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A26 Engine Fault

International Commercial Truck

Severity: Moderate

Source: OnlyErrorCodes.com — Every error code. One place.

International A26 Engine Fault — Causes & Fixes

What it means

An International amber engine warning indicates an A26 or S13 engine fault stored in the ECM.
A J1939 scan tool reads SPN and FMI codes.
Navistar's diagnostic tool (Diamond Logic Builder, ServiceMaxx) is needed for detailed work.

Affected Models

  • International LT
  • International RH
  • International HV
  • International HX
  • International MV
  • International CV

Common Causes

  • A26 / S13 engine sensor fault (boost, EGR, NOx, etc.)
  • EGR valve carbon buildup or actuator failure
  • Variable geometry turbocharger (VGT) actuator fault
  • DPF or DOC differential pressure sensor failure
  • NOx sensor inlet or outlet failure

How to Fix It

  1. Check warning urgency.

    Amber check engine = stored fault, usually drivable.
    Red stop engine or rapid-flash amber = serious — pull over safely as soon as practical.

  2. Read codes with a J1939 scanner.

    Connect a heavy-duty scanner (such as JPRO, Noregon DLA, or Texa) to the J1939 connector under the dash.
    The SPN identifies the component and FMI identifies the fault type.

  3. Inspect basic items.

    Verify oil, coolant, and DEF levels.
    Look for visible leaks, disconnected hoses, and damaged sensors.
    Many fault codes have simple physical causes.

  4. Take to a Navistar-authorised shop.

    ServiceMaxx is required for many advanced functions — actuator tests, EGR resets, parameter changes.
    An International dealer or Navistar-trained shop can perform full diagnostics and proper repairs.

When to Call a Professional

International dealers and Navistar-authorised shops use ServiceMaxx and Diamond Logic Builder for full diagnostics.
For complex faults, especially after-treatment-related, professional service is the most efficient route.

Frequently Asked Questions

What is the International A26 engine?

The A26 is Navistar's 12.4-liter inline-six diesel engine introduced in 2017 for Class 8 trucks. It replaced the older N13 in many International LT and HX models. The newer S13 (introduced 2023) extends the platform with improved emissions and fuel economy.

Can I clear an International engine fault by disconnecting the battery?

No. Heavy-duty engine ECMs retain fault codes through battery disconnects. Codes can only be cleared with a scan tool after the underlying issue is resolved.