International SA 33 SPN 520728 FMI 5: Trailer Left Turn Lamp Relay Under Current Or Open Circuit

SA 33 SPN 520728 FMI 5 on International / Navistar trucks means: Trailer Left Turn Lamp Relay Under Current Or Open Circuit. The failure mode (FMI 5) is “current below normal or open circuit”.

Code details

Manufacturer: International (Navistar)
Applies to: International / Navistar body controller (ESC) and multiplexed modules
Fault code: SA 33 SPN 520728 FMI 5
J1939 SPN: 520728
FMI: 5 — Current below normal or open circuit
Reporting module: Body Controller (source address 33)
Component / signal: Trailer Left Turn Light Relay Command
Truck models in source: 3200, 4100, 4300, 4400, 7300, 7400, 7500, 7600, 7700, 8500, 8600, BE 200, CE Bus, CXT, DuraStar, LoneStar, MXT, ProStar, RXT, TranStar, WorkStar
Logical signal: Trailer_Left_Light

Cause and when it sets

Cause: Open Circuit in Trailer Left Turn Lamp Circuit

What to do next

Read active and inactive codes with the OEM service tool (Diamond Logic Builder can clear previously active codes) and note the occurrence count.
FMI 5 tells the shop the type of failure to test for: current below normal or open circuit.
Have a heavy-duty diesel technician confirm the fault against the engine or chassis service manual before replacing parts.