International A26 & MaxxForce Fault Codes Reference | HDT
International HD trucks run two distinct engine families: the current A26 (Detroit DD13 derivative, in production since 2017) and the discontinued MaxxForce 11 / 13 (in production 2010-2017, still in service across many fleets). The codes are different because the engines are fundamentally different. This reference covers both — call out which engine you’re working on before pulling codes. International ServiceMaxx is the OEM platform; aftermarket platforms (JPRO, Jaltest CV, TEXA) cover diagnostic and bidirectional work.
About the two engines
- A26 (2017-current): 12.4L inline-6 built by Daimler (Detroit Diesel) for Navistar / International. Architecturally a derivative of the Detroit DD13. Most A26 fault codes match DD13 codes with minor differences. Strong reliability record. Powers International LT, RH, HX, and HV.
- MaxxForce 11 / 13 (2010-2017): Navistar’s own engine family. 11.0L and 12.4L variants. Built around an EGR-only emissions strategy (no DEF / SCR — used heavy EGR instead). Reliability problems tied to the EGR-only strategy led Navistar to drop MaxxForce in 2017 and adopt the Daimler-built A26 with SCR/DEF.
Diagnostic platforms must be configured for the specific engine. ServiceMaxx connects to either; aftermarket platforms cover both with varying depth.
A26 fuel system codes (Detroit DD13 architecture)
| SPN/FMI | Description | Common cause | Next step |
|---|---|---|---|
| 164/0 | Fuel rail pressure too high | Stuck pressure regulator, failed rail pressure sensor | Live data — commanded vs actual rail pressure. Replace regulator if actual exceeds commanded persistently. |
| 164/1 | Fuel rail pressure too low | Plugged fuel filter, weak feed pump, dropping injector | Filter restriction check, feed pump pressure check, then cylinder cutout via ServiceMaxx if both OK. |
| 651-656/5 | Cylinder N injector circuit fault | Failed injector, harness chafe, ECM driver fault | Run injector solenoid test in ServiceMaxx. |
A26 air handling and aftertreatment codes
| SPN/FMI | Description | Common cause | Next step |
|---|---|---|---|
| 411/4 or 5 | EGR valve position circuit fault | Carbon-coked EGR valve, failed position sensor | EGR valve sweep test. Decarbon or replace if mechanical bind. |
| 2789/14 | VGT actuator commanded position not reached | Carbon on VGT vanes, failed actuator | VGT sweep test. Decarbon or replace turbo for stuck vanes. |
| 3251/0 | DPF differential pressure too high | DPF heavily soot-loaded | Force a stationary regen. If dP doesn’t drop, DPF needs cleaning or replacement. |
| 3361/5 or 7 | DEF dosing valve / injector fault | Crystallized DEF, failed dosing valve | DEF dosing test; inspect dosing line for white DEF crystal buildup. |
| 3936/0 | SCR conversion efficiency low | Failed NOx sensor (most common at 250-400K mi), expired DEF | Compare upstream/downstream NOx data; verify DEF concentration with refractometer. |
| 4334/0 or 1 | DEF pump pressure abnormal | Frozen DEF lines (winter), failed DEF supply pump | Check DEF heater operation in winter; cycle ignition while monitoring pump pressure. |
| 5246/0 or 16 | Aftertreatment derate / inducement | Persistent SCR or DEF fault | Find root SCR/DEF cause first; this is downstream. Inducement reset may require under-load drive cycle. |
MaxxForce 11 / 13 codes (legacy 2010-2017)
| Code | Description | Common cause | Next step |
|---|---|---|---|
| SPN 5298 / FMI 16 | Aftertreatment efficiency low | Heavy EGR-strategy soot buildup, failed sensors | MaxxForce relies on aggressive EGR instead of SCR. The EGR system was the source of most reliability problems. Inspect EGR cooler for cracks (common failure), EGR valve for carbon, and intake manifold for soot buildup. |
| SPN 411 / FMI 7 | EGR valve mechanical fault | EGR valve carbon-coked or stuck | EGR valve cleaning or replacement. MaxxForce EGR valves see significantly more cooled exhaust gas than other platforms; failure is more common. |
| SPN 2630 / FMI 15 | Intake manifold air temp high | EGR cooler crack (very common on MaxxForce) | Inspect EGR cooler for coolant intrusion into intake. Coolant in the intake is a MaxxForce signature failure mode. |
| SPN 3251 / FMI 0 | DPF differential pressure too high | DPF soot loading from EGR-heavy combustion | Force regen. MaxxForce DPFs load faster than SCR-equipped engines. |
| SPN 100 / FMI 1 | Engine oil pressure low | Oil dilution from EGR-strategy fuel issues, mechanical wear | MaxxForce engines often see oil dilution from incomplete combustion. Test oil; mechanical pressure check. |
| SPN 110 / FMI 0 | Coolant temperature high | EGR cooler internal leak, head gasket, water pump | EGR cooler crack is a recurring MaxxForce failure mode. Pressure-test cooling system. |
Engine-specific notes
A26 (current production)
- Built by Daimler / Detroit Diesel for International. Most diagnostic logic mirrors DD13.
- SCR/DEF aftertreatment, standard EGR. Significantly more reliable than MaxxForce predecessor.
- NEXIQ USB-Link 3 is the standard datalink adapter. Pairs with ServiceMaxx and most aftermarket platforms.
- JPRO and Jaltest CV both have strong A26 coverage at diagnostic depth.
MaxxForce 11 / 13 (legacy)
- EGR-only emissions strategy (no DEF / SCR). Created systemic reliability problems that ultimately ended the engine line.
- Common failure modes: EGR cooler cracks, EGR valve carbon buildup, oil dilution, head gasket failures, coolant intrusion into intake.
- Many MaxxForce-equipped trucks have been retrofitted with delete kits or upgraded to A26 power. Plenty are still in service across vocational and regional fleets.
- ServiceMaxx covers MaxxForce. JPRO and Jaltest have decent coverage for fault diagnosis. Reflash requires ServiceMaxx.
Tools we recommend
- International ServiceMaxx — OEM platform for both A26 and MaxxForce. Reflash, parameter programming, full chassis access. Available through Navistar dealer / authorized reseller channels.
- JPRO Professional — strong A26 coverage (DD13 architecture); decent MaxxForce coverage. JPRO packages
- Jaltest CV — multi-brand including International. Solid coverage on both engine families. Jaltest packages
- NEXIQ USB-Link 3 — RP1210 datalink adapter that pairs with all of the above
Frequently asked questions
Stuck on an International code? Free help.
Tell us the engine (A26 or MaxxForce 11/13), the SPN/FMI, what’s been replaced, and what live data you’re seeing. Free phone diagnostic guidance — call (800) 399-9495. Browse multi-brand platforms: JPRO, Jaltest.
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