Updated: 2026-11-14
Safe to driveDrivable, but watch it yourself
J1939 code SPN 558. Below — how the fault is worded at the factory by Cummins ISB, DAF, KAMAZ-5490, Mercedes-Benz, Renault Trucks and SITRAK, and what the second half of the code (FMI) means in the standard.
The idle switch on the accelerator pedal — a contact that tells the ECU "pedal released". The ECU checks it against the pedal sensor (SPN 91).
| Pedal released | contact in one position |
| Pedal slightly pressed | switches at the very start of travel |
Cummins ISBDAFKAMAZ-5490Mercedes-BenzRenault TrucksSITRAK
| FMI 9 | Accelerator pedal idle validation switch abnormal update rate |
| FMI 19 | Accelerator pedal idle validation switch network data error |
| FMI 2 | Accelerator pedal idle switch signal fault |
| FMI 4 | Accelerator pedal voltage too low at ECU pin B1/B11 |
| FMI 13 | Accelerator pedal not calibrated, out of tolerance |
FMI is per the block maker's own table, not the J1939 table below.
| FMI 1 | Accelerator pedal idle switch (GAS1, GAS2 or J1939): both signals equal but must differ. K-line code on KamAZ-5490: ADM3 11701. |
| FMI 5 | Accelerator pedal idle switch (GAS1, GAS2 or J1939): both switch circuits open. K-line code on KamAZ-5490: ADM3 11705. |
| FMI 9 | Accelerator pedal idle switch (GAS1, GAS2 or J1939): CAN message update rate abnormal. K-line code on KamAZ-5490: ADM3 11709. |
| FMI 12 | Accelerator pedal idle switch (GAS1, GAS2 or J1939): both switch circuits closed. K-line code on KamAZ-5490: ADM3 11712. |
| FMI 19 | Accelerator pedal idle switch (GAS1, GAS2 or J1939): erroneous data received over CAN. K-line code on KamAZ-5490: ADM3 11719. |
| FMI 2 | Idle Validation Switch Inputs Reversed |
| FMI 3 | Idle Validation Switch 1 Circuit shorted to Ubat |
| FMI 4 | Idle Validation Switch 1 Circuit shorted to GND |
| FMI 6 | Idle Validation Switch 2 Circuit shorted to ground |
| FMI 7 | “Accelerator pedal released” contact stuck closed or open. Repair: Check the continuity of the link on pins 3 and 4 of the pedal unit with the pedal released, press the pedal and check that the state changes; if it does, check the wiring (SL2/1). |
| FMI 2 | Accelerator pedal and idle switch signals do not match. Scan tool code: P2135. |
Safe to drive. Below — how much time you have and what happens if you keep going.
This is an electrical fault: an open, a short or a bad contact in the sensor circuit. The value it measures is most likely fine.
You can drive. But until the circuit is repaired this system runs blind and cannot warn you about a real failure.
SPN 558 is the accelerator pedal idle validation (limit) switch. Electronic pedals have two ways to prove the driver has lifted the foot: the position sensor reads a low value, and a switch closes at idle. The computer compares them. If they disagree, it records SPN 558 or SPN 91 and may limit power.
1. In the scan tool watch pedal position and the idle switch status while you press and release slowly. The switch should change state right at the start of travel.
2. If the switch stays set, or the sensor shows a value with the foot off, the pedal is out of adjustment, worn or dirty.
3. Check the pedal connector for corrosion and for a loose latch.
4. Look for an obstruction under the pedal, such as a floor mat, and the pedal stop.
5. If the pedal was replaced recently, check whether it needs a learning or calibration procedure.
Replace the pedal assembly if the sensor and switch cannot be brought to agree, since they are normally one part.
The engine usually goes to idle or to limited throttle. That is not safe in traffic. Drive slowly to the nearest stop and call for service.
SPN 91 is the pedal position sensor. SPN 558 is the idle switch that confirms that sensor. Both are often logged together.
A mat can stop the pedal from returning fully, so the idle switch never closes.
Scanner threw several codes at once? Paste the whole list — we will show which one is the root cause and which ones simply followed.