What are the common causes of U3538?

A short to voltage on interlock loop L. An open in interlock loop L. A loose interlock loop L connector. A failed interlock monitor inside the module.

Read high voltage interlock circuit L status on a scan tool. De-energize the high voltage system before touching any connector. Test interlock loop L for a short to voltage and opens. Inspect interlock loop L connector and wiring. Repair interlock loop L or replace the interlock module if the signal stays high. Clear the code and retest.

U3538

High Voltage System Interlock Circuit L High

System: Network communication (U code)
Lamp: Check Engine Light
Category: Network Communications

What it means

U3538 means High Voltage System Interlock Circuit L High.

Check these first

A short to voltage on interlock loop L
An open in interlock loop L
A loose interlock loop L connector
A failed interlock monitor inside the module

What to do next

Read high voltage interlock circuit L status on a scan tool
De-energize the high voltage system before touching any connector
Test interlock loop L for a short to voltage and opens
Inspect interlock loop L connector and wiring
Repair interlock loop L or replace the interlock module if the signal stays high
Clear the code and retest

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Updated

Generic SAE J2012 definition. Last updated 2026-10-10.