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Category: Medium and Heavy Trucks
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Maxxforce DT with Cylinder Imbalance, 2008 Maxxforce DT with

Customer Question

Maxxforce DT with Cylinder Imbalance
JA: We'll do all we can to help. Tell me a bit more about what's going on so the Heavy Truck Mechanic can help you best.
Customer: 2008 Maxxforce DT with active codes
JA: Is there anything else important you think the Heavy Truck Mechanic should know?
Customer: spn 8006 fmi 0, spn 8002 fmi 0, spn 8001 fmi 1
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Submitted: 3 months ago.
Category: Medium and Heavy Trucks
Customer: replied 3 months ago.
cylinder imbalance test results
cyl1 31, cyl 2 22, cyl 3 22, cyl 4 29, cyl 5 19, cyl 6 23
Expert:  Daniel Wilson replied 3 months ago.

Hi my name is***** will be glad to try to help. What is the complete model of the engine from the Id tag? How many miles on the engine and injectors? Verify your fuel supply pressure is in specs and if okay and not sucking in air you likely have some faulty injectors. It is a good idea to replace the set whenever possible. Let me know

Customer: replied 3 months ago.
Model GDT255
Total engine miles 260,000
Recently replaced injectors 3 & 6, HPOP
Expert:  Daniel Wilson replied 3 months ago.

4561 8001


Cyl Bal

Cylinder balance below minimum limit

4572 8002


Cyl Bal

Cylinder balance maximum limit exceeded

4576 8006


Cyl Bal

Cylinder balance maximum limit


Cylinder Balance Operation

Many factors influence the combustion process in a power cylinder. This can affect the production of torque or horsepower from that cylinder. Some of the factors include piston and cylinder geometry, injector performance, and rail pressure. Variations in these factors can cause unevenness in torque and horsepower from one cylinder to the next. Power cylinder unevenness also causes increased engine noise and vibration, especially at low idle conditions. This is also referred to as rough idle.

The ECM uses a Cylinder Balance control strategy to even the power contribution of the cylinders, particularly at low idle conditions. This strategy incorporates information from the crankshaft position system. The ECM uses the instantaneous engine speed near Top Dead Center (TDC) for each cylinder as an indication of that cylinder's power contribution. The ECM computes a nominal instantaneous engine speed value based on all cylinders. The nominal value would be the expected value from all cylinders if the engine is balanced. By knowing the error quantities, the ECM can add or subtract fuel from a particular cylinder. The control strategy attempts to correct the cylinder unbalance by using fuel quantity compensation through adjustments of the pulse width values for each fuel injector. This method of compensation is repeated until all error quantities are close to zero causing all cylinders to contribute the same amount.

Cylinder Balance Diagnostics



Possible Causes



Cyl (#) balance below min limit

Cyl (#) balance max limit exceeded

  • Electrical fault
  • Low fuel pressure
  • Aerated fuel
  • Contaminated fuel
  • EGR valve stuck open
  • Injection control system
  • Failed injector
  • Base engine compression imbalance

DTC 4561-4566 - Cylinder (#) balance below min limit

DTC 4571-4576 - Cylinder (#) balance max limit exceeded

The ECM continuously calculates the balance of each cylinder during normal engine operation. If a cylinder is under or over performing, a cylinder balance DTC will be set.

Pin-point Cylinder Balance Fault

  1. Visually inspect engine for damaged or disconnected components.

    • Check all fluid levels.
    • Check engine and control system for electrical or mechanical damage.


  2. Check for other active DTCs that could cause a cylinder imbalance.

    • If injector electrical faults are set, diagnose the electrical fault before diagnosing a cylinder imbalance.


  3. Check fuel pressure, fuel aeration, and possible fuel contamination.

    Note: These checks can be verified quickly by using the Fuel Pressure Test Gauge with shut-off valve. See Fuel Pressure and Aeration test in the "Hard Start and No Start" section of this manual.

  4. Check ICP pressure and voltage.

    • Check ICP voltage at KOEO.
    • See "Performance Specifications" appendix in this manual for specification.
    • Check ICP system pressure during KOER. Run KOER Standard Test.
    • See "Performance Specifications" appendix in this manual for specification.


  5. Inspect EGR valve. Verify valve is not stuck open.

    • Run KOEO Standard Test
    • Run KOER Air Management Test.

Repair any faults found in any of the preceding checks before continuing.

  1. Run KOER Injector Disable Test to identify imbalanced cylinder.

  2. Run Relative Compression Test to verify if cylinder imbalance is mechanical issue or injector issue.

    If the Relative Compression Test fails the same cylinder as indicated by Injector Disable Test, the fault is a mechanical failure.

    • Check crankcase pressure.
    • Check valve lash and brake lash (if equipped).
Customer: replied 3 months ago.
steps 1-5 have all previously been completed with results within spec. No fuel aeration or contamination, no electrical faults, injectors tested good. We have not been able to run the air mgt test due to the active codes.
Expert:  Daniel Wilson replied 3 months ago.

Adjust the valves and check compression... also verify the EGR is functioning properly and is not sticking or plugged with soot. Let me know

Customer: replied 3 months ago.
egr was replaced about 6 months ago is clean. Valve lash was set when injectors where replaced about a month ago.
Expert:  Daniel Wilson replied 3 months ago.

Compression test results?

Expert:  Daniel Wilson replied 3 months ago.

If all other possibilities have been eliminated it points to low compression if the others have been confirmed without question.

Customer: replied 3 months ago.
Unfortunately I do not have a compatible compression tester for this engine. The puzzling thing is that the imbalance test results point to cyl 1 & 4 being out most. The most consistent code (Never clears) is cylinder 6 which is in range of the other cylinders. Could that be caused by the ECU or a CCOS? That is what INTL is telling me, and it is an expensive guess.
Expert:  Daniel Wilson replied 3 months ago.

It is possible. Can you get your hands on a test ECM or have yours reflashed and updated to see if it will pass a bench test?

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