Do not driveMinutes
J1939 code SPN 1639. Below — how the fault is worded at the factory by KAMAZ, MAZ, Renault Trucks, SITRAK and YaMZ, and what the second half of the code (FMI) means in the standard.
KAMAZMAZRenault TrucksSITRAKYaMZ
| FMI 3 | Fan speed sensor |
| FMI 4 | Fan speed sensor |
| FMI 3 | Fan speed sensor circuit fault - Short to battery positive. Blink code: 3-1-2. Repair: Check the speed sensor and its wiring. |
| FMI 4 | Fan speed sensor circuit fault - Short to ground. Blink code: 3-1-2. Repair: Check the speed sensor and its wiring. |
| FMI 0 | Fan speed above 322 Hz and below 408 Hz. Repair: Check the fan and the wiring (J 2/4, J 2/7, J 2/18, J 2/40). |
| FMI 2 | Fan, open circuit with the engine running. Repair: Check the fan and the wiring (J 2/4, J 2/7, J 2/18, J 2/40). |
| FMI 3 | Fan speed sensor — speed above 408 Hz, or short to battery positive. Repair: Check the fan and the wiring (J 2/4, J 2/7, J 2/18, J 2/40). Check the sensor and the wiring (B 4, B 9, B 14, B 22, B 23, B 34). |
| FMI 12 | Fan speed sensor: open circuit, short to battery voltage or short to ground. Repair: Check the fan hub and the wiring (B 4, B 9, B 14, B 22, B 23, B 34). |
| FMI 15 | Fan speed above normal. Repair: Check the wiring (B 4, B 9, B 14, B 22, B 23, B 34). |
| FMI 16 | Fan speed sensor, sensor supply voltage too high. Repair: Check the sensor, the electronic control unit and the wiring (B 4, B 9, B 14, B 22, B 23, B 34). |
| FMI 18 | Fan speed sensor, sensor supply voltage too low. Repair: Check the sensor, the electronic control unit and the wiring (B 4, B 9, B 14, B 22, B 23, B 34). |
| FMI 0 | DPF soot mass deviation, measured against modelled, below the minimum level. Scan tool code: P242F. Effect: Torque may be limited. |
| FMI 2 | Fan speed signal missing on the CAN bus. Effect: The engine may overheat or use more fuel. |
| FMI 3 | Fan speed too high. Scan tool code: P0495. Effect: The engine may overheat or use more fuel. |
| FMI 4 | Fan speed too low. Scan tool code: P0494. Effect: The engine may overheat or use more fuel. |
| FMI 5 | Open load in the fan speed signal circuit. Scan tool code: P0526. Effect: The engine may overheat or use more fuel. |
| FMI 8 | Fan speed sensor frequency signal period too long. Scan tool code: P0480. Effect: The engine may overheat or use more fuel. |
| FMI 22 | Intermittent fault or loose connection in the fan speed signal circuit. Scan tool code: P0526. Effect: The engine may overheat or use more fuel. |
| FMI 3 | Fan speed sensor circuit fault (Short to battery positive). Blink code: 3-1-2. Repair: Check the speed sensor and its wiring. |
| FMI 4 | Fan speed sensor circuit fault (Short to ground). Blink code: 3-1-2. Repair: Check the speed sensor and its wiring. |
Do not drive. Stop as soon as it’s safe to do so — don’t keep going.
The engine is already past its temperature limit. An aluminium head goes fast: first the geometry warps, then the gasket burns through.
Next comes a blown head gasket, a damaged head and, at worst, a cracked block. Shut it down and let it cool — never open the expansion tank cap while hot.
This is an electrical fault: the sensor or its wiring is lying, not the cooling system. The temperature gauge is unreliable now and the fan may not kick in on time. Watch the coolant level and keep the engine off load on long climbs.
Let the engine cool — never open the expansion tank cap while hot. Then check the level and the hoses.
Scanner threw several codes at once? Paste the whole list — we will show which one is the root cause and which ones simply followed.