Coolant Temp Below Regulating Temp (Stuck Thermostat)
Can I Drive?
Yes, But Fix Soon
DIY Difficulty
intermediate
Estimated Cost
$200-$600
What does MAXXFORCE-P0128-7 mean?
The MAXXFORCE-P0128-7 (MaxxForce) diesel fault code means: Coolant Temp Below Regulating Temp (Stuck Thermostat). This is a moderate severity code.
Common Symptoms
- Long warm-up
- CEL
- Poor cab heat
Probable Causes (Ranked by Likelihood)
- Stuck open thermostat Very Likely
Step-by-Step Diagnostic Procedure
Replace thermostat.
Frequently Asked Questions
What is P0128 on a MaxxForce 7 (6.4L)?
P0128 on a MaxxForce 7 (6.4L) (2007-2013) indicates: Coolant Temp Below Regulating Temp (Stuck Thermostat). 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 $200-$600 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.