Cummins fault code 2398
Ambient Air Temperature: erratic or intermittent signal
What it means
Cummins' description: Ambient Air Temperature - Data erratic, intermittent or incorrect.
SPN 171 is Ambient Air Temperature. FMI 2 means the signal is jumping around, dropping in and out, or doesn't make sense compared to other readings.
These sensors measure the air coming into the engine: intake manifold temperature, charge air cooler outlet temperature, ambient temperature, barometric pressure, humidity and air filter restriction. The ECM uses them to calculate fueling and timing.
What the lamp means
An amber (yellow) warning lamp means the engine can usually keep running, but the fault should be repaired soon, ideally the same day.
Green, yellow, red: three ways this can look
The same code can be a quick fix or a reason to shut down. Match your situation to the closest example.
Keep an eye on it
A one-time sensor code with normal power and temperatures.
Schedule a repair
Amber lamp, rough cold starts, or the code returns. Usually a sensor or connector. Book it so fueling stays correct.
Stop and get help
Several sensor codes at once with a stop lamp or no-start. That can point to a shared sensor supply or ECM problem. Get it diagnosed before driving.
Common causes
The sensor reading itself is out of range or the condition is real, so look at the system:
- Clogged air filter
- Dirty or blocked charge air cooler or radiator fins
- Real high intake temperature in hot weather or under heavy load
- Boost leak changing intake readings
What you can check before calling
- Check the air filter and the restriction indicator
- Clean bugs and debris from the front of the charge air cooler
- Look for unplugged or damaged connectors on intake sensors
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: Cummins Tier 4 Fault Codes. Always confirm with Cummins service information (QuickServe) for your engine serial number.
Same SPN, other failure types
- 249 SPN 171 FMI 3
Ambient Air Temperature Sensor 1 Circuit: circuit voltage high / shorted high - 256 SPN 171 FMI 4
Ambient Air Temperature Sensor 1 Circuit: circuit voltage low / shorted low - 3531 SPN 171 FMI 9
Ambient Air Temperature: abnormal update rate - 3532 SPN 171 FMI 19
Ambient Air Temperature: network data error
Related Intake air and environment sensors codes
- 2571 SPN 2630 FMI 3
Engine Charge Air Cooler Outlet Temperature: circuit voltage high / shorted high - 2572 SPN 2630 FMI 4
Engine Charge Air Cooler Outlet Temperature: circuit voltage low / shorted low - 1943 SPN 3555 FMI 17
Ambient Air Density: reading below normal (least severe) - 2964 SPN 105 FMI 15
Intake Manifold 1 Temperature: reading above normal (least severe) - 3341 SPN 107 FMI 16
Engine Air Filter Differential Pressure: reading above normal (moderately severe) - 3367 SPN 4490 FMI 9
Specific Humidity Sensor: abnormal update rate
Look up another code
Cummins fault code (like 1922), J1939 SPN and FMI (like SPN 3251 FMI 0), or an OBD-II code (like P0420).
Questions
What does Cummins fault code 2398 mean?
Cummins fault code 2398 is J1939 SPN 171 FMI 2: Ambient Air Temperature - Data erratic, intermittent or incorrect. In plain terms: ambient air temperature: erratic or intermittent signal.
Can I keep driving with Cummins code 2398?
Usually for a short time, if the engine runs normally and no other warnings are on. Get it diagnosed soon, because many amber codes lead to a derate if ignored. Look at the green, yellow and red examples on this page to judge your situation.
What is the SPN and FMI for Cummins code 2398?
SPN 171 identifies the part or system (Ambient Air Temperature). FMI 2 describes the type of failure: erratic or intermittent signal.
What usually causes Cummins code 2398?
The most common causes are: clogged air filter; dirty or blocked charge air cooler or radiator fins; real high intake temperature in hot weather or under heavy load.
Diesel down in the Midlands?
We work on Cummins-powered pickups, vans and medium-duty trucks across Lexington, Columbia and the Midlands, on site at your yard or roadside.