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U3526 — High Voltage System Interlock Circuit G Performance

Manufacturer-specificNetwork / communication

The U3526 code indicates a performance issue within the High Voltage System Interlock (HVIS) circuit G. This low-voltage safety loop monitors the integrity of high-voltage component connections to ensure the system is safely sealed before enabling power.

Symptoms

What causes it — most likely first

1. Loose or poorly seated connector

A high-voltage component connector may not be fully locked, breaking the low-voltage interlock loop.

2. Corroded interlock terminals

Moisture or debris in the interlock pins can create high resistance or intermittent continuity.

3. Damaged interlock wiring

Frayed, pinched, or rodent-damaged low-voltage wires within the interlock circuit.

4. Internal component failure

A failure of an internal switch or sensor within a high-voltage component (e.g., inverter or charger).

5. Hybrid Control Module fault

The module monitoring the interlock loop may have an internal circuit failure.

6. PCM/ECM failure

A failure in the main engine computer's processing of the interlock signal, though this is rare.

How it's diagnosed

  1. Perform a visual inspection of all high-voltage connectors to ensure they are fully seated and locked.
  2. Inspect the interlock wiring harnesses for signs of chafing, shorts, or physical damage.
  3. Use a digital multimeter to check for continuity across the interlock loop components.
  4. Check for corrosion or moisture ingress within the interlock plugs.
  5. Perform a voltage drop test on the interlock circuit to identify high-resistance points.
  6. Clear the code and attempt a system restart to verify if the fault is intermittent.

Code facts & related codes

SystemNetwork / communication
StandardizationManufacturer-specific (P1/B1/C1/U1)
Related codesU3520 — High Voltage System Interlock Circuit U3521 — High Voltage System Interlock Circuit U3522 — High Voltage System Interlock Circuit U3523 — High Voltage System Interlock Circuit U3524 — High Voltage System Interlock Circuit U3525 — High Voltage System Interlock Circuit

Frequently asked

Is it safe to drive with a U3526 code?

Generally, no. This code often triggers a safety shutdown of the high-voltage system, which will prevent the vehicle from moving.

Does this mean my high-voltage battery is defective?

Not necessarily. The interlock circuit is a low-voltage safety loop; the battery itself may be healthy, but the connection monitoring it is compromised.

Should I replace the PCM/ECM to fix this issue?

No. This code is almost always caused by a physical connection, wiring issue, or a failed component within the interlock loop rather than the computer.