manolumber

This is ridiculous, if not a misunderstanding, for a certified Mack dealer. They should be able to hook up to the tractor and read both active (light on) and inactive (light off) trouble codes and get a clue as to what might be happening. Try again, but if you hear the same response, find a new shop.

An update for anyone experiencing the same problem...replaced the DPF outlet/lower pan and absolutely no problems since. I suspect there was a crack at the welded flange of the outlet allowing fresh air to enter and DEF fluid to leak out and solidify at the front clamp. Couldnt see a crack hot or cold but there must have been one as problem solved.

It may help to list the codes exactly as they appear in the drivers information screen or on your scan tool.

Thanks for the replies. As far as I know the updates have been performed but not absolutely sure. I have access to Fleet Impact on the Mack website. Where would I find a description of the available updates so I can check? Would these be "service bulletins"? The insulating blanket is in place at the clamp. The ambient temps have been consistently cold with considerable idle time but as stated we have quite a few of these models and they are used under similar circumstances without this excessive DEF cyrstalization accumulation at the front clamp. I`m suspecting there may be a fresh air leak in the DPF outlet causing the exhaust to cool enough to encourage the DEF to fall out of suspension in the exhaust stream and liquify around the clamp and dribbling out to liquify again when it hits ambient air. Does this make sense or would I be getting NOX codes because there is a leak in the system after the DPF? Thanks again.

Thanks for the replies. Crystalline sublimation (sp?) is a process doable thru tech tool which cleans up crystallization in the SCR. That has been done as a precaution but have other trucks without this pronounced buildup outside the pipe in the clamp area after the DPF. The doser has been changed as a precaution in spite of the original valve checking OK. The new valve was checked for both dribbling/seeping and for volume and checks OK. Once again, no codes indicating anything is wrong with NOX readings and DEF usage volume seems to be normal. We have several of these trucks used under the same circumstances without this problem. Any other ideas? Dealer techs ever encountered this? Thanks

Like the title says...first, the flex pipe between the DPF and the SCR (compact system) was loaded up with solid crystallized DEF, almost restricted. Changed out the DEF injector in spite of the fact its output measured OK via testing with Tech Tool-thought it might be hanging open at times while going down the road. Truck has since been back in shop twice for def crystal buildup at the DPF outlet to flex pipe front clamp. Double checked the DEF injector using DEF system testing in Tech Tool. Injector checks OK. No SCR codes or problems with regen. The temps are OK during a manual regen. Could find no leaks in the exhaust system. Anyone have any ideas? Thanks in advance.

Yes, Celli does still service Macks but I dont know if they sell new ones. Heard M &K has purchased Celli but that info is third hand so take it with a grain of salt.

Thanks...that is exactly where it is, under the front strap. The truck is also a 2013.

Any Mack dealer techs familiar with this weep hole? Thanks

2013 CXU with SCR. Noticed what appeared to be exhaust pulsations leaking out of the SCR under the mounting strap along with a trail of soot while regening. Dealer says this is normal to see from a weep hole which is apparently intended to drain condensate from between the inner and outer shell of the SCR? But with a trail of soot? Thanks in advance for any comments.

Thanks again Porch, great info. So, I can ohm the heater circuits by disconnecting the harness at the module and using the harness pins in that connector because the circuity begins and ends at the module?. Ever any problems with the terminals/connectors at the module? Any idea what the ohm range should be? Obviously if the circuit is open it will be infinity but just curious? I should have mentioned this initially, sorry but I just remembered....when I went to the SCR diagnostics I activated the line heaters manually and showed "100%" reaction on each of the heater circuits. Does this mean the computer is seeing voltage on the return side of the heater circuits? If so, any other reason it would be setting these codes: spn 4354 fmi 5 spn 4356 fmi 5 Thanks again for any advice!

Thanks Porch. Yes, my schematic shows the module and describes the line heater circuits as "outputs" but I was not sure if these outputs are actually voltage out from the module or if there is a fused voltage source which the module grounds. The schematic I have does not show the complete circuit, only the module outputs. Are the line heaters a resistant wrap which extends the length of the line or a heated "block" which is located at specific locations. Everything is thoroughly wrapped so instead of tearing into the whole of the wrapping I was hoping to locate the position of the heaters and connectors and both the source and ground side of the heater ciruits?. Thanks again

Dont know how many hours but from memory I would guess about 200K miles. Is there ever an issue with the line from the dozer valve to the injector? Like an internal flap in the flex section of the line which blocks the line intermittently? Thanks again for sharing your experience!

Have a code for an open circuit on the DEF line heaters. I suspect it may be something simple like a blown fuse or a bad relay. I can find a schematic for the DEF system on the Mack website but it does not include a complete circuit for the line heaters. Checked the legend for the fuse panels and all I can find are main power feeds for the DEF module. I know there are fuses in the left lower fuse panel for the heated side of the NOX sensors. Is there a fuse for the DEF line heaters? Can someone post a complete schematic for the DEF line heaters? The truck in question is a 2012 CXU with catalyzed DPF. Thanks in advance!

Thanks for the reply wheeler. It is a catalyzed system (SCR). A manual regen produces normal temps and the resulting soot reduction but trips the above code. Sounds like I may need the dpf dozer module? Thanks again for the reply