U353E: High Voltage System Interlock Circuit N Performance

What does U353E mean?

HVIL loop N timing/pattern does not match expected behavior. The interlock is a low-voltage signal loop routed through the HV connectors and covers; the monitoring module drives a current or signal through it and opens the HV contactors, or refuses to close them, when the loop is broken or out of range, so that no HV connection can be opened while live.

The code tells you which monitor failed, not which part is broken. Test before replacing parts.

Symptoms

• Vehicle will not switch to ready mode or the HV system shuts down
• High-voltage system warning in the instrument cluster
• Charging may be blocked

Common causes

• High Intermittent contact in HV connector
• Medium HV connector, service disconnect or cover switch not fully seated
• Medium Damaged interlock wiring or corroded terminal in the loop
• Low Fault in the module that drives and evaluates the interlock loop

Likelihood is a general estimate across vehicles; your make and model may differ.