Code Details
| Display code | SPN 3480 FMI 5 |
|---|---|
| SPN | 3480 |
| FMI | 5 |
| OEM code | None listed |
| Manufacturer | Mack |
| System | Aftertreatment �?DEF dosing system |
| Component | DEF dosing injector / wiring circuit |
| Source address | Unknown or not applicable |
| Severity | medium |
| Review status | source backed |
| Source confidence | medium |
| Last reviewed | 2026-06-11 |
Plain-English Meaning
The Mack MP8 DEF dosing injector is an electrically actuated valve that delivers precise metered quantities of DEF fluid into the exhaust stream upstream of the SCR catalyst. When the ACM (Aftertreatment Control Module) detects an open circuit on the dosing injector control line, it immediately stops dosing commands because it cannot confirm whether the injector is responding. All DEF delivery stops, the SCR catalyst receives no reductant, and NOx conversion efficiency drops to near zero. On Mack Anthem, Pinnacle, and Granite trucks with the MP8, SPN 3480 FMI 5 triggers an inducement escalation sequence. VCADS Pro (PTT) confirms the fault by showing zero commanded dosing and zero actual dosing in the ACM live data. The most common physical causes are a damaged connector at the injector (corrosion from DEF crystallization around the connector pins) or a failed injector solenoid coil. The Mack MP8 and Volvo D13 share the same dosing injector hardware, so parts availability and diagnostic procedures are identical across both platforms.
SPN 3480 FMI 5 is DEF Dosing Unit circuit open on the Mack MP8 with ACM2.0 aftertreatment. VCADS Pro displays live dosing quantity, commanded dosing cycles, and circuit status for diagnosis.
Common Symptoms
- SPN 5246 FMI 31 alongside this fault
- DEF dosing quantity zero in VCADS Pro
- Inducement warning visible on the Mack instrument cluster
Possible Causes
Possible causes may include the items below. The list is not a parts diagnosis.
- Damaged wire or corroded connector at the dosing injector — DEF crystallization around the connector is a common cause of pin damage
- Failed dosing injector solenoid coil — coil resistance out of specification
- Chafed or broken wire in the dosing injector harness
- Water or DEF ingress into the electrical connector causing a short or open
- ACM output driver fault causing inability to drive the injector circuit
First Checks
- Connect VCADS Pro (PTT) and confirm that the DEF dosing quantity reads zero and the fault is active
- Inspect the DEF dosing injector connector for DEF crystallization, corroded pins, or damaged locking tab
- Measure solenoid coil resistance at the injector connector — typical specification is 0.5–2 ohms; an open reading confirms a failed coil
- Inspect the harness from the ACM to the injector for chafing or damage — run the harness route visually and check for contact with hot surfaces
- If harness and connector are intact and coil resistance is correct, use VCADS Pro to activate the dosing injector — command a dosing cycle and check if the ACM detects a response
Can I Keep Driving?
Driveable; the inducement sequence will escalate to a derate if not repaired.
Related Codes
Related Lookup Pages
Sources
- Mack Trucks Service Support Public Resources Mack Trucks Inc. · oem · accessed 2026-06-11 · confidence medium
Source: Mack Trucks Inc., Mack Trucks Service Support Public Resources. This page paraphrases factual fields only and is not a substitute for the original document.
Open source - Volvo Trucks / Mack Trucks Technical Support Volvo Trucks North America / Mack Trucks Inc. · oem · accessed 2026-06-10 · confidence medium
Source: Volvo Trucks North America / Mack Trucks Inc., Volvo Trucks / Mack Trucks Technical Support. This page paraphrases factual fields only and is not a substitute for the original document.
Open source - SAE J1939 Standards Collection SAE International · official · accessed 2026-05-05 · confidence medium
Source: SAE International, SAE J1939 Standards Collection. This page paraphrases factual fields only and is not a substitute for the original document.
Open source
FAQ
Is the Mack MP8 DEF dosing injector the same part as the Volvo D13?
Yes. The Mack MP8 and Volvo D13 share the same aftertreatment hardware platform, including the DEF dosing injector in most configurations. The same part number typically services both platforms from the same parts inventory. Confirm the correct part number via VCADS Pro (PTT) parts lookup or the Mack/Volvo parts portal using the aftertreatment serial number for the specific model year and aftertreatment tier (EPA 2010, GHG 2017).
How is SPN 3480 FMI 5 different from SPN 3480 FMI 7 on the Mack MP8?
FMI 5 (current below normal / open circuit) indicates an electrical fault �?the solenoid coil is not conducting. FMI 7 (mechanical system not responding) indicates a mechanical fault �?the electrical circuit may be intact but the injector is not producing the expected dosing flow (e.g., stuck valve or blocked orifice). The diagnosis approach differs: FMI 5 is circuit and coil testing; FMI 7 is flow testing and mechanical inspection.
Does replacing the DEF dosing injector on the Mack MP8 require an aftertreatment reset in VCADS Pro?
After injector replacement, VCADS Pro should be used to clear the active fault codes and run the aftertreatment system functional check to confirm the new injector is responding to dosing commands. A complete aftertreatment reset or adaptation procedure may be required depending on the VCADS Pro version and the ACM calibration.