Mackpro

Just wanted to say that the Rislone Crystal Clear DEF cleaner is a good last resort to try before condemning and replace the SCR box on 2010-2016 Mack’s and Volvo’s. It did work on a truck I was helping on that had 1,009,010 miles on a mostly original engine and aftertreatment system. Tested and updated and replaced all the usual parts but still had P20EE code returning after a day or two. Put 2 bottles in it actually worked.

Also, does the bad ECM’s smell burned? I’ve had several that you could smell it as soon as you unplugged the connectors. Some had melted pins even. Also look and see if there is a bracket that’s is bolted to the air compressor head that holds the chassis harness before it plugs into the engine harness at the big green connector. Seen the power wire for engine ecm rub and short out on this bracket. Usually it blows the engine ECm fuse but not always.

Carefully check the ground stud that’s welded to the frame behind the battery box. We have seen issues there with broken eyelet/ring terminal ends on the ground wires. If your battery box is on the driver side we have seen people remove transmissions and not put the battery cable brackets back on the transmission and found the positive cable shorting on the frame and various other places causing engine to cut out and /or die. Check and tighten the power and ground cables on the cab pass through by the wiper motor on the fire wall. Do the same on the inside above the accelerator pedal. You have to pull down the duct work with a T27 screwdriver to get it it. There is an unused open ended connector for heated seats by the inside pass through positive cable stud , I’ve seen the negative wire in this connector touch the positive stud and cause crazy problems. I think I might trust a TEMU or eBay ECM over a used Mack /Volvo one. The rubber insulation washers on the ECM shrink after a couple of years and the ECM just sits there and shakes its self to death. A used ECM could be on its last run as any given moment. If the truck was idling up to 1000 on its own then there was definitely a low voltage issue causing this. Usually when everything is perfect and new batteries and new alternator the voltage on the display is 13.6 or 13.7.

If it cranks for exactly 3 seconds and then quits cranking like you let the key up. Thats a sign of crank shaft and camshaft sensors mismatch readings. Surprisingly it won’t set a fault code for this.

Power to Pin 85 comes from the VECU Vehicle control unit . The key switch in the start position sends 12 volts to pin A6 of the VECU, then if everything looks good to the VECU it sends 12 volts out pin B28 to the start relay pin 85

Also relay 36 has to be installed correctly or it won’t start.

Check voltage on both side of fuse 7 with the key on. Dont use a test light. Use an actual meter. The wire coming out of fuse 7 is labeled F7A1. It actually goes out the firewall in the big 100+ pin pass through. It’s pin 68 . Then comes back into the fuse box on the top connector bottom pin

Pin 30 should have 12 volts with key on . This is looking into the fuse box with relay out

I believe you can still get the original paper engine overhaul manual and engine electric troubleshooting manual for the 2004 emission year MP7 that’s in the CTP/CXP. I still have my copies . A lot of the stuff has gone to digital download on E-media.

Have the injectors been changed recently? If so, possibly the incorrect ones were installed. Only the first few years of the ETECH style engines had the injector fuel return system in the cylinder heads that went to the fuel pressure regulator via plastic push on fuel return hose. Here in the US the year model range was about 1998.5 to 2001.5 . Then the CCRS and ASET family of engines came out and all used the “leakless” injectors which did not have the plastic fuel return line coming off the cylinder head. A lot of the newer cylinder head casting still had the passage ways in the heads for fuel return system but had pipe plugs in them to block them off. Also the ETECHs with the fuel return in the cylinder heads need 2 O-rings on each injector. The “ leakless “ injectors only need the top O-ring.

The * is for some kind of “ Limp Home” mode if you have certain transmission fault codes. I’ve never seen it used.

The fleet shift pad can be replaced with the performance shifter but a software update has to be done by the dealership. The dealership has to request a software change from corporate. After the software is turned on and installed in the truck, there is a parameter in the settings that needs to be changed as well. There are 3 options for this parameter. One is performance mode turned off , one is performance mode on but will return to economy mode after truck reaches a drop in engine load ( up to cruising speed), the last is performance mode on and will stay on till you turn it off on the shift pad or cycle the key switch. On your fleet shift pad if you hit the “M” manual mode button all this does is hold you in the gear you are in.