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SPN 1074 — Engine Brake Output (Exhaust Damper)

Safe to driveEnough to reach the yard

J1939 code SPN 1074. Below — how the fault is worded at the factory by Dongfeng, Ford Trucks, KAMAZ, MAZ, Renault Trucks, SITRAK and YaMZ, and what the second half of the code (FMI) means in the standard.

DongfengFord TrucksKAMAZMAZRenault TrucksSITRAKYaMZ

Dongfeng

FMI 3Short circuit to power or open circuit at the hill-hold (mountain) brake output. Scan tool code: P1098. Effect: Torque may be limited.
FMI 4Short circuit to ground at the hill-hold (mountain) brake output

Ford Trucks

Ford Trucks/Ecotorq writes fault numbers in its own format: the code in the table below is a Ford code (hexadecimal, zero-padded), not a J1939 SPN. It matches the standard only where the signal itself is standard, and usually matches the title of this page by digit alone.

FMI 3Connector or wiring harness defective (short circuit between AIM2 and VPSx), activation solenoid valve (magnetic coil) defective, IT-ECU output efective
FMI 5Connector or wiring harness defective (interrupt AIM2/VPS2), activation solenoid valve (magnetic coil) defective, IT-ECU output efective
FMI 6Connector or wiring harness defective (short circuit between AIM2 and VMGx/vehicle ground), activation solenoid valve (magnetic coil) defective, IT-ECU output efective
FMI 14Single error: Activation solenoid valve (magnetic coil)defective. In combination with “Short circuit or inductance error of proportional solenoid valve”: Connector or wiring harness defective (short circuit between AIM2 and AIM1).

KAMAZ

FMI 2Engine brake exhaust flap: short circuit / open circuit / overheating
FMI 3Engine brake exhaust flap: short circuit / open circuit / overheating. K-line code on KamAZ-5490: ADM3 14603.
FMI 4Engine brake exhaust flap: short circuit / open circuit / overheating. K-line code on KamAZ-5490: ADM3 14604.
FMI 12Engine brake exhaust flap: short circuit / open circuit / overheating. K-line code on KamAZ-5490: MR2 14254.

MAZ

FMI 2Exhaust (mountain) brake valve control error - Overheating. Blink code: 6-9-1. Repair: Check the exhaust brake flap control valve and its wiring.
FMI 3Exhaust (mountain) brake valve control error - Short to battery positive. Blink code: 6-9-1. Repair: Check the exhaust brake flap control valve and its wiring.
FMI 4Exhaust (mountain) brake valve control error - Short to ground. Blink code: 6-9-1. Repair: Check the exhaust brake flap control valve and its wiring.
FMI 12Exhaust (mountain) brake valve control error - Open circuit. Blink code: 6-9-1. Repair: Check the exhaust brake flap control valve and its wiring.

Renault Trucks

FMI 3Exhaust brake (WABCO) — short to battery positive. Repair: Check the solenoid valve and the wiring (J 2/21). Check the solenoid valve and the wiring (B 9, B 22, B 42).
FMI 4Exhaust brake (WABCO) — short to ground. Repair: Check the solenoid valve and the wiring (J 2/21). Check the solenoid valve and the wiring (B 9, B 22, B 42).
FMI 5Exhaust brake (WABCO) — open circuit. Repair: Check the solenoid valve and the wiring (J 2/21). Check the solenoid valve and the wiring (B 9, B 22, B 42).

SITRAK

FMI 0Persistent positive governor deviation of the exhaust brake flap. Scan tool code: P1096. Effect: The engine brake is disabled.
FMI 1Persistent negative governor deviation of the exhaust brake flap downstream of the turbine. Scan tool code: P1096. Effect: Torque may be limited.
FMI 2Exhaust flap feedback sensor voltage above the upper limit. Scan tool code: P1098. Effect: Torque may be limited.
FMI 3Exhaust flap feedback sensor voltage below the lower limit. Scan tool code: P1098. Effect: Torque may be limited.

YaMZ

FMI 2Mountain brake valve control fault (Overheating). Blink code: 6-9-1. Repair: Check the exhaust brake flap control valve and its wiring.
FMI 3Mountain brake valve control fault (Short to battery positive). Blink code: 6-9-1. Repair: Check the exhaust brake flap control valve and its wiring.
FMI 4Mountain brake valve control fault (Short to ground). Blink code: 6-9-1. Repair: Check the exhaust brake flap control valve and its wiring.
FMI 12Mountain brake valve control fault (Open circuit). Blink code: 6-9-1. Repair: Check the exhaust brake flap control valve and its wiring.

What FMI means in J1939

SPN 1074 FMI 01074/0 · 1074.0data above normal range (most severe level)
SPN 1074 FMI 11074/1 · 1074.1data below normal range (most severe level)
SPN 1074 FMI 21074/2 · 1074.2data erratic or intermittent
SPN 1074 FMI 31074/3 · 1074.3voltage above normal or shorted high
SPN 1074 FMI 41074/4 · 1074.4voltage below normal or shorted to ground
SPN 1074 FMI 51074/5 · 1074.5current below normal or open circuit
SPN 1074 FMI 61074/6 · 1074.6current above normal or grounded circuit
SPN 1074 FMI 121074/12 · 1074.12faulty device or component
SPN 1074 FMI 141074/14 · 1074.14manufacturer-specific instructions

Can I keep driving

Safe to drive. Below — how much time you have and what happens if you keep going.

What happens if you keep driving

Time you have: Enough to reach the yard

Urea dosing is interrupted and the ECU is counting. First the lamp, then a torque cut, then a forced crawl speed — the stages come in by engine hours, not all at once.

The truck will not die mid-highway, but the window shrinks with every running hour. Plan the repair now, not when the power is gone: an emulator or "deleting AdBlue" does not remove the problem, the codes keep stacking.

That said, the manufacturer flags this code as critical — if in doubt, it is safer to stop and check on the spot.

What to check on the spot

Fill the AdBlue tank. If it’s already full, the problem is dosing or reductant quality — you need a scanner.

Nearby: AdBlue / exhaust

Scanner threw several codes at once? Paste the whole list — we will show which one is the root cause and which ones simply followed.