Diesel Trouble Codes

FC 2346 — Turbocharger Turbine Intake Temperature – Above Normal (SPN 2789 FMI 15) — Cummins ISX15

Diagnostic reference for Cummins ISX15 (2010–2017) FC 2346.

Updated October 15, 2026

What it means

FC 2346 is SPN 2789 FMI 15. Generic definition: exhaust temperature at the turbine inlet exceeded its limit. Typical on this platform: excess fueling, boost or air restriction problems, or EGR faults.1

Most likely causes

  1. Excess fueling from injector or fuel system faults raising turbine inlet temperature. — High fuel delivery increases exhaust heat entering the turbo. On ISX15, excess fueling is a typical contributor to SPN 2789 FMI 15.1
  2. Boost or intake air restriction causing higher exhaust temperatures. — Restricted intake or boost leaks alter combustion and can raise turbine inlet temperature. Boost/air restriction problems are listed as typical for this code on this platform.1
  3. EGR system faults affecting combustion temperature. — EGR faults are noted as typical for SPN 2789 FMI 15 on the ISX15.1

How to diagnose

  1. Verify active codes and freeze-frame data for load, rpm, and intake conditions at setpoint.
  2. Inspect intake system for restrictions and check boost pressure vs expected values.
  3. Review fuel system data for rail pressure control and injector performance; look for companion fuel-related codes.
  4. Check EGR system data including EGR valve position, cooler temperature, and differential pressure; inspect for restrictions or cooler issues.
  5. Inspect turbocharger VGT actuator operation and vane freedom; check for boost leaks and exhaust restrictions downstream of the turbine.
  6. Compare turbine inlet temperature sensor readings to related exhaust temperature sensors and verify sensor plausibility.
  7. If other temperature-related codes are present (e.g., DPF intake temperature above normal), evaluate aftertreatment conditions that may indicate excess heat reaching the turbo.

Common mistake to avoid

Replacing the EGR valve without testing it. If the valve still moves freely, a carbon cleaning often fixes the flow code; and if it opens on command but the code stays, the blockage is in the passages or cooler, not the valve. Source: FleetRabbit — EGR valve problems and repair.

Parts and tools you may need

Tools you’ll need

Rough cost and difficulty

Likely repairPartsShop laborWho usually does it
EGR valve/passage carbon cleaning$20–$1001–4 hrsDIY with tools and a manual
Intercooler boot, clamp or pipe repair$20–$2000.5–2 hrsEasy DIY
Fuel injector (each)$350–$1,2002–3 hrsShop

Typical US independent-shop figures; labor runs about $140–$200 per hour (dealers charge more). Confirm the diagnosis before buying parts.

When to see a pro

If high-pressure fuel injection system work is required, or if turbocharger removal/replacement is needed, have a qualified diesel technician perform the work. Seek professional help for any safety-critical system diagnosis.

Check for recalls

Recalls are tied to your truck’s VIN, so check yours directly: enter the VIN at NHTSA’s recall lookup. Open safety recalls are repaired free at a dealer.

Sources

  1. Curated DTC seed — Cummins ISX15 (curated) ↩︎ ↩︎ ↩︎ ↩︎