Coolant Below Thermostat Regulating Temp
The MAXXFORCE-P0128-11 (MaxxForce) diesel fault code means: Coolant Below Thermostat Regulating Temp. This is a moderate 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?
- Yes, but fix soon
- DIY difficulty
- intermediate
- Estimated cost
- $300-$900
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View pilot availability →What Are the Symptoms of MAXXFORCE-P0128-11?
- Long warm-up
- Poor cab heat
- CEL
What Causes MAXXFORCE-P0128-11? (Most Likely First)
- Stuck open thermostat Very Likely
Can I Still Drive with MAXXFORCE-P0128-11?
Yes, but fix soon. MAXXFORCE-P0128-11 is rated moderate severity. It is not an immediate stop-driving fault, but it will not clear itself — book the repair rather than ignoring it.
Frequently Asked Questions
What is P0128 on a MaxxForce 11 (10.5L)?
P0128 on a MaxxForce 11 (10.5L) (2008-2014) indicates: Coolant Below Thermostat Regulating Temp. This is a known fault code on the MaxxForce engine family and typically points to the causes listed above.
Can I drive with P0128 on my MaxxForce?
Yes, you can generally drive with this code, but diagnose soon to prevent secondary damage.
How much does it cost to fix MaxxForce P0128?
Repair cost is typically $300-$900 depending on the underlying cause and shop rate. Many MaxxForce faults (especially EGR cooler, head bolt, and VGT repairs) are major expenses that drove fleet owners to repower with Cummins or retire these trucks early.
Mechanics Guide Step-by-step diagnosis
How Do You Diagnose MAXXFORCE-P0128-11?
Replace thermostat (twin thermostats on 11/13).
Which Vehicles Commonly Get MAXXFORCE-P0128-11?
- International ProStar MaxxForce 11
- International TranStar 8600 MaxxForce 11
- International PayStar 5900 MaxxForce 11
- International WorkStar 7600 MaxxForce 11
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