Cummins fault code 784
Adaptive Cruise Control Mode: erratic or intermittent signal
What it means
Cummins' description: Adaptive Cruise Control Mode - Data erratic, intermittent or incorrect.
SPN 1590 is Adaptive Cruise Control Mode. FMI 2 means the signal is jumping around, dropping in and out, or doesn't make sense compared to other readings.
The accelerator pedal has position sensors and an idle validation switch so the ECM knows exactly what the driver is asking for. Cruise control, brake and clutch switches, PTO and vehicle speed inputs are also monitored.
What the lamp means
This code normally doesn't turn on a dash lamp. It's logged in the ECM for a technician to see, and often explains another active code.
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 pedal or switch code that set once and cleared, and the pedal works normally.
Schedule a repair
Cruise doesn't work, the pedal feels dead in spots, or the code keeps returning. Have the pedal or switch checked.
Stop and get help
Engine stuck at idle or the pedal not responding, especially with a red lamp. Don't drive it in traffic. You won't have reliable throttle.
Common causes
The sensor reading itself is out of range or the condition is real, so look at the system:
- Pedal sensors disagreeing with each other
- Switch inputs that don't make sense together, like brake and throttle at once
What you can check before calling
- Check whether the engine stays at idle no matter what you do with the pedal
- Look at the pedal connector under the dash
- Check whether cruise control works
Clearing the code without fixing the cause usually brings it right back, and on emissions systems it can restart derate timers.
Engines and sources
Listed by Cummins for: 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.
Related Accelerator pedal and driver controls codes
- 771 SPN 597 FMI 4
Brake Switch Circuit: circuit voltage low / shorted low - 769 SPN 597 FMI 3
Brake Switch Circuit: circuit voltage high / shorted high - 551 SPN 558 FMI 4
Accelerator Pedal Idle Validation Circuit: circuit voltage low / shorted low - 489 SPN 191 FMI 18
Transmission Output Shaft Speed: reading below normal (moderately severe) - 443 SPN 1043 FMI 4
Accelerator Pedal Position Sensor Supply Voltage Circuit: circuit voltage low / shorted low - 432 SPN 558 FMI 13
Accelerator Pedal or Lever Idle Validation Switch Circuit: out of calibration
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 784 mean?
Cummins fault code 784 is J1939 SPN 1590 FMI 2: Adaptive Cruise Control Mode - Data erratic, intermittent or incorrect. In plain terms: adaptive cruise control mode: erratic or intermittent signal.
Can I keep driving with Cummins code 784?
Usually, yes. This code doesn't normally turn on a lamp by itself, but check for other active codes that might be more serious. Look at the green, yellow and red examples on this page to judge your situation.
What is the SPN and FMI for Cummins code 784?
SPN 1590 identifies the part or system (Adaptive Cruise Control Mode). FMI 2 describes the type of failure: erratic or intermittent signal.
What usually causes Cummins code 784?
The most common causes are: pedal sensors disagreeing with each other; switch inputs that don't make sense together, like brake and throttle at once.
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.