FSB 258-039

Field Service Bulletin
Trucks
Mack Trucks
Greensboro, NC USA
Date
Group
No.
Release
Page
10.2020
258
039
01
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One box SCR fittings, replacement
AN, PI, GR, CHU, CXU
FSB 258-039, SCR Fittings, One Box, Replacement
PM, NOx and Temperature Sensor Fittings
(October 2020)
Certain Mack Trucks AN, PI, GR, CHU, CXU models equipped with aftertreatment system
(One box SCR) may require replacement of SCR fittings such as NOx sensor, temperature
sensor, PM (Particulate Matter) sensor.
Follow the instruction outlined in this FSB to replace the sensor boss or bosses in the one
box SCR. The one box SCR must be removed from vehicle to replace the sensor boss or
bosses. Based on your vehicle configuration, perform any one of the below given standard
repair procedures to remove and install the one box SCR.
Standard Repair Procedure
Labor Code
Muffler, replace. (Combined DOC-DPF-SCR)
2589-03-02-43
OR
Muffler, replace. (Combined DOC-DPF-SCR)
(decontented)
2586-03-02-10
Note: Replacement of aftertreatment muffler is not necessary if the sensor boss threads are
damaged during service.
Mack Trucks released all ATD sensor bosses.
Note: This repair requires TIG or MIG welding and should be performed by a certified
technician. Stainless Steel welding wire/rod (ER308) recommended with appropriate
shielding gas (Argon).
Required Parts
PV729-89480411
Part Description
New part number
Quantity
Boss temperature sensor
23144461
1
Boss NOx sensor
23501651
1
Boss PM sensor
23501654
1
USA152968536
Mack Trucks
Field Service Bulletin
Date
10.2020
Group
No.
Release
258
039
01
Required Tools
Carbide Tip Hole Saw Size
Sensor Boss
1-3/16 (30 mm)
PM Sensor Boss
1-1/4 (32 mm)
NOx Sensor Boss M20
1-1/16 (27 mm)
Temperature Sensor Boss M14
Procedure
WARNING
Risk of burn injuries.
Allow the engine to cool before start work on the Aftermarket system.
CAUTION
Service Information Advisory.
If you are not properly trained and certified in this procedure, ask your supervisor for
training before you perform it.
You must read and understand the precautions and guidelines in Service Information,
Function Group 2, "General Safety Practices, Engine" before performing this procedure.
Note: This repair procedure only applies to the sensor bosses located on the SCR
outlet pipe.
Note: The 1-Box SCR should be removed from the vehicle when the following procedure is
performed.
Note: The illustration shown in this procedure to remove or install the bosses is general,
replace only the damaged boss/bosses. Do not replace the undamaged boss/bosses.
1 Remove the damaged boss welding.
Note: If the PM sensor boss is damaged as shown in the illustration mark the position of
sensor boss notch before removing the boss welding. The notch of PM sensor boss is
always set in the 3’o clock position.
Note: Use the sensor boss to pilot the hole saw.
Note: When removing the sensor boss weld, check the depth frequently to prevent the
damaged sensor boss from falling inside the aftertreatment muffler. Also ensure that the
notch mark is not removed.
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Mack Trucks
Field Service Bulletin
Date
10.2020
Group
No.
Release
258
039
01
T2164806
T5164417
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Mack Trucks
Field Service Bulletin
Date
10.2020
Group
No.
Release
258
039
01
2 Remove the damaged boss/bosses (Temperature/ NOx /PM sensors).
T2164807
3 Clean off all metal shavings from around the sensor boss hole. Prevent metal chips from
entering the Aftertreatment muffler.
4 Verify that the new sensor boss fits the sensor before welding in place.
T2164807
5 Install the new sensor boss and perform the welding.
Note: When replacing the PM sensor boss, position the notch of new boss as marked.
The notch of PM sensor boss is always set in the 3’o clock position.
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Mack Trucks
Field Service Bulletin
Date
10.2020
Group
No.
Release
258
039
01
6 Tack weld the sensor boss, complete the weld around the boss.
T2164806
Reimbursement
This repair may be eligible for reimbursement if a
product failure was experienced within time and
mileage limits of the applicable warranty coverage.
Reimbursement is obtained via the normal claim
handling process.
UCHP
Reimbursement
Claim type (used only when uploading from the
dealer Bus. Sys.)
01
Labor Code
SCR Fittings, one box, replace (one boss)
2589–03–09–04 (0.3 hrs)
Mack Trucks reserves the right to make any changes in design or to make additions to or
upon its products without incurring any obligations to install the same on vehicles previously
built.
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