Injector Cylinder 6 Circuit Current Above Normal / Short
What does VOLVO-MACK-MID128-PID656-FMI6 mean?
The VOLVO-MACK-MID128-PID656-FMI6 (Volvo/Mack D/MP Series) diesel fault code means: Injector Cylinder 6 Circuit Current Above Normal / Short. This is a serious severity code.
Common Symptoms
- Cylinder 6 misfire / rough idle
- White or black smoke at startup
- Power loss and reduced fuel economy
- Engine derate under load
- Check Engine Light illuminated
- Audible clatter or knock from affected bank
Probable Causes (Ranked by Likelihood)
- Failed injector on cylinder 6 (electrical or mechanical) Very Likely
- Harness damage at valve-cover injector connector Likely
- Valve-cover injector pass-through seal leaking oil into connector Likely
- Leaking or stuck injector nozzle (balance failure) Possible
- ECM injector driver output fault Less Likely
Step-by-Step Diagnostic Procedure
Connect Volvo PTT or Mack Guided Diagnostics and run cylinder cutout / balance test; confirm cylinder 6 is the offender.
Measure injector coil resistance at the valve-cover pass-through for cylinder 6 (spec per service manual).
Remove valve cover and inspect injector harness for chafe, oil contamination, or arcing.
Pull the injector and inspect nozzle for clogging, carbon, or cracked tip.
Run injector return-flow balance test — excess return on one cylinder indicates a leaking injector.
After injector replacement, program new injector trim codes via Volvo PTT or Mack Guided Diagnostics.
Frequently Asked Questions
What does Volvo/Mack code MID128-PID656-FMI6 mean?
Volvo/Mack code MID128-PID656-FMI6 (Injector Cylinder 6 Circuit Current Above Normal / Short) 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 MID128-PID656-FMI6?
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 MID128-PID656-FMI6?
Typical repair falls in the range $600-$2,400. 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.