Network, generic (extended)

U3535 High Voltage System Interlock Circuit L

Check engine lightOn
EmissionsNot relevant
Drive cycleNot required
Limp modePossible

U3535 is the umbrella code for interlock circuit L, the eleventh loop. Large vehicles carry many guarded compartments. On New Flyer battery buses the energy storage units sit on the roof at front, centre and rear, and each access door is watched by an interlock limit switch. A service instruction from the bus maker, filed with NHTSA, swaps the switch bracket for one with a stop and bonds a striker plate to the door so the switch is pressed reliably; the same procedure turns a separate HV interlock switch off for lockout. A misadjusted door switch, or a lockout switch not turned back on, can open a loop such as L. Which compartments belong to it is not published.

Likely causes

Door or lid limit switch on loop L misadjusted or not actuated
Manual high-voltage interlock or lockout switch left off after service
Connector in loop L not fully latched
Controller monitoring loop L faulty

Symptoms

  • Vehicle or one energy storage unit unavailable after maintenance
  • High-voltage system warning on the dashboard
  • Fault linked to opening or closing a compartment

Repair estimate

DifficultyHardWorkshop job
Parts and labour€60–1,500
Time0.5–4 h

Typical range across vehicles; the real cost depends on what the testing finds.

Parts involved

hvil loop lhv connectors

Related codes

U3536U3537U3538U3531P0A0A

References: static.nhtsa.gov, law.cornell.edu.