Safe to driveEnough to reach the yard
J1939 code SPN 729. Below — how the fault is worded at the factory by DAF, Dongfeng, KAMAZ, MAZ, Renault Trucks and YaMZ, and what the second half of the code (FMI) means in the standard.
DAFDongfengKAMAZMAZRenault TrucksYaMZ
| FMI 3 | Preheating relay G014 short to power supply/open circuit at ECU pin B54 |
| FMI 4 | Preheating relay G014 short to ground at ECU pin B54 |
| FMI 3 | Fan control output short circuit to ground |
| FMI 4 | Short circuit to power or open circuit of the heating relay output |
| FMI 3 | Air heater power stage: short circuit. K-line code on KamAZ-5490: ADM3 14003. |
| FMI 4 | Air heater power stage: short circuit. K-line code on KamAZ-5490: ADM3 14004. |
| FMI 3 | Intake air pre-heater driver circuit fault - Short to battery positive. Blink code: 3-2-1. Repair: Check the air preheater and its wiring. |
| FMI 4 | Intake air pre-heater driver circuit fault - Short to ground. Blink code: 3-2-1. Repair: Check the air preheater and its wiring. |
| FMI 11 | Intake air preheating: VECU protection not operative. Repair: Check the continuity and insulation of the wiring (SL2/9), check relays R15 and R16. |
| FMI 3 | Intake air preheater driver circuit fault (Short to battery positive). Blink code: 3-2-1. Repair: Check the air preheater and its wiring. |
| FMI 4 | Intake air preheater driver circuit fault (Short to ground). Blink code: 3-2-1. Repair: Check the air preheater and its wiring. |
| SPN 729 FMI 3729/3 · 729.3 | voltage above normal or shorted high |
| SPN 729 FMI 4729/4 · 729.4 | voltage below normal or shorted to ground |
| SPN 729 FMI 11729/11 · 729.11 | root cause not known |
Safe to drive. Below — how much time you have and what happens if you keep going.
Boost is not reaching its target: turbo, intercooler or intake. The engine compensates with mixture and runs hotter than usual.
You will lose pull, burn more fuel and add overheating on long climbs. If you hear a whine or a whistle from the turbo, stop — the wheel is breaking up.
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.
Inspect the air filter and charge-air hoses: leaks and cracks produce exactly these codes.
Scanner threw several codes at once? Paste the whole list — we will show which one is the root cause and which ones simply followed.