CUMMINS-235 critical Cummins ›

Coolant Level Low - Critical

The CUMMINS-235 (Cummins) diesel fault code means: Coolant Level Low - Critical. This is a critical severity code.

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Keep driving?
No — stop driving
DIY difficulty
intermediate
Estimated cost
$100-$800
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What Are the Symptoms of CUMMINS-235?

  • Engine protect mode or forced shutdown
  • Engine temperature or pressure abnormal
  • Possible engine derate or shutdown
  • Dash warning lamp illuminated
  • Gauges reading outside normal range
  • Audible engine change (knock, ticking, or hiss)

What Causes CUMMINS-235? (Most Likely First)

  • Actual mechanical issue (low oil, coolant, temp) Very Likely
  • Failed sensor falsely reporting Likely
  • Cooling system issue (fan, radiator, pump) Possible
  • Head gasket or combustion gas leak Possible
  • Obstructed airflow at charge air cooler Less Likely

Can I Still Drive with CUMMINS-235?

No — stop driving. CUMMINS-235 is rated critical severity. Continuing to drive in this state risks further damage — get it looked at before your next trip.

Frequently Asked Questions

What is Cummins fault code 235?

Cummins fault code 235 indicates: Coolant Level Low - Critical. It is a critical-severity fault affecting engine mechanical condition.

Can I drive with Cummins fault code 235?

No. Fault code 235 triggers protective engine shutdown or severe derate. Continued operation risks engine damage or stranding. Tow to a Cummins dealer or qualified diesel shop.

How much does it cost to fix Cummins fault 235?

Repair cost is approximately $100-$800 including parts, labor, and any dealer programming required. DIY repairs (sensor replacement) fall at the low end; pump, aftertreatment, or ECM work falls at the high end and usually requires INSITE diagnostic software.

Mechanics Guide Step-by-step diagnosis

How Do You Diagnose CUMMINS-235?

  1. Verify the physical condition indicated by fault 235 -- for temperature codes, confirm with an IR thermometer; for pressure codes, use a mechanical gauge.

  2. Compare mechanical reading to sensor reading on INSITE -- if they disagree, sensor or wiring is faulty.

  3. Inspect the mechanical system (cooling, oil, fuel supply) for the underlying issue reported by the sensor.

  4. Check engine fan operation, coolant level, and radiator condition for temp-related codes.

  5. If mechanical reading confirms the fault, repair the underlying system before clearing codes -- clearing without fix will cause fault return and potential engine damage.

Sources 1

This page is built from documented references. Verify against your own service info before repair work.

  • SAE J1939-73Application Layer: Diagnostics (defines the SPN/FMI fault-identifier framework)

Which Vehicles Commonly Get CUMMINS-235?

  • Peterbilt 579, 567 with Cummins ISX/X15
  • Kenworth T680, T880 with Cummins X15
  • Ram 2500/3500 with 6.7L Cummins
  • Ram 4500/5500 with 6.7L Cummins
  • Freightliner M2 106 with Cummins ISL9/L9

Explore More

More Cummins codes → Diesel home All diesel codes Heavy-duty Guides

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