HighA26

SPN 4358 FMI 14 International A26 — SCR Efficiency Lo (2026)

SPN 4358 FMI 14 on International A26 means aftertreatment 1 scr catalyst exhaust gas differential pressure - special instructions. 60–80% of field cases trace to plugged scr differential pressure sense lines. Shop repair with parts runs $60 - $3,200; DIY wiring or filter work starts at $40–$150. Diagnosis takes 15–30 minutes with a scan tool and basic electrical checks.

What This Code Means

SPN 4358 FMI 14 on International A26 tells the ECM that scr catalyst exhaust differential pressure is outside calibrated limits. On J1939, FMI 14 specifies the failure mode: Aftertreatment 1 SCR Catalyst Exhaust Gas Differential Pressure - Special Instructions. The trip counter usually requires 2–5 seconds of continuous fault before storing active status. SCR differential pressure tells the International ECM whether exhaust flow through the catalyst is normal. FMI 14 means the diagnosis is not complete until you follow the OEM procedure for line inspection, sensor cross-check, and restriction verification. ProfessionalDieselRepair.com treats plugged sense tubes as the default cause until manometer data proves otherwise.

Common Symptoms

• Aftertreatment warning lamp with SPN 4358 FMI 14 (100% of cases)
• SCR differential pressure reading stuck or implausible on ServiceMaxx (80% of cases)
• Gradual power loss if restriction is genuine (60% of cases)
• Possible companion DPF or DOC pressure codes (40% of cases)
• Inducement countdown on some calibrations if unresolved (25% of cases)

Likely Causes (Ranked by Probability)

1. Plugged SCR differential pressure sense lines (45% of cases) — Soot and condensation block narrow sample tubes, producing false high differential pressure readings.

2. Failed SCR differential pressure sensor (25% of cases) — Sensor drift or internal diaphragm damage reports incorrect pressure after sense lines test clean.

3. Ash or soot loading restricting SCR substrate (15% of cases) — Genuine catalyst restriction raises differential pressure under load when sense lines are clear.

4. Damaged catalyst from prior thermal event (10% of cases) — Melted or collapsed substrate creates permanent high backpressure confirmed by direct measurement.

Step-by-Step Diagnostic Guide

1. Connect ServiceMaxx or Noregon JPRO and open SPN 4358 special instruction workflow for International aftertreatment. — Tool: scan tool or multimeter. Document readings on the work order.

2. Inspect SCR differential pressure sense lines at both catalyst ports for soot, kinks, or moisture plugs. — Tool: scan tool or multimeter. Document readings on the work order.

3. Compare scan tool differential pressure to a manual manometer tee’d into sense ports. — Tool: scan tool or multimeter. Document readings on the work order.

4. Run idle and loaded pressure profiles — flat high reading with clear lines suggests sensor fault; rising pressure with load suggests restriction. — Tool: scan tool or multimeter. Document readings on the work order.

5. Clear sense lines or replace sensor per special instructions before authorizing SCR catalyst replacement. — Tool: scan tool or multimeter. Document readings on the work order.

Repair Options (with Costs)

Repair	DIY	Independent Shop	Dealer
SCR Catalyst Exhaust Differential Pressure wiring repair	$25–$150	$150–$350	$250–$500
SCR Catalyst Exhaust Differential Pressure sensor/part	$60 - $3,200	$$60 - $3,200 + labor	$850+
Full module replacement	N/A	$600–$1,500	$850+

Platform-Specific Notes

On International A26, this code follows OEM J1939 diagnostic logic. Verify thresholds and pinouts against service information for your engine serial — calibrations differ between model years even within the same platform.

When This Code Sets

SPN 4358 FMI 14 sets when scr catalyst exhaust differential pressure fails the J1939 rationality monitor for a calibrated trip counter — usually 2–5 seconds continuous on electrical faults, longer on efficiency monitors. Freeze-frame on International captures RPM, torque, exhaust temperature, and DEF level at fault set.

Scan Tool Parameters to Log

• Inlet vs outlet NOx (ppm)
• SCR efficiency %
• DEF level and quality/concentration
• DEF tank temperature

Common Misdiagnoses

Ordering SCR catalyst before sense line inspection — High differential pressure sounds like a restricted brick.. Instead: Follow FMI 14 special instructions — clear tubes and manometer-test first; a parts-cannon catalyst on a plugged hose is an expensive misdiagnosis.

Replacing sensor without confirming actual exhaust delta-P — Sensor is named in SPN 4358.. Instead: Tee a manometer into sense ports — if mechanical reading is normal, fix wiring or ECM; if high, investigate restriction.

Ignoring companion DPF codes — SCR and DPF faults are treated as separate systems.. Instead: Upstream DPF restriction can elevate SCR differential pressure — diagnose exhaust path holistically.

Shop Notes from the Field

ProfessionalDieselRepair.com clears SCR sense tubes before any catalyst quote on International SPN 4358 FMI 14. FMI 14 includes manometer cross-check steps — a plugged sample line and a melted brick look identical on the dash, and only one of them needs a five-figure aftertreatment module. Skipping the procedure is parts-cannon at fleet scale.

Safety Warning

• Allow SCR housing to cool before disconnecting pressure sense fittings.
• Wear heat-resistant gloves when working under the aftertreatment module.
• Relieve residual pressure in sense lines slowly when disconnecting.

Prevention Tips

• Blow out SCR sense lines during scheduled aftertreatment PM.
• Use approved DEF to limit ash accumulation in the catalyst.
• Address DPF restriction before SCR pressure climbs.
• Keep manometer test ports capped and free of debris after service.

International Field Notes for SPN 4358 FMI 14

• Torque scr catalyst exhaust differential pressure mounting fasteners per International OEM spec — verify with engine serial. After repair, road test 25 miles under load logging live data to confirm fix.
• Document ambient temperature and key-cycle count at fault set on International A26 — cold-soak faults on scr catalyst exhaust differential pressure often clear after warm-up when moisture is the root cause.
• Compare this unit’s repair history: repeat SPN 4358 FMI 14 within 5,000 miles indicates incomplete prior repair, not a new component failure.
• If scr catalyst exhaust differential pressure was recently replaced, verify correct part number for engine serial — superseded calibrations require matching hardware revision on International.
• Capture a 20-minute data log of scr catalyst exhaust differential pressure parameter during mixed driving before closing the work order — intermittent FMI signatures need road replication, not bay-idle checks.
• Check for OEM technical service bulletins covering SPN 4358 FMI 14 on A26 — many bulletin fixes address harness routing rather than sensor replacement.
• Torque scr catalyst exhaust differential pressure mounting fasteners per International OEM spec — verify with engine serial. After repair, road test 25 miles under load logging live data to confirm fix.
• Document ambient temperature and key-cycle count at fault set on International A26 — cold-soak faults on scr catalyst exhaust differential pressure often clear after warm-up when moisture is the root cause.
• Compare this unit’s repair history: repeat SPN 4358 FMI 14 within 5,000 miles indicates incomplete prior repair, not a new component failure.
• If scr catalyst exhaust differential pressure was recently replaced, verify correct part number for engine serial — superseded calibrations require matching hardware revision on International.
• Capture a 20-minute data log of scr catalyst exhaust differential pressure parameter during mixed driving before closing the work order — intermittent FMI signatures need road replication, not bay-idle checks.
• Check for OEM technical service bulletins covering SPN 4358 FMI 14 on A26 — many bulletin fixes address harness routing rather than sensor replacement.

Related Codes

• SPN 3251 FMI 14 — often stacks with SPN 4358 FMI 14
• SPN 4360 FMI 14 — often stacks with SPN 4358 FMI 14
• SPN 5246 FMI 7 — often stacks with SPN 4358 FMI 14

FAQ

What does International SPN 4358 FMI 14 mean?

SCR catalyst differential pressure fault requiring OEM special instruction diagnosis beyond generic FMI definitions.

Can plugged sense lines cause this code?

Yes — blocked sample tubes are the most common root cause on International aftertreatment.

Which tools diagnose SPN 4358 FMI 14?

ServiceMaxx, Noregon JPRO, and Jaltest all read SCR differential pressure and special instruction text.

What does SPN 4358 FMI 14 mean on International A26?

SPN 4358 FMI 14 means aftertreatment 1 scr catalyst exhaust gas differential pressure - special instructions. The ECM detected scr catalyst exhaust differential pressure outside calibrated limits. Verify with freeze-frame data before clearing.

Can I drive with SPN 4358 FMI 14 active?

Short distances only if power is normal. Derate or shutdown can follow within one drive cycle — diagnose before the next loaded haul.

How much does it cost to fix SPN 4358 FMI 14?

DIY repairs start at $40–$150 for wiring or filters. Shop repairs with parts run $60 - $3,200. Dealer pricing runs $850+.

What is the most common cause of SPN 4358 FMI 14?

Plugged SCR differential pressure sense lines — confirm with visual inspection and live data before ordering parts.

Sources

• SAE J1939-71 — SPN 4358 parameter definition
• International OEM service information — verify by engine serial
• Mitchell1 ProDemand — 2026 labor and parts cost surveys

Related Reading

• International fault codes hub
• Diesel repair cost estimator
• SCR Catalyst Exhaust Differential Pressure diagnostic guide
• SPN 3251 FMI 14
• SPN 4360 FMI 14