Cummins fault code 3165
SCR Outlet Temperature: reading above normal (most severe)
What it means
Cummins' description: Aftertreatment 1 SCR Outlet Temperature - Data valid but above normal operational range - Most Severe.
SPN 4363 is Aftertreatment 1 SCR Catalyst Outlet Gas Temperature. FMI 0 means the sensor is working, but the value it reports is far above where it should be. This is the most severe 'high' level.
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
A red stop lamp means Cummins treats this as serious. Stop the engine as soon as you can do it safely and get it checked before running it again.
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. Cummins rates this a red stop lamp code, so if the red lamp is on, go by the red 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
The sensor reading itself is out of range or the condition is real, so look at the system:
- Bad or diluted DEF, or not enough DEF being dosed
- Crystallized or clogged DEF doser
- Failing NOx sensor (very common)
- SCR catalyst contaminated by oil or fuel, or worn out
- Exhaust leak ahead of the sensors
- Upstream engine problem raising NOx: EGR fault, boost leak
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
- 3146 SPN 4363 FMI 3
SCR Outlet Temperature Sensor Circuit: circuit voltage high / shorted high - 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 - 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
- 3164 SPN 4360 FMI 15
SCR Intake Temperature: reading above normal (least severe) - 3151 SPN 4794 FMI 31
SCR Catalyst System Missing: condition exists - 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 - 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 3165 mean?
Cummins fault code 3165 is J1939 SPN 4363 FMI 0: Aftertreatment 1 SCR Outlet Temperature - Data valid but above normal operational range - Most Severe. In plain terms: scr outlet temperature: reading above normal (most severe).
Can I keep driving with Cummins code 3165?
No. Cummins assigns this code a red stop lamp. Stop the engine as soon as it's safe and have it checked before running it again. Look at the green, yellow and red examples on this page to judge your situation.
What is the SPN and FMI for Cummins code 3165?
SPN 4363 identifies the part or system (Aftertreatment 1 SCR Catalyst Outlet Gas Temperature). FMI 0 describes the type of failure: reading above normal (most severe).
What usually causes Cummins code 3165?
The most common causes are: bad or diluted DEF, or not enough DEF being dosed; crystallized or clogged DEF doser; failing NOx sensor (very common).
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.