Cummins fault code 551
Accelerator Pedal Idle Validation Circuit: circuit voltage low / shorted low
What it means
Cummins' description: Accelerator Pedal Idle Validation Circuit - shorted low.
SPN 558 is Accelerator Pedal Idle Validation Circuit. FMI 4 means the voltage on the circuit is lower than possible for a good sensor, usually a short to ground, a damaged harness, or a failed sensor.
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
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 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
FMI 4 is an electrical or signal fault, so start with the circuit:
- Accelerator pedal sensor worn or failed
- Pedal connector corroded or loose
- Brake, clutch or cruise switch out of adjustment or failed
- Vehicle speed sensor or wiring fault
If the circuit checks out, the reading may be real. Other possibilities: 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
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: Diagnostic Fault Codes for Cummins Engines. Always confirm with Cummins service information (QuickServe) for your engine serial number.
- Older Cummins engines may report this code as SPN 91 FMI 4 (Accelerator Pedal Idle Validation Circuit - shorted low).
Same SPN, other failure types
- 431 SPN 558 FMI 2
Accelerator Pedal or Lever Idle Validation Switch: erratic or intermittent signal - 432 SPN 558 FMI 13
Accelerator Pedal or Lever Idle Validation Switch Circuit: out of calibration - 3527 SPN 558 FMI 19
Accelerator Pedal or Lever Idle Validation Switch: network data error - 3528 SPN 558 FMI 9
Accelerator Pedal or Lever Idle Validation Switch: abnormal update rate
Related Accelerator pedal and driver controls codes
- 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 - 387 SPN 1043 FMI 3
Accelerator Pedal Position Sensor Supply Voltage Circuit: circuit voltage high / shorted high - 349 SPN 191 FMI 16
Transmission Output Shaft Speed: reading above normal (moderately severe) - 769 SPN 597 FMI 3
Brake Switch Circuit: circuit voltage high / shorted high - 771 SPN 597 FMI 4
Brake Switch Circuit: 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 551 mean?
Cummins fault code 551 is J1939 SPN 558 FMI 4: Accelerator Pedal Idle Validation Circuit - shorted low. In plain terms: accelerator pedal idle validation circuit: circuit voltage low / shorted low.
Can I keep driving with Cummins code 551?
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 551?
SPN 558 identifies the part or system (Accelerator Pedal Idle Validation Circuit). FMI 4 describes the type of failure: circuit voltage low / shorted low.
What usually causes Cummins code 551?
The most common causes are: accelerator pedal sensor worn or failed; pedal connector corroded or loose; brake, clutch or cruise switch out of adjustment or failed.
Diesel down in the Midlands?
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