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SPN 172 — Intake air temperature

Safe to driveEnough to reach the yard

J1939 code SPN 172. Below — how the fault is worded at the factory by Isuzu, KAMAZ, MAZ, SITRAK and YaMZ, and what the second half of the code (FMI) means in the standard.

IsuzuKAMAZMAZSITRAKYaMZ

Isuzu

FMI 3Intake air temperature sensor fault (high voltage fault) (P0113)
FMI 4Intake air temperature sensor fault (low voltage fault) (P0112)

KAMAZ

FMI 3Air flow sensor: air temperature sensor
FMI 4Air flow sensor: air temperature sensor

MAZ

FMI 3Mass air flow sensor temperature element error - Voltage above allowed. Blink code: 2-3-4. Repair: Check the mass air flow sensor and its wiring.
FMI 4Mass air flow sensor temperature element error - Voltage below allowed. Blink code: 2-3-4. Repair: Check the mass air flow sensor and its wiring.

SITRAK

FMI 0Short circuit in the intake air heater grid circuit. Scan tool code: P0113.
FMI 1Intake air heater grid circuit short to ground. Scan tool code: P0112.
FMI 2Implausible charge air cooler downstream temperature sensor signal. Scan tool code: P007A. Effect: Torque limited, black smoke.
FMI 3Charge air cooler downstream temperature sensor voltage above the upper limit. Scan tool code: P007A. Effect: Torque limited, black smoke.
FMI 4Charge air cooler downstream temperature sensor voltage below the lower limit. Scan tool code: P007A. Effect: Torque limited, black smoke.
FMI 10Fault in the low-pressure charge air cooler downstream temperature sensor. Scan tool code: P007A. Effect: Torque limited, black smoke.
FMI 15Short circuit in the intake air heater grid circuit. Scan tool code: P0113.
FMI 17Intake air heater grid circuit short to ground. Scan tool code: P0112.

YaMZ

FMI 3Mass air flow sensor temperature element fault (Voltage above allowable limit). Blink code: 2-3-4. Repair: Check the mass air flow sensor and its wiring.
FMI 4Mass air flow sensor temperature element fault (Voltage below allowable limit). Blink code: 2-3-4. Repair: Check the mass air flow sensor and its wiring.

What FMI means in J1939

SPN 172 FMI 0172/0 · 172.0data above normal range (most severe level)
SPN 172 FMI 1172/1 · 172.1data below normal range (most severe level)
SPN 172 FMI 2172/2 · 172.2data erratic or intermittent
SPN 172 FMI 3172/3 · 172.3voltage above normal or shorted high
SPN 172 FMI 4172/4 · 172.4voltage below normal or shorted to ground
SPN 172 FMI 10172/10 · 172.10abnormal rate of change
SPN 172 FMI 15172/15 · 172.15above normal — low severity
SPN 172 FMI 17172/17 · 172.17below normal — low severity

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

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.

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

Inspect the air filter and charge-air hoses: leaks and cracks produce exactly these codes.

Nearby: intake / boost

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