Diagnostic Health Report – 2012 Freightliner Cascadia (DD13)

Here's the exact diagnostic summary I sent to a client after working on their 2012 Freightliner Cascadia (DD13) on-site. No changes, no tweaks—just the actual email as it is. I share these reports to demonstrate how OnSite Diesel Solutions LLC communicates clearly, diagnoses accurately, and earns trust by being transparent.

OnSite Diesel Solutions, LLC

11631 Oak Ridge Tr.

Marysville, CA 95901

Phone: (916) 224-2880

Tax ID: 33-4021979

Email: ods@onsitedieselsolutions.com

Technician: Manuel/owner

 Summary for Client

Hi [client name],

I performed a pre-health scan on your Freightliner Cascadia and found several active issues. The main concern is the DEF system reporting low pressure, which can prevent proper exhaust treatment and cause performance or emissions issues. This should be addressed quickly.

I also found faults with the coolant level sensor, a few lighting circuits, and an HVAC temperature sensor that may affect cabin temperature control.

We recommend inspecting the DEF dosing system first to ensure its metering properly, followed by electrical checks and a fluid-level verification.

Client: [name]

VIN: 1FUJGEDV8DSBW6663

License Plate: 9E63855

Mileage: 691,610 mi

Engine Hours: 4,680 h

Date: May 28, 2025

Active Fault Codes Summary

Code (SPN/FMI)	Description	Module/ECU	Status	Priority
SPN 111 FMI 19	Coolant Level Sensor: Signal Erratic/Low	DD13 MCM2 (ECM)	Active	Medium
SPN 4334 FMI 7	DEF Pressure Too Low	ACM2 (Aftertreatment)	Active ×5	High
522116 FMI 2	HVAC Air Outlet Temp Sensor: Erratic Reading	SAM CAB	Active	Medium
521906 FMI 5	Left High Beam Headlamp: Open Circuit or Low Current	SAM CAB	Active	Low
520903 FMI 5	Right Tail Lamp: Open Circuit or Low Current	SAM CHASSIS	Active	Low

System Health Overview

• Engine & Cooling System:

  • Coolant level flagged as low 76 times—sensor may be faulty, or coolant level is borderline.

  • Engine overspeed event logged (inactive), no action needed unless recurring.

    
    

• Aftertreatment (DEF/ACM):

  • DEF system reporting low pressure, which may be due to filter blockage, metering valve failure, or pump issue. Pressure reading shows 24.3 psi, but the system expects higher pressure during dosing—high priority.

  • NOx sensor after SCR showed invalid reading, possibly affecting regen readiness.

    
    

• Lighting/Electrical:

  • Left headlight and right taillight show current below normal—likely bulb or wiring-related.

  • Multiple inactive lighting faults logged (brake lights, reverse, turn signals).

    
    

• HVAC System:

  • Air outlet temp sensor reporting erratic values, which may affect cab temp accuracy.

    
    

• ABS, Transmission, Instrument Cluster, Gateway, HVAC, Radio:

• All modules scanned, no active codes stored.

DEF System Snapshot (From Freeze Frame)

• DEF Pressure: 24.3 psi (reading too low during expected metering)

• Metering Rate: 0 g/h

• DPF Inlet Pressure: 0.10 psi

• DOC Temp In/Out: 305.6°F / 334.4°F

• Exhaust Temp After DPF: 478.4°F

• Battery Voltage: 13.56 V

Recommended Repairs & Estimate

Task	Est. Labor (hrs)	Est. Cost (Parts & Labor)	Notes
DEF System Pressure Diagnosis	1.0	$300 – $450	Inspect filter, lines, metering unit
Replace Coolant Level Sensor or Check Level	0.5 – 1.0	$120 – $200	Verify level vs. sensor accuracy
Check/Replace HVAC Temp Sensor	0.5	$100 – $160	Cab temp accuracy fix
Inspect and Repair Headlamp Wiring	0.3	$90 – $140	Restore circuit
Repair Taillamp Circuit	0.3	$90 – $140	May need connector cleaning
Clear Codes and Retest After Repairs	Included	—	Verify fault resolution

Estimated Total (Parts & Labor): $700 – $1,090

Let us know how you'd like to proceed.

Best regards,

Manuel Acosta/owner

OnSite Diesel Solutions, LLC

“OnSite Diesel Solutions LLC – Mobile Diesel Diagnostics & Repair”