Cummins fault code 3146
SCR Outlet Temperature Sensor Circuit: circuit voltage high / shorted high
What it means
Cummins' description: Aftertreatment 1 SCR Outlet Temperature Sensor Circuit - Voltage above normal, or shorted to high source.
SPN 4363 is Aftertreatment 1 SCR Catalyst Outlet Gas Temperature. 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 SCR (selective catalytic reduction) catalyst uses DEF to turn NOx into nitrogen and water. The ECM compares NOx before and after the catalyst to judge how well it's working. If it isn't, EPA rules require the engine to warn the driver and then derate.
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 code with no lamp, or the amber lamp clears after a few drive cycles and fresh DEF.
Schedule a repair
Amber lamp with SCR efficiency or NOx codes that keep returning. Schedule diagnosis. These usually get worse, and inducement timers can be running in the background.
Stop and get help
Blinking lamp, inducement countdown, or the engine is already derated to low power or 5 mph. Stop and get it diagnosed. Clearing codes alone won't reset a real inducement.
Common causes
FMI 3 is an electrical or signal fault, so start with the circuit:
- SCR temperature sensor or sensor module failed
- Wiring or connector damage at the catalyst
- NOx sensor reporting bad data
If the circuit checks out, the reading may be real. Other possibilities: bad or diluted DEF, or not enough DEF being dosed; crystallized or clogged DEF doser; failing NOx sensor (very common).
What you can check before calling
- Check DEF level and quality first. It's the cheapest fix
- Look for exhaust leaks or soot tracks at clamps ahead of the catalyst
- Write down any countdown or derate message on the dash before it changes
Clearing the code without fixing the cause usually brings it right back, and on emissions systems it can restart derate timers. For the bigger picture, read our guide: DEF warning lights and derate: what diesel drivers need to know.
Engines and sources
Listed by Cummins for: QSB 6.7, QSL 9, QSX 15, QSB 4.5, QSF 3.8 (With SCR), QSG 12. 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
- 3147 SPN 4363 FMI 4
SCR Outlet Temperature Sensor Circuit: circuit voltage low / shorted low - 3148 SPN 4363 FMI 2
SCR Outlet Temperature Sensor: erratic or intermittent signal - 3165 SPN 4363 FMI 0
SCR Outlet Temperature: reading above normal (most severe) - 3235 SPN 4363 FMI 16
SCR Outlet Temperature: reading above normal (moderately severe) - 6569 SPN 4363 FMI 3
SCR Outlet Temperature Sensor Circuit: circuit voltage high / shorted high - 6571 SPN 4363 FMI 4
SCR Outlet Temperature Sensor Circuit: circuit voltage low / shorted low
Related SCR catalyst and inducement codes
- 3144 SPN 4360 FMI 2
SCR Intake Temperature Sensor: erratic or intermittent signal - 3143 SPN 4360 FMI 4
SCR Intake Temperature Sensor Circuit: circuit voltage low / shorted low - 3142 SPN 4360 FMI 3
SCR Intake Temperature Sensor Circuit: circuit voltage high / shorted high - 3151 SPN 4794 FMI 31
SCR Catalyst System Missing: condition exists - 3164 SPN 4360 FMI 15
SCR Intake Temperature: reading above normal (least severe) - 3229 SPN 4360 FMI 0
SCR Intake Temperature: reading above normal (most severe)
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 3146 mean?
Cummins fault code 3146 is J1939 SPN 4363 FMI 3: Aftertreatment 1 SCR Outlet Temperature Sensor Circuit - Voltage above normal, or shorted to high source. In plain terms: scr outlet temperature sensor circuit: circuit voltage high / shorted high.
Can I keep driving with Cummins code 3146?
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 3146?
SPN 4363 identifies the part or system (Aftertreatment 1 SCR Catalyst Outlet Gas Temperature). FMI 3 describes the type of failure: circuit voltage high / shorted high.
What usually causes Cummins code 3146?
The most common causes are: sCR temperature sensor or sensor module failed; wiring or connector damage at the catalyst; nOx sensor reporting bad data.
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.