U3533 code meaning
High Voltage System Interlock Circuit K Low
Network system Generic code U35xx codes Check engine light
What U3533 means
U3533 says loop K reads too low. Apart from an open plug, part of the loop current may be escaping somewhere. Tesla's HVIL tech note for the Model S describes two such cases: a drive inverter whose control board leaked some of the nominal 20 mA loop current to ground, and a loop wire squeezed against ground close to a seat belt pretensioner. The fault therefore need not sit in a connector at all; a component on the loop or a wire trapped by seat or trim parts can cause it. When every plug of loop K is latched and the value stays low, measure the loop current at each component and inspect wiring near seat mounts. No maker documents U3533; the contactors remain open.
U3533 at a glance
- Check engine lightYes, usually on
- Emissions testNot an emissions code
- Limp modePossible
- Repair difficultyHard
- Typical labor0.5 to 5 hours
- Clears after repairWhen cleared with a scanner
Symptoms of U3533
- Vehicle does not reach ready mode
- Fault may follow work on seats or interior trim
- Warning to have the high-voltage system checked
Common causes of U3533
- Most likelyLoop K wire squeezed against ground by seat, trim or mounting parts
- PossiblePlug within loop K not connected
- Less likelyHigh-voltage component on loop K leaking loop current to ground internally
Check the most likely causes first. Replacing parts by guesswork is the most expensive way to clear a code.
Parts involved
Hvil loop kHvil wiring
What each part of U3533 means
| U | Network system: communication between the control modules (CAN bus). |
| 3 | Reserved range, usually generic. |
| 33 | The exact fault in that area. |
What to do next
- Note U3533 and any other codes stored with it: several codes together often point to one cause.
- Check for loose connectors and damaged wiring around the parts the code names.
- Check open recalls for your car: some faults are fixed for free by the dealer. Enter your VIN.
- Clear the code only after the repair. If it comes back, the fault is still there.
Buying a used car? Scan it for stored codes before you pay. A recently cleared memory can hide a problem.
Questions about U3533
What does U3533 mean?
U3533 means "High Voltage System Interlock Circuit K Low". U3533 says loop K reads too low. It is a generic code, so it means the same on every make.
Is it safe to drive with U3533?
Drive gently and only to a workshop. With U3533 the car can go into limp mode (reduced power) to protect itself.
Will U3533 fail an emissions test?
U3533 is not an emissions code, so on its own it usually does not fail an emissions test. Other stored codes or a lit check engine light still can.
How hard is U3533 to fix?
Difficulty: hard. A typical repair takes 0.5 to 5 hours of work. This is a job for a workshop.
Will U3533 clear itself after the repair?
Clear the code with a scanner after the repair. If the fault is fixed, it does not come back.