TSB110181-012720

2/3/2020
Engine Speed Instability Related to Truck Vacuum Blower or Pump Engagement
Technical Service Bulletin
Technical Service Bulletin: TSB110181
Released Date: 27-Jan-2020
Engine Speed Instability Related to Truck Vacuum Blower or Pump Engagement
Engine Speed Instability Related to Truck Vacuum
Blower or Pump Engagement
Core Issue
Some units, with transfer cases, have exhibited low power and/or engine speed instability when
the transfer case or pump system is engaged. This instability typically causes the operator to shut
down the system. New engine control module (ECM) software has added new engine speed
governor tuning that can address most of these issues. Other possible causes include incorrect
setting of ECM Features and Parameters.
Confirmation
Product Affected:
ISL9 CM2350 L101
L9 CM2350 L116B
L9N CM2380 L124B
ISX15 CM2250
ISX15 CM2250 SN
ISX15 CM2350 X101
ISX12 CM2350 X102
ISX12/ISX11.9 CM2250
X12 CM2350 X119B
ISX12N CM2380 X120B
In order to properly test for low power or instability; the unit must be operated with the
transmission in gear, the transfer case engaged, and a load placed on the engine.
1. If the unit displays vehicle speed on the dash during operation, most likely the Transmission
Driven PTO feature is not properly set up. Reference “Resolution” section for proper feature
settings.
2. Incorrect Transmission Driven PTO Type may have been selected. Reference “Resolution”
below for proper feature settings.
3. The truck body builder may have disabled the vehicle speed sensor (VSS) signal to the ECM.
4. The truck original equipment manufacturer (OEM) may have installed an additional PTO
switch that may be labeled “PTO Control”. This switch will disable the VSS signal to the ECM.
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Engine Speed Instability Related to Truck Vacuum Blower or Pump Engagement
5. Check for engine control module (ECM) updates for this issue on QuickServe™ Online or
using latest INCAL™ DVD.
6. Check for fault codes, including intermittent ones.
7. If the vehicle has a Parking Brake Switch input that is either wired directly to the ECM or is
multiplexed within, INSITE™ electronic service tool Parking Brake Switch must be ENABLED.
Note : If the vehicle does not have a parking brake switch input, then the OEM or body
builder must install the governor type switch to indicate to the ECM when the transfer
case is engaged.
Resolution
1. Proper settings for Transmission Driven PTO:
PTO - Alternate Operation - Enable (Recommended for fire trucks and vacuum trucks
only)
Recommended to disable feature for all other applications.
PTO - Ignore Vehicle Speed Source in PTO - Disable
PTO - Transmission Driven PTO - Enable
Vacuum Trucks Only - PTO - Transmission Driven PTO - Transmission Driven PTO
Type - Transmission Driven - Irregular Load.
Well Drilling Rigs Only – PTO – Transmission Driven PTO – Transmission Driven PTO
Type – Transmission Driven – Steady Load.
Concrete Pumping Trucks Only – PTO – Transmission Driven PTO – Transmission
Driven PTO Type – Transmission Driven – Cyclic Load.
All Other Rigs – Choose the setting that provides the best PTO performance.
2. Proper settings for PTO:
PTO - Maximum Engine Load - Backward calculate, using the manufacturer’s torque
rating for the PTO device and the gear ratio between the device and the engine.
Maximum Engine Load = Rated Torque/Gear Ratio.
3. Restore the VSS signal back to original factory condition. Ensure the VSS circuit is not
interrupted. The ECM must read vehicle speed for the feature to work.
4. Check for engine control module (ECM) updates for this issue on QuickServe™ Online or
using latest INCAL™ DVD. Update the ECM calibration. Reference Procedure 019-032. See
Service Manual.
5. Repair all fault codes.
If none of the above resolves the issue, contact your authorized Cummins® repair location. For
authorized Cummins® repair locations, follow your technical support escalation process.
Warranty Statement
The information in this document has no effect on present warranty coverage or repair practices,
nor does it authorize TRP or Campaign actions.
Document History
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Engine Speed Instability Related to Truck Vacuum Blower or Pump Engagement
Date
Details
2011-6-14
Module Created
2011-12-21
Updated Information.
2012-2-27
Updated Information.
2014-9-29
Additional engines added.
2015-4-22
Additional engines added.
2016-3-14
Added statement about transfer cases, note about parking brake
switch input, and recommendation for fire trucks and vacuum trucks
only. Changed reference about placing a load on the engine vacuum
system to placing a load on just the engine.
2019-5-24
Added X12 CM2350 X119B
2020-1-23
Additional engines added.
Last Modified: 27-Jan-2020
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