International SA 33 SPN 520727 FMI 2: Auxiliary Switch Error

SA 33 SPN 520727 FMI 2 on International / Navistar trucks means: Auxiliary Switch Error. The failure mode (FMI 2) is “data erratic, intermittent or incorrect”.

Code details

Manufacturer: International (Navistar)
Applies to: International / Navistar body controller (ESC) and multiplexed modules
Fault code: SA 33 SPN 520727 FMI 2
J1939 SPN: 520727
FMI: 2 — Data erratic, intermittent or incorrect
Reporting module: Body Controller (source address 33)
Component / signal: Trailer Auxiliary Power Switch
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: EGC_Digital_Input_1

Cause and when it sets

Cause: Faulty Switch Actuator or Micro switch for Auxiliary Trailer Switch

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 2 tells the shop the type of failure to test for: data erratic, intermittent or incorrect.
Have a heavy-duty diesel technician confirm the fault against the engine or chassis service manual before replacing parts.