T1–T4 sensor replacement without draining the stack.

Before you begin, confirm the battery is isolated according to LOTO procedure 4-A and that the customer has been notified through the ticket. Record the start time in the service log so the SLA timer reflects on-site work.

Work through the steps in order. Each step is verifiable — do not continue past a step whose check fails; raise a blocking note on the ticket pinboard instead so the next technician has the context.

When the work is complete, capture the post-work telemetry snapshot, attach it to the ticket, and close the service log entry with the total time on site.