Truck Fault Codes

Detroit DD13 SPN 3480 FMI 5 — DEF Dosing Injector Circuit Open

SPN 3480 FMI 5 on a Detroit DD13 means the ACM2 cannot detect current flow in the DEF dosing injector control circuit. Check the injector wiring harness and connector for damage or corrosion, then measure injector coil resistance. An open reading confirms a failed injector coil. Use Detroit DiagnosticLink to confirm the circuit status and test the injector.

Code Details

Structured details for SPN 3480 FMI 5
Display codeSPN 3480 FMI 5
SPN3480
FMI5
OEM codeNone listed
ManufacturerDetroit Diesel
SystemAftertreatment — DEF dosing system
ComponentDEF dosing injector / wiring circuit
Source addressUnknown or not applicable
Severitymedium
Review statussource backed
Source confidencemedium
Last reviewed2026-06-12

Plain-English Meaning

The DD13 DEF dosing injector sprays precise amounts of DEF into the exhaust upstream of the SCR catalyst. FMI 5 means no current is flowing through the injector circuit — the ACM2 is commanding the injector to activate but getting no response. Without DEF being dosed, the SCR catalyst stops reducing NOx and the inducement sequence will begin. The fault is almost always a broken wire, a corroded connector, or a failed injector solenoid coil.

SPN 3480 is related to Aftertreatment DEF Dosing Unit control in J1939. FMI 5 indicates current below normal or an open circuit in the injector control circuit. On Detroit GHG17 DD13 engines, the ACM2 drives the dosing injector solenoid and monitors for current feedback. A persistent open circuit condition triggers FMI 5. DiagnosticLink can activate the injector and monitor the circuit response to confirm whether the fault is in the wiring, the connector, or the injector coil itself.

Common Symptoms

  • SCR efficiency fault or NOx conversion warning alongside this code
  • DEF dosing quantity showing zero or below commanded levels in DiagnosticLink
  • Possible SCR-related inducement beginning if the fault persists
  • DEF system warning on the instrument cluster

Possible Causes

Possible causes may include the items below. The list is not a parts diagnosis.

  • Broken or chafed wire in the DEF dosing injector harness
  • Corroded or disconnected injector electrical connector
  • Failed DEF dosing injector solenoid coil (open coil resistance)
  • ACM2 output driver fault in rare cases

First Checks

  • Connect Detroit DiagnosticLink and check for companion codes — SPN 4364 (NOx efficiency) alongside 3480 confirms DEF is not reaching the catalyst
  • Inspect the DEF dosing injector harness and connector for physical damage, moisture, or corrosion
  • Measure the injector solenoid coil resistance at the connector with the harness disconnected — an open circuit (infinite ohm reading) confirms a failed coil
  • If coil resistance is within specification, trace the harness back to the ACM2 connector to identify any breaks or high-resistance points
  • Replace the DEF dosing injector if coil resistance confirms an open internal failure

Can I Keep Driving?

Without DEF dosing, the SCR system cannot convert NOx. An SCR efficiency fault will set and the inducement sequence will begin. The truck remains driveable but the fault must be repaired before the inducement derate escalates to a significant power or speed restriction.

SPN 3361 FMI 1Aftertreatment — DEF supply system · DEF supply pump / DEF lines / filter

Related Lookup Pages

Sources

  • Detroit Diesel Service and Diagnostic Resources — Public Reference Detroit Diesel (Daimler Truck North America) · oem · accessed 2026-06-11 · confidence medium

    Source: Detroit Diesel (Daimler Truck North America), Detroit Diesel Service and Diagnostic Resources — Public Reference. 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 DEF dosing injector on the Detroit DD13 the same as on the DD15?

The Detroit GHG17 DD13 and DD15 use similar DEF dosing injector designs as part of the shared aftertreatment architecture. Part numbers may differ by engine configuration or model year. The diagnostic procedure using DiagnosticLink for injector circuit testing is the same for both engines.

Can DEF crystallization block the injector on the DD13?

DEF urea can crystallize at the injector tip when the system is shut down hot and DEF residue dries in the injector orifice. However, SPN 3480 FMI 5 is an electrical fault — an open circuit — not a flow restriction. A crystallized injector tip would produce different fault codes related to dosing quantity rather than a circuit open fault. An electrical measurement at the connector can confirm which type of failure is present.

How does Detroit DiagnosticLink test the DEF dosing injector circuit on the DD13?

DiagnosticLink includes an injector actuation test that commands the ACM2 to activate the dosing injector while monitoring the circuit for current response. If the circuit is open, the test will show no current flowing even when the ACM2 is commanding activation. This test, combined with a resistance measurement at the injector connector, is the primary method to distinguish a wiring fault from an injector coil failure.