Cummins fault code 4585
SCR Catalyst System: special instructions
What it means
Cummins' description: Aftertreatment 1 SCR Catalyst System - Special Instructions.
SPN 4792 is Aftertreatment 1 SCR Catalyst System. FMI 14 means the fault requires specific troubleshooting steps from Cummins service information.
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
Related SCR catalyst and inducement codes
- 4586 SPN 4339 FMI 31
SCR Feedback Control Status: condition exists - 4658 SPN 4331 FMI 18
SCR Actual Dosing Reagent Quantity: reading below normal (moderately severe) - 4489 SPN 5842 FMI 31
SCR Monitoring System Malfunction: condition exists - 4863 SPN 5245 FMI 31
DEF Tank Low Level Indicator: condition exists - 4261 SPN 5743 FMI 11
SCR Temperature Sensor Module: root cause not known - 4166 SPN 5743 FMI 16
SCR Temperature Sensor Module: reading above normal (moderately 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 4585 mean?
Cummins fault code 4585 is J1939 SPN 4792 FMI 14: Aftertreatment 1 SCR Catalyst System - Special Instructions. In plain terms: scr catalyst system: special instructions.
Can I keep driving with Cummins code 4585?
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 4585?
SPN 4792 identifies the part or system (Aftertreatment 1 SCR Catalyst System). FMI 14 describes the type of failure: special instructions.
What usually causes Cummins code 4585?
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.