Mackpro

RH Sheppard has all their manuals on the website. I use it a lot . TRW used to have their manuals online but haven’t checked it a while. First thing would be to figure out which brand then which model gear box you have .

RD690P built 10-12-94 with a mechanical EM7-275 HP engine . 217” wheel base , 12,000 pound steer axle , spoke front and rear hubs, 5.02 Mack rears , Mack 5 speed trans T2050, spring rears but not camel backs .

https://www.bigmacktrucks.com/topic/29716-low-boost-wastegate-error-code-can-anyone-help/

Mack has a good bulletin on the 4-5 code on the CCRS 460 engine. Only the higher HP levels CCRS engines used the wastegated turbos. Not to be confused with the ASET 4-5 code with the VGT turbos . On the CCRS 460 , in the engine software there is derate for overboosting and if the boost is to low then of course you have low power. So the wastegate adjustment has to be set up perfect. I’ll see if I can find the bulletin

https://www.bigmacktrucks.com/topic/48125-scr-fault/

Mack had some good service bulletins on this code but they seemed to have disappeared . I’ll see if I can find a link to them

Looked up in my chart , the 380/410 and 427 are exactly the same . Same turbo and injectors ect. The 380/410 puts out 1660 foot pounds of torque , the 427 puts out 1560

The cam key way swap was only on the early Etech engines . 1998.5 through around 2001.5. After that the CCRS ETECH engines came out and from then on no more cam key way swapping

They should be pretty close to the same thing . I have a chart at work that shows part differences in HP versions . The only differences in the AC engines are turbo and injectors. Of course the engine ECM stores the HP setting as well .

A bunch of bulletins released today on CBR , CBR-2076-1 talks about new software for the P20EE code . Unknown how long the software has been out but it’s worth a try .

Check the fuse panel by the clutch pedal for water damage. Pull one of the bottom relays out and look for while crusty corrosion. There was a recall for this on some units . Follow the battery cables all the way to the starter . Look for them rubbing the frame rail or transmission. Check the ground lug welded to the frame behind the battery box. Is there any GPS/data logger/Qualcomm hooked into the diagnostic connector? We had a faulty Qualcomm cause lots of issues till we unhooked it . Check the terminal strip by the fuse box on top of the dash , there are a few ignition, battery and ground connections there , also 2 data link terminals, make sure nothing is touching them . We had a guy hook a CB up and his power wire terminal twisted over and touched the data link terminal causing a problem that took a day to figure out .

I think in the last CBR bulletin I saw, it wanted you to look at the past history of the truck , like a failed turbo or EGR cooler . Where oil or coolant could have made it to the DPF or SCR box. This could “ poison” the SCR box. Software updates help sometimes . We have been lucky and have not had to replace any SCR boxes on our 30 CXU/Anthems yet . We did have a cracked DPF filter causing a P20EE code once , see if the exhaust stack black or clean

There is a fuse for the turbo , I can’t remember which fuse box it’s in though. Also, other sensors on the same 1939 data that the turbo is on could be shorting out causing the issue. On some year models the DEF level sensor is on the same data link as the turbo. Make sure your DEF level guage is working

I remember having lots of issues with a certain emission year group of MP7’s. I believe it was around the 14-15 year models. Engines would have lots of injector codes and not running smoothly. The wiring harness was rubbing the top front of the air compressor. Mack sent out a bulletin it at the time. It’s worth a shot, I remember using a long pry bar to lift up the harness and a mirror to look under it for bare wires , it was hard to reach .

It’s always the yellow and green wires that run between the ECM’s .

If your truck has the metal air cleaner housing that uses the air filter with the metal flange end , the housing has a alignment tab that sometimes gets bent out of the way and the air cleaner housing no longer likes up correctly with the hole in the hood. We would put grease on the rubber sealing gasket on the air cleaner housing and close the hood and then raise the hood to see if the grease transfers the the hood and the hole lines up . Also check in the hood to make sure nothing is blocking the passage ways , there was a bulletin on some of the hoods coming apart inside and clogged the air passages. Also if it has the chrome/metal side hood vents , remove them . Some of the chrome side vents had HP limits on them as they didn’t allow enough air in

Most all the CH/CX style trucks around that time had 3 wires on the chassis harness but usually only 2 wires on the fuel sending unit . The third wire was for a optional style of sending unit that was rarely used. If your dash is the flat panel dash with the old style odometer with the rolling number then the wires from the fuel tank sending unit go pretty much straight to the back of the fuel guage . If you put the two wires together on the sending unit the guage should go to full if the wires are not cut or guage is not bad . If you have the newer rounded dash that started with the CX and then used in the CH trucks and has the digital odometer in the middle upper part of the dash cluster, the fuel sending wires goes to VECU ( vechicle ECM) located in the kick panel in front of the passenger seat. Putting the two wires on the fuel sending unit on this style does nothing to the guage . You will get fault codes with this style if the wiring or sending unit is bad .

You are correct and even the ECM is the same just the software is different. Sometimes we get injectiors in Volvo boxes because the dealer could not get the same injectors in a Mack labeled box. However year model makes a big difference. There are 6 different MP7 injector part numbers and 5 different MP8 injector part numbers depending on year/emissions year model. The same with cylinder head part numbers , 5 for the MP7 and 6 for the MP8’s. The biggest screw ups I remember seeing were putting 2007 emissions year MP8 turbos on 2010/2014 emissions year engines, this caused regen issues. There are at least 3 MP7 turbos and at least 2 MP8 turbo part numbers. Then of course you have the common rail engines which are totally different as well .

The fuel return line above the air compressor swapped with the coolant line to the air compressor? I have seen it happen

On the ASET AC engines the air compressor gets is fresh air from the air filter piping going to the turbo. When the engine is run with a dirty air filter the suction from the turbo is so great tgAt it sucks oil up past the air compressor piston rings and the oil settles in the air filter piping and mouth of the turbo intake . Usually it’s a thick tar like residue. Kinda normal actually. Mack had a couple of bulletins on it but I dont know if it helped any.

All CHU, CXU and GU’s regardless of transmission type have a shrader valve on the air governor that’s mounted to the firewall just for theses situations. Airing it up at this fitting will air up all tanks including the one for the transmission.

Also , all MP engines starting 2010 (DEF fluid ) have two oil pressure sensors, one for the actual oil pressure and one for the piston cooling Oil pressure. On the MP7 they are both on the oil filter stand . On the MP8 the oil pressure sensor is on the driver side of the engine block beside the engine ECM and the piston cooling oil pressure sensor is on the oil filter stand . This leads to lots of confusion on both engines due to the location of which is which. The same sensor part number fits both engines and either location . Plus I believe this same part numbered sensor also is used on the fuel filter stand and the AHI for fuel pressure readings. And years ago we liked to keep no less than 10-15 sensors in the parts room due to high failure rate . A updated sensor came out and has been good for the past couple years.

See if you can find Mack service bulletin FSB 221-010

There were lots of service bulletins on low oil pressure issues on the MP7 engine. We sold very few MP7 trucks when I was at the dealership and the place I work for now only runs MP8 so I never got to personally dive into the issue but it was mostly in hot conditions and under a hard pull or in hills from what I remember

If ETECH. Could be “H ring” in block that holds and alings the roller lifter . It can be dislodged and can cause roller lifter to cam alignment issues