Mackpro

As Vmac3 mentioned, there are very specific sealing procedures when putting a head back on a MP engine. On the upper rear timing gear cover. The early ones were aluminum and were good. Just change the rubber gasket and all is good. The newer covers are plastic and junk. I replaced the whole cover every time because they warp and leak. Also using the hood down tool that pushes the cover down while you tight the screws is a must

it’s worth a shot.

This is really a hard one as all the start relays go back to the trans ECM that is no longer there . Somewhere there is a Relay #20 ( Mack doesn’t say where) start enable relay. It doesn’t show up on any of my fuse box diagrams. There is also a relay usually mounted on the outside firewall labeled MEIIR, I was hoping jumping this relay would work but it won’t as it goes back Trans ECM. The trans ecm powers up 2 relays sorta in line , the hidden relay 20 and the regular start relay #36 that in the fuse box by the clutch pedal. The main goal is to get 12 volts on wire CB28A at the VECU connector B pin 28. You also have to put 12volts on the CB28B wire at relay 20 which will feed back and engage the regular start relay 36 . Be very careful with relay 36 it can be turned and inserted 90 and it will never start .

I’ll see in the wiring diagrams for a 2012 Auto shift if it’s a simple jumper harness added in like the older CXN and CHN’s

The engine ecm controls the ground for that small solinoid on the starter. The engine ecm looks for the start signal from the VECU, which is looking for a neutral signal from the now missing trans ecu . The VECU can be reflashed from the dealership to a manual trans. Years ago Mack would not this on the 2008 and up trucks but a couple years ago they said they would. Removing the Auto shifts and Ultra Shifts in the older grey engine trucks was easy to by pass all the wiring . Not so sure on these MP equipped trucks

There was a software update for the EGR cooler efficiency code some years back . You can remove the hose and elbow on the front of the cooler and blow it out with blow gun . Wear a mask because black soot will fly everywhere. Then replace the EGR temp sensor and clear code . I’ve had decent luck doing that when replacing the EGr Cooler wasn’t option due to parts availability

Mack really does not recommend this but you can have the axle bent to get the camber right . A local heavy duty alignment shop here does it.

As in exhaust flow abs pressure through cooler ?

Your engine software is a Step 5 and Vehicle software is step 12b so your in good shape there . That’s the newest you can get .

What’s the model and last 6 of Vin and I can have my guy see what software levels are in it

If you got that high of exhaust temps then possible boost pressure leak. While the AI engine is fairly reliable, 4.3 MPG was the usual average of all my buddies CV713’s . I always drove them with throttle pedal to the floor, loaded or unloaded. Does it have a turbo boost/manifold pressure guage in the upper left corner of the dash?

Unusual code . Check the 3 connectors on the back of the dash cluster for pins pushed out . Has the cluster been replaced? This code is commonly seen inactive after doing software update on the cluster. Cluster possibly out of another truck/wrong part number. Unhook any Qualcomm or data loggers that are on any of the data lines.

The very first one box systems had a few issues but they changed the DEF doser gasket/insulator and that seemed to solve the issue. Had a few DPF filters crack in the early ones too. Our oldest one box system truck is a 2017 with 400,000 miles and just replaced both NOX sensors this week for fault codes. However now it has codes for pumping injectors/ camshaft lob slip. Which might be the cause of the NOX codes. All one box system trucks are common rail engines

That’s awesome! We always try to do a 45 minute test drive at highway speeds on SCR issues. After 45 minutes, plug back up and check codes . Just because lights are not on the dash doesn’t always mean there are no codes pending

I believe the PPID 270 is inlet nox sensor code. The PSID 46 I’m not sure on .What’s model and last 6 of vin

The minimum efficiency is 80% , it logs the last 5 efficiencies test . If the last 5 are below 80% then it’s a ongoing problem

You getting the dreaded P20EE code?

On most models , using Tech Tool you can do a Nox conversion test or a regular regen and watch the nox levels when DEF fluid is dosing. Nox inlet will be high of course and the outlet will be much much lower. Mack never told us that the levels should be though

I even pulled the blue prints of the MRU wiring diagram and it doesn’t show it . But from the looks of the diagrams , the air intake heater and turbo actuator are related in wiring

You have a model and last 6 of vin and I can run it through tech tool . It’s the low speed data link for the dash cluster

The Mack diagrams are so screwed up I can’t find the fuse number. Do you have a fault code ? The only way I can trace it is through tech tool

Yes , when the CX first came out in 2000, the ones with 427 and 460 HP’s were running hot. SB-232-016 bulletin that came out in 2001 showed part numbers and how to install the low mount kit. Only the very first CX’s needed the kit. By October 2000 it was standard on all the CX’s.

A bad starter drawing to many amps could the the cause . Of course start by charging each individual battery separately and load testing . Them move on to the battery cables and grounds . Engine to frame ground on driver side frame rail. The ground breaker and auxiliary starter solenoid by the wiper motor on the firewall under hood . All need to be checked thoroughly. We were lucky and the shop had a large battery and starter tester and could measure starter draw when starting. It measured up to 1400 amps. We had a few bad starters they maxed that reading out . The draw was so high that it took so much voltage away from the engine ECM that it would not fire the EUPs and the engine would not start. The owner was convinced it was a fuel issue because you could use starting fluid to get the engine spinning fast enough that it took the load off the batteries and the engine ECM had enough voltage to then start running. Acted just like a fuel issue. One way to check with out a starter amp flow tester is to use a volt meter and check voltage at the fuse of the engine Ecm on the fire wall while cranking . If below 9 volts then you got voltage issue. You can also check the same way on the VECU fuse in the fuse box inside the cab .

Around the same time we were having EUP bolts breaking a lot. The angle drill was helpful on thoses too. Of course another service bulletin on updated EUP bolts came out soon after

Very very possible. We had so many bolts breaking back then I bought a angle drill so I wouldn’t have to pull the water pump housing off . The lower driver side bolt always seem to break when removing if not already broken.