Safe to driveTo the nearest safe stop
J1939 code SPN 168. Below — how the fault is worded at the factory by DAF, Dongfeng, International, KAMAZ, MAZ, Mercedes-Benz, Renault Trucks, SITRAK, YaMZ and ZF AS-Tronic, and what the second half of the code (FMI) means in the standard.
DAFDongfengInternationalKAMAZMAZMercedes-BenzRenault TrucksSITRAKYaMZZF AS-Tronic
| FMI 16 | ECU power supply, pin C4 voltage too high (>36V) |
| FMI 18 | ECU power supply, pin C4 voltage too low (<6V) |
| FMI 16 | Battery voltage too high |
| FMI 18 | Battery voltage too low |
| FMI 2 | Electrical Potential (Voltage) — Comm. fault from ESC/BC to PP3. |
| FMI 3 | Electrical Potential (Voltage) — DC Module Overvoltage condition on Vehicle DC Bus.; Electrical Potential (Voltage) — AC Module Overvoltage condition on High Voltage DC Bus.; Electrical Potential (Voltage) — Battery Voltage High |
| FMI 4 | Electrical Potential (Voltage) — DC Module Undervoltage condition on Vehicle DC Bus.; Electrical Potential (Voltage) — AC Module Undervoltage condition on High Voltage DC Bus.; Electrical Potential (Voltage) — Battery Voltage Low |
| FMI 6 | Electrical Potential (Voltage) — AC Module has shutdown due to overload condition. |
| FMI 8 | Electrical Potential (Voltage) — Phase missing fault/alternator fault. |
| FMI 16 | Electrical Potential (Voltage) — DC module over temperature condition.; Electrical Potential (Voltage) — AC module over temperature condition. |
| FMI 17 | Electrical Potential (Voltage) — PPE3 Fuse Open. |
| FMI 3 | Battery supply voltage out of range. K-line code on KamAZ-5490: MR2 17542. |
| FMI 4 | Battery supply voltage out of range. K-line code on KamAZ-5490: MR2 17543. |
| FMI 3 | Battery supply voltage out of range - Battery voltage high. Blink code: 1-2-4. Repair: Check the battery and its wiring. |
| FMI 4 | Battery supply voltage out of range - Battery voltage low. Blink code: 1-2-4. Repair: Check the battery and its wiring. |
| FMI 0 | Coolant Level below operating level (pre-warning condition) |
| FMI 1 | Battery Voltage Very Low |
| FMI 7 | Opt Idle Detected Charging System or Battery Failure |
| FMI 9 | Main battery connection lost |
| FMI 0 | Battery voltage measured by the EECU processor too high. Repair: The alternator regulator is faulty. |
| FMI 1 | Battery voltage measured by the EECU processor too low. Repair: The alternator or the batteries are faulty. |
| FMI 3 | Battery voltage measured by the control unit above 40 V. Repair: If the voltage is normal, replace the EECU. |
| FMI 4 | Battery voltage measured by the control unit below 5.5 V. Repair: If the voltage is normal, replace the EECU. |
| FMI 8 | Pedal released contact, erroneous signal. Repair: Check that the accelerator pedal position changes correctly. Run the diagnostic check of the EECU. Check the programming. Switch the ignition off, switch it on again and repeat the test. If the fault persists, replace the control unit. |
| FMI 12 | Battery voltage reading fault. Repair: Replace the EECU. |
| FMI 15 | Battery voltage measured by the EECU processor too high. Repair: The alternator regulator is faulty. |
| FMI 17 | Battery voltage measured by the EECU processor too high. Repair: The alternator or the batteries are faulty. |
| FMI 3 | System voltage above the upper limit for the actuator supply. Scan tool code: P0563. Effect: OBD limits torque immediately. |
| FMI 4 | System voltage below the lower limit for the actuator supply. Scan tool code: P0562. |
| FMI 15 | High battery voltage |
| FMI 17 | Low battery voltage |
| FMI 3 | Battery supply voltage out of range (Battery voltage high). Blink code: 1-2-4. Repair: Check the battery and its wiring. |
| FMI 4 | Battery supply voltage out of range (Battery voltage low). Blink code: 1-2-4. Repair: Check the battery and its wiring. |
ZF AS-Tronic uses its own fault numbering: the number in the table below is an internal ZF code, not a J1939 SPN. It matches the title of this page by digit only and means something different.
| FMI 8 | No idle signal from the electronic accelerator pedal. |
Safe to drive. Below — how much time you have and what happens if you keep going.
The electrical system is not holding voltage. While the engine runs the alternator carries it; shut it off and you may not restart.
Next the lights go, then modules start dropping out and false codes appear all over the truck. Get to somewhere with help without shutting the engine down.
That said, the manufacturer flags this code as critical — if in doubt, it is safer to stop and check on the spot.
Check the battery terminals and earth strap — corrosion and loose clamps throw false codes all over the truck. Running voltage should be 27–29 V.
Scanner threw several codes at once? Paste the whole list — we will show which one is the root cause and which ones simply followed.