Cummins fault code 4744
DEF Temperature 2 Sensor Circuit: circuit grounded / current high
What it means
Cummins' description: Aftertreatment 1 Diesel Exhaust Fluid Temperature 2 Sensor Circuit - Current above normal or grounded.
SPN 3515 is Aftertreatment 1 Diesel Exhaust Fluid Temperature 2. FMI 6 means too much current is flowing in the circuit, usually a wire rubbed through to ground or a shorted component.
DEF is sprayed into the exhaust ahead of the SCR catalyst to break down NOx. The system includes the tank, level and temperature sensors, a quality sensor, heaters for cold weather, a pump or dosing unit, lines and the doser.
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
The DEF level warning is on and the truck runs normally. Topping off with fresh DEF clears it.
Schedule a repair
Amber lamp or a DEF quality or dosing code that comes back after filling. Get it checked soon. If left alone, the system will start counting down toward a derate.
Stop and get help
Blinking lamp with a derate countdown, or the truck is already limited to low speed. That's an EPA inducement. It won't fix itself and it can leave a truck stuck at 5 mph.
Common causes
FMI 6 is an electrical or signal fault, so start with the circuit:
- Corroded or loose connector at the DEF tank or dosing unit
- Failed DEF level, temperature or quality sensor (often built into one tank header)
- Open or shorted heater circuit or heater relay
- Harness damage near the tank or frame rail
If the circuit checks out, the reading may be real. Other possibilities: dEF tank low or empty; contaminated, diluted or old DEF (water, coolant, diesel, or DEF older than about a year); crystallized DEF clogging the doser, lines or filter.
What you can check before calling
- Check the DEF level and top off with fresh, sealed DEF
- Look for white crystal buildup around the doser, lines and tank
- If DEF was recently added, think about whether it could have been mixed with water or something else
- Note whether the code shows up only in cold weather
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
- 4233 SPN 3515 FMI 3
DEF Temperature 2 Sensor Circuit: circuit voltage high / shorted high - 4234 SPN 3515 FMI 4
DEF Temperature 2 Sensor Circuit: circuit voltage low / shorted low - 4242 SPN 3515 FMI 2
DEF Temperature 2: erratic or intermittent signal - 4243 SPN 3515 FMI 10
DEF Temperature 2 Abnormal Rate of Change: abnormal rate of change - 4743 SPN 3515 FMI 5
DEF Temperature 2 Sensor Circuit: circuit open / current low - 4745 SPN 3515 FMI 11
DEF Temperature 2: root cause not known - 6619 SPN 3515 FMI 10
DEF Temperature 2: abnormal rate of change
Related DEF codes
- 4739 SPN 1761 FMI 11
DEF Tank Level Sensor: root cause not known - 4738 SPN 1761 FMI 6
DEF Tank Level Sensor Circuit: circuit grounded / current high - 4737 SPN 3031 FMI 11
DEF Tank Temperature: root cause not known - 4736 SPN 3031 FMI 6
DEF Tank Temperature Sensor Circuit: circuit grounded / current high - 4752 SPN 520716 FMI 3
DEF Dosing Valve 1 Heater: circuit voltage high / shorted high - 4753 SPN 520716 FMI 4
DEF Dosing Valve 1 Heater: circuit voltage low / shorted low
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 4744 mean?
Cummins fault code 4744 is J1939 SPN 3515 FMI 6: Aftertreatment 1 Diesel Exhaust Fluid Temperature 2 Sensor Circuit - Current above normal or grounded. In plain terms: def temperature 2 sensor circuit: circuit grounded / current high.
Can I keep driving with Cummins code 4744?
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 4744?
SPN 3515 identifies the part or system (Aftertreatment 1 Diesel Exhaust Fluid Temperature 2). FMI 6 describes the type of failure: circuit grounded / current high.
What usually causes Cummins code 4744?
The most common causes are: corroded or loose connector at the DEF tank or dosing unit; failed DEF level, temperature or quality sensor (often built into one tank header); open or shorted heater circuit or heater relay.
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.