Check engine light

No, let them do there job and tell you the issue. They are the pros.
Do you go to the doctors and tell the doctor what is wrong with you? Just a comparison.

Tell him the same story you told us and let them go with it and come back with there findings.

A loose material in a cat will not code.

Roy

Cycle ignition key ON OFF ON OFF ON read P0000 codes in the odometer area
let me know what you have for codes
this way we can tell what emission hose you need

DTC P0455: EVAP LEAK MONITOR LARGE LEAK DETECTED & DTC P0456: EVAP LEAK MONITOR SMALL LEAK DETECTED

NOTE: All Evaporative Emissions (EVAP) leak monitor DTCs listed above are diagnosed using the same test.

NOTE: If Powertrain Control Module (PCM) is replaced, PCM must be reprogrammed. See POWERTRAIN CONTROL MODULE under PROGRAMMING. After each repair procedure has been completed, reconnect all components and perform POWERTRAIN VERIFICATION TEST VER-6 under VERIFICATION TESTS to ensure system is functioning
properly.

Possible Causes
? Intermittent Condition
? EVAP Leak Detection
? EVAP Purge Solenoid Leaks/Stuck Open
? Intermittent Leak Detection Pump (LDP) Monitor Failure
? PCM

NOTE: A loose gas cap could have caused this DTC to set. Ensure gas cap is tight, in good condition and meets original equipment manufacturer's specifications.

Testing
1. Turn the ignition on, with the engine off. With the DRBIII(R), read DTCs. Is the Good Trip Counter displayed and equal to zero? If yes, go to next step. If no, go to step 5.
WARNING: Keep lighted cigarettes, sparks, flames, and other ignition sources away from the test area to prevent the ignition of explosive gases. Keep the test area well ventilated.
NOTE: The fuel tank should have 20-80 percent of fuel tank capacity to properly test the EVAP system. To continue testing, you will need Miller EVAP Emission Leak Detector (EELD) tool (8404).

2. Disconnect the vacuum supply hose at the LDP. Connect and apply a continuous vacuum supply of about 20 in. Hg to the LDP. A vacuum pump such as an A/C recovery unit works well. Using the DRBIII(R), select Engine, System Tests and actuate the LDP Test (Option 3/Hold PSI). This energizes the LDP solenoid and allows the constant vacuum source to apply vacuum to the LDP pump diaphragm. This lifts the diaphragm up and seals the atmospheric canister vent valve at the bottom of the LDP. Connect the Red power lead of the EELD to the battery positive terminal and the Black ground lead to battery negative terminal. Connect shop air to the EELD. Set the Smoke/Air control switch to Air. Insert the EELD air supply tip (Clear hose) into the appropriate calibration orifice on the EELD control panel (based on DTC leak size). Press the remote Smoke/Air Start button. Position the Red flag on the air flow meter so it is aligned with the indicator ball. When the calibration is complete, release the remote button. The EELD has now calibrated the flow meter in liters per minute to the size leak indicated by the DTC set in the PCM. Install the Service Port Adapter (8404-14) on the vehicle's service port. Connect the Air supply hose from the EELD to the service port. Press the remote button to activate air flow. Larger volume fuel tanks, and/or those with less fuel, may require 4-5 minutes to fill. Compare the flow meter indicator ball reading to the Red flag. Above the Red flag indicates a leak present. Below the Red flag indicates a sealed system. Is the indicator ball above the Red flag? If yes, go to next step. If no, go to step 5.
NOTE: A thorough visual inspection of the EVAP system hoses, tubes, and connections may save time in your diagnosis. Look for any physical damage or signs of wetness at connections. The strong smell of fuel vapors may aid diagnosis also. To continue testing, you will need the EELD.

3. Remove the air supply hose from the service port. Connect the smoke supply tip (Black hose) to the service port. Set the Smoke/Air control switch to Smoke. The flow meter indicator ball will not move at this point. Press the remote Smoke/Air Start button. Ensure that smoke has filled the EVAP system by continuing to press the remote Smoke/Air Start button, remove the vehicle fuel cap, and wait for the smoke to exit. Once smoke is indicated, reinstall the fuel cap. For optimal performance, introduce smoke into the system for an additional 60 seconds, continue introducing smoke at 15 second intervals, as necessary. While still holding the remote Smoke/Air Start button, use the White Light (8404-CLL) to follow the EVAP system path, and look for the source of the leak indicated by exiting smoke. If a leak is concealed from view such as on top of fuel tank, release the remote Smoke/Air Start button, and use the Ultraviolet Black Light (8404-UVL) and the Yellow Goggles (8404-20) to look for residual traces of dye left behind by the smoke. The exiting smoke deposits a residual fluid that is either Bright Green or Bright Yellow when viewed with UVL. Was a leak found? If yes, repair or replace the leaking component as necessary. If no, go to next step.
NOTE: After disconnecting the EVAP purge solenoid vacuum connections, inspect the lines and solenoid for any signs of contamination from the EVAP canister. This may indicate a faulty rollover valve. Replace/repair as necessary.

4. Turn the ignition off. Disconnect the vacuum hoses at the EVAP purge solenoid. Using a hand vacuum pump, apply 10 in. Hg of vacuum to the EVAP purge solenoid vacuum source port (component side). Monitor the vacuum gauge for at least 15 seconds. Does the EVAP purge solenoid hold vacuum? If yes, go next step. If no, replace the EVAP purge solenoid.
NOTE: Use the Freeze Frame Data to help duplicate the conditions that set the DTC. Pay particular attention to the DTC set conditions, such as, VSS, MAP, ECT, and Load. A thorough visual inspection of the EVAP system hoses, tubes and connections may save time in your diagnosis. Look for any physical damage or signs of wetness at connections. The strong smell of fuel vapors may aid diagnosis also.

5. Conditions that set DTC are not present at this time. Refer to any Technical Service Bulletin (TSB) that may apply. With the DRBIII(R) in System Tests, perform the LDP Monitor Test. This will force the PCM to run the LDP Monitor. If the monitor fails, further diagnosis is required to find faulty component. If the monitor passes, the condition is not present at this time. Were any problems found? If yes, repair as necessary. If no, test is complete.

For leaks in the evaporative emission system, it depends on the code. For big leaks, look for hoses disconnected, loose gas cap, etc. For small leaks you really need a smoke machine. That allows you to inject white non-toxic smoke at 2 psi, then you search for where it's sneaking out.

There are a lot of oxygen sensor codes. The course of action depends on which code and for which sensor.

P0141 †Oxygen Sensor Heater Circuit Malfunction (Bank 1 Sensor 2)

That would be the driver's side, downstream sensor, (after the mini catalytic converter). If this truck does not have the California emissions package, it will only have two O2 sensors, not 4.