MRU or LEU. But If yor truck dosent have SCR/ Diesel exhaust fulid injection, the part # of the sensor you need should be #20524936.

If it is an MRU with an MP7, there are 2 sensors on the intake manifold, they both look exactly the same, the one towards the rear and mounted directly on the intake manifold is the boost temp sensor and thats the active code your getting. The part# is 20524936. The one mounted towards the front or on the intake maifold piping is the boost air pressure sensor. Same sensor part# is the same.

Forgot to ask , is it a GU713 or a MRU or what model?

When you change most anything on the engine you should do a "learn data reset" in VCADS. Whats the last 6 of the vin and ill look it up.

If the FMI is 5, it's an low voltage/open circuit . Make sure you have the correct sensor as the boost pressure sensor on the 07-09 DPF only engines are different that the ones on the 2010+ DPF/SCR engines. On the older MP engines the sensor is boost pressure only on the newer SCR engines its boost pressure and temp sensor all in one. They look exactly the same and will plug up but will derate and make codes appear.

The "burp" was on the first orignal 2004 ASET turbos (631GC5171 series turbos) . The very first MP-8 turbos habe the same issue as well , a software update solved the MP-8's. When replacing the old style ASET turbo with the new style ASET turbos (631GC5176 series) there was a software update that should have been done. Pull the large hose on the front of the EGR cooler off ( going to the "S" shaped pipe that goes over the engine) and check for wetness/antifreeze. If dry its ok. The EGR valves on the early ASET's would sometimes break inside and cause EGR flow when there should be none but this would usually set a code for EGR issue.

I wonder if the VGT/wastegate is sticking. Take the stainless braided air line off the turbo actuator (VGT/wastegate) and lightly blow air into the wastegate and see if the rod moves down full stroke then springs back up when air is removed. The pivot pin can sieze up and the turbo will not work correctly. The pivot pin can be removed and cleaned and coated with hi-temp anti seize. An "E" clip holds it in. You might have to shoot a little air in the VGT to get the pin in and out. Dont put to much air to the VGT or you could blow the diaphram in it. I dont think the lower HP engines had the boost pressur relief valve in the intake manifold piping.

There is sometimes a "L" shaped bracket that goes from the cylinder head to the water pump housing. If this is missing it causes the assembly to vibrate and crack the water pump housing. Last 6 of the vin and i can maybe get u a parts pic and see if it wass equipped this way.

Our sister store sold a local fleet 15 CXU's with the MP8 and M-drive's. All the top drivers who are mostly oldtimers did not want to get out of their older CXU's with manual trans and climb into the new CXU's with the M-drives. Lots of bitching and groaning but the boss said just try them for a week. I not lying but the owner of the company/fleet said after a week , 100% of the drivers said to pass their older trucks on down the line and that their not giving up their M-drives. We have had no failures of any kind with the M-drives. I know one very very large dealership that had to replace 2 but it was by Macks request and just a drop in the bucket of the number of M-drives he had running around there.

Look at the tag on the turbo and see if the part# ends in something like 631GC5171M***. Hopefully you have the newer 631GC5176M** series turbos. The 5171 series had some weird issuses with them. You rarely see them much cause the had a high failure rate and probably have all bee replaced. Check for soot leaking around the exhaust manifolds and the EGR piping as the EGR piping actually had turbo boost pressure on it when under a load. Make sure this thing doesn't have an exhaust brake on it under the cab. Check the muffler for a broken baffle , rattling around and sometimes blocking air flow through the muffler. 8-3 code is the #3 EUP pump and shouldnt cause the noise and whistle issue.

If under warranty send it to the dealer, otherwise throw parts at it. Extended warranties dont sound so bad after all (with these new engines). There are no troubleshooting books on the 07 emission MP engines and newer. The only troubleshooting guides are in the VCADS/PTT software that u can buy from a Mack dealer and put in your laptop. Sadly, with the MP engines, we dont even try to "fix over the phone" as it would take hours to explain and then without all the special tools and breakout boxes your wasting your time. With the older engines we could scan and fax pages out of the manual to the customer and help him that way but with the new stuff its impossible. By the way whats the FMI of the code and does the engine have SCR/ DEF injection on it?

Low coolant sensor fault, with the FMI of 3 its probably not low of coolant but looks mor like a electrical/ wiring issue or a bad sensor. Unplug the sensor and put a paper clip jumping the two wires together and see if the light goes out, hopefully it does , if not unplug both engine ECM connections and check for oil or antifreeze in the engine ECM and harness.

On top of the dash in the fuse box look at fuse # FU53 its a 10 amp and powers the compressor. Also fuse # FU72 powers the complete AC/heater unit. And also check FU25 as well ( its a square shaped fuse )

My buddies 2012 CHU daycab with no fairings, 505 HP, Mack 10 speed trans, rear gears are in the 3.40 range ( cant remember) just pulled a loaded van back and forth to StLouis at 68 MPH and he got 6.8 MPG. Boss man said he heard of MP-8's with super high rear gears running 13 speed trans and mostly running in 12 th gear but on flat ground going to 13th gear and the engine RPM dropping to 1100 RPM and getting some unheard of MPG. Not saying its true but thats what I heard.

The last RD688S I can find was built on 4/7/03 and labled a 2004 model. It did have a AI-350 ASET engine in it. However some of the other guys may have a better way of looking it up in the Mack mainframe.

I have seen alot that average 6.9MPG with and without wind farings. Keeping the MPH down is the key. None were equipped with a 13 speed though , Here we rarely see a 13 , 15 or 18 speed trans anymore unless in a GU.

Looks like on 4/12/11 a Mack dealer set up the step 12B downloads and new datafiles for the engine. Its shows the dealer downloaded the new files in their laptop but the dealer didnt send back the confimation file saying they were installed into the truck. Not saying the dealer didnt install them but who knows. It shows u have a fuller 8LL trans and 4.42 rear gears. Truck came with 22.5 wheels but no tire size listed. If your running full size 24.5 tires they might be to tall for your 350 HP. We sold 2 CV's with 400AI's, 8LL trans, 24.5 tall rubber and 4.17 gears. Almost had to buy them back from some very unhappy customers. The AI engine has a very tight window for every thing to work right. Any one thing out of wack/changed and its low power complants. The good thing bout the AI engine is to do HP upgrades you just need to change turbo and injectors and download. Older ETECHs you sometimes have to change the camshaft keyway. In your case you might need to upgrade to a air fanclutch as well.

S Here in the States the CCRS 460 has a wategated turbo and if you try to change anything or adjust the wastegate for more boost it will derate the engine when it overboost's past specs. The 427 HP CCRS's dont have this feature or the high$$$$ wastegated turbo. When customers come in for factory HP upgrades on a CCRS we usually steer them towards the 427 for this reason. We have actually turned a 460 down to a 427 due to the customer always swapping custom turbos and injectors.I saw a Detroit 60 series wategated turbo bolted on the exhaust manifold one day on that truck.

We only use Panasonic tougbooks in our shop. They are worth the money if they are used every day by different techs, They get rained on, dropped on the floor, oil spilled on them and thats on a good day. We have the Cummins Insight program which is awesome and of course the Mack/volvo VCADS/ PTT ( which everyone here hates with a passion) and we still use the old Mack software alot. For other trucks we use the Eaton MD-300 which works well on other makes and models of truck and engines and ABS.

If the FMI is 4 that means voltage low or open circuit. If your engine ECM is mounted up on its edge on the driver side of the engine, pull the top/J1 connector loose and check for antifreeze or oil in the connection. Wire number for the # 4 eup are EJ1-24-2.0 and EJ1-41A-2.0 . Which would be pins 24 and 41 in the engine top/J1 connector.