Cummins fault code 694

What it means

Cummins' description: RBF Turbo Comp Inlet Temp Sens Failed High.

SPN 1173 is RBF Turbo Comp Inlet Temp Sens Failed High. FMI 3 means the voltage on the circuit is higher than possible for a good sensor, usually an open signal wire, a short to a power wire, or a failed sensor.

The turbocharger forces air into the engine. Most modern Cummins engines use a variable geometry turbo (VGT) with an electronic actuator. The ECM watches intake manifold pressure, turbo speed and compressor temperatures to control boost.

What the lamp means

This code normally doesn't turn on a dash lamp. It's logged in the ECM for a technician to see, and often explains another active code.

Common causes

FMI 3 is an electrical or signal fault, so start with the circuit:

• VGT actuator internal fault or wiring problem (common)
• Boost or intake manifold pressure sensor failed or plugged
• Turbo speed sensor or wiring fault
• Actuator power, ground or network connection problem

If the circuit checks out, the reading may be real. Other possibilities: boost leak: split charge air hose, loose clamp, cracked charge air cooler; vGT vanes sticking from soot; worn or damaged turbo.

What you can check before calling

• Listen for a new hiss or whistle under load, a typical sign of a boost leak
• Check charge air hoses and clamps for oil or soot
• Check the air filter restriction indicator
• Notice whether power loss happens only under heavy load or on hills

Clearing the code without fixing the cause usually brings it right back, and on emissions systems it can restart derate timers.

Engines and sources

Cummins uses the same fault code numbers across its electronic engines, including on-highway models like the ISB/B6.7, ISL/L9 and ISX/X15, though not every code applies to every engine or software level. Source: Diagnostic Fault Codes for Cummins Engines. Always confirm with Cummins service information (QuickServe) for your engine serial number.