Network, generic (extended)
U3545 High Voltage System Interlock Circuit P
Check engine lightOn
EmissionsNot relevant
Drive cycleNot required
Limp modePossible
U3545 is the general fault code for interlock circuit P, the fifteenth loop. Interlock electronics can be harmed by events elsewhere in the drive. Allison service letter SIL 3-EP-14 (Rev. C, 2017) for the H 40/50 EP hybrid system used in buses offers a separate HVIL circuit card for the DPIM2 inverter: if the check list shows 3 to 4 µF between DC+ or DC− and chassis, for example after an internal stator short, that card is damaged and can be swapped instead of the whole inverter, which first has to come out of the vehicle; an ESD wrist strap is mandatory. No maker documents U3545.
Likely causes
Interlock circuit board inside the inverter damaged, e.g. after a motor winding short
Connector in loop P not fully latched
Loop P wiring damaged
Electrostatic damage to monitoring electronics during service
Symptoms
- Vehicle cannot be made ready
- Other drive faults stored at the same time, such as motor or isolation faults
Repair estimate
DifficultyShop_onlyWorkshop job
Parts and labour€300–8,000
Time2–10 h
Typical range across vehicles; the real cost depends on what the testing finds.
Parts involved
hvil loop phv connectors
Related codes
References: static.nhtsa.gov, law.cornell.edu.