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.
- Keep driving?
- Yes, but fix soon
- DIY difficulty
- intermediate
- Estimated cost
- $300-$900
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Common Symptoms
- Long warm-up
- Poor cab heat
- CEL
Probable Causes (Ranked by Likelihood)
- Stuck open thermostat Very Likely
Step-by-Step Diagnostic Procedure
Replace thermostat (twin thermostats on 11/13).
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.