Injector Cylinder 6 Circuit Open (J1939)
The VOLVO-MACK-SPN656-FMI5 (Volvo/Mack D/MP Series) diesel fault code means: Injector Cylinder 6 Circuit Open (J1939). This is a serious severity code.
Unverified. We could not confirm this code's definition against freely available manufacturer documentation, so treat the meaning, severity and fix guidance on this page as unconfirmed. Check it against the manufacturer's service information for your exact model and serial range before acting on it. This page is kept out of search engines for that reason, and we are working through this family manual by manual.
- Keep driving?
- Short distances only
- DIY difficulty
- intermediate
- Estimated cost
- $400-$2,500
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View pilot availability →What Are the Symptoms of VOLVO-MACK-SPN656-FMI5?
- Check Engine Light illuminated
- Possible engine derate
- Warning message on driver display
- System-specific warning lamp (DPF/DEF/coolant/etc.)
What Causes VOLVO-MACK-SPN656-FMI5? (Most Likely First)
- Open injector solenoid or cracked coil wire at the valve cover pass-through Very Likely
- Oil contamination at the valve-cover connector (leaking seal) Likely
- ECM injector driver output fault Possible
- Harness chafe damage from valve cover vibration Possible
- Injector internal failure (mechanical stuck) Less Likely
Can I Still Drive with VOLVO-MACK-SPN656-FMI5?
Short distances only. VOLVO-MACK-SPN656-FMI5 is rated serious severity. Keep trips short and get it diagnosed soon rather than waiting for symptoms to worsen.
Frequently Asked Questions
What does Volvo/Mack code SPN656-FMI5 mean?
Volvo/Mack code SPN656-FMI5 (Injector Cylinder 6 Circuit Open (J1939)) is a serious-severity diagnostic trouble code set on D11/MP7, D13/MP8, and D16/MP10 diesel engines in Volvo VNL/VNR and Mack Anthem/Pinnacle/Granite/Titan trucks. It indicates a fault in the fuel injector system and should be read with Volvo Premium Tech Tool (PTT) or Mack Guided Diagnostics.
Can I drive a Volvo or Mack truck with code SPN656-FMI5?
Short distances may be acceptable to reach a repair facility, but the fault will escalate to derate (typically 55 mph then 5 mph on aftertreatment faults). Do not defer diagnosis beyond a shift.
How much does it cost to fix Volvo/Mack code SPN656-FMI5?
Typical repair falls in the range $400-$2,500. Sensor/wiring repairs are at the low end; EGR cooler, NOx sensor set, DEF pump, injector, or head work runs at the high end. Volvo PTT or Mack Guided Diagnostics is normally required for calibration and parameter programming.
Mechanics Guide Step-by-step diagnosis
How Do You Diagnose VOLVO-MACK-SPN656-FMI5?
Connect Volvo PTT or Mack Guided Diagnostics and run injector cutout / balance test for all cylinders.
Measure resistance of the injector coil at the valve cover connector (spec per service manual).
Remove the valve cover and inspect the pass-through connector for oil contamination, cracking, or arcing.
Swap the injector harness between cylinders; if the fault follows the harness, replace the harness.
If harness is clean and coil reads out of spec, replace the injector and program the new trim codes.
After any injector replacement, program injector trim via Volvo PTT or Mack Guided Diagnostics.
Sources 1
This page is built from documented references. Verify against your own service info before repair work.
- SAE J1939-73Application Layer: Diagnostics (defines the SPN/FMI fault-identifier framework)
Which Vehicles Commonly Get VOLVO-MACK-SPN656-FMI5?
- Volvo VNL 760/860 with D13
- Volvo VNR 640 with D11/D13
- Mack Anthem with MP8
- Mack Pinnacle with MP7/MP8
- Mack Granite with MP7/MP8
- Mack Titan with MP10
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