It is difficult to provide any advise when you dont have a code to work from. You can get the fault code without a scan tool but for about what you paid the shop you can get a ScanGuage D which plugs into the diagnostic port and will give you fault codes (along with live data readings, like engine boost, temperatures, etc.).
https://shop.advanceautoparts.com/p/scangauge-d-digital-trip-monitor-sgd/10382992-p?c3ch=PLA&c3nid=10382992-P&adtype=pla_with_promotion&gclid=CjwKCAjwvuzkBRAhEiwA9E3FUuGJZ_reFOyLIrfA5_kaVy0x8kZieijm-qlO-WrrmJ7DcE3HdFwpnhoCrecQAvD_BwE&gclsrc=aw.dsHow to retrieve fault codes without a scan tool___
From the owners manual:Engine Diagnostics:
The engine diagnostics will notify the operator of any deviations from the programmed limits of
the engine through the "Check Engine" lamp in the dashboard. Should a system component with the
engine develop a deviation, the "Check Engine" lamp will illuminate, and a diagnostic code will be
logged and stored in the system memory. These codes may be accessed using either a service tool or
by using the cruise control switches to read the diagnostic flash code.
To access the diagnostic flash code using the cruise control switches, perform the following
actions (service only):
1. Turn the
ignition switch to the ON position.
2. Turn the
cruise control power switch to the OFF position.
3.
Engage and hold either the cruise control "Set" or "Resume" switch until the Check Engine
lamp illuminates and begins to flash.4. The lamp will flash a number of times followed by a pause and a second series of flashes.
Count
the number of flashes to determine the two digit flash code. EXAMPLE: The lamp flashes four times
followed by a two second pause, and then one more flash indicating a flash code of 41-Vehicle
Overspeed Warning.
5. A code of 55 indicates no faults found. After noting any flash codes present, refer to the
Engine Diagnostics section of the Caterpillar Operation & Maintenance Manual for code description
and necessary action.
