P2D59: Generator B Over Temperature

What it means

Generator B reports temperature above the protection threshold. Sustained high load or cooling path obstruction.

At a glance

• Usually lights the check-engine light
• The engine or gearbox may go into limp mode

How it works

Generator B produces electrical power and has a temperature monitored by the hybrid control system. This code sets when Generator B exceeds its protection temperature, so the vehicle may reduce generator load or limit charging and electric-drive operation.

Common causes

Most likely first.

1. Sustained high generator load
2. Cooling path blocked

Symptoms

• Check-engine or hybrid-system warning
• Reduced power or electric-drive performance
• Charging or hybrid operation may be limited

How to diagnose it

1. Use freeze-frame data to see the temperature, load, and vehicle conditions when Generator B overheated.
2. Check live Generator B temperature and compare it with other available temperatures and the manufacturer's allowed range.
3. Inspect the Generator B cooling path for blocked airflow or coolant-flow obstruction, following high-voltage safety procedures.
4. Check for related cooling-system, inverter, or generator codes and verify that the cooling system operates as specified.
5. If cooling and load conditions are normal, test the temperature sensing circuit and Generator B for an internal heat source.

Common fixes

• Remove an identified obstruction from Generator B's cooling path.
• Restore a faulty cooling flow or airflow component identified by testing.
• Repair the Generator B temperature sensor circuit if it is giving an incorrect reading.
• Repair Generator B if it continues to overheat despite correct cooling and valid temperature data.

Can I keep driving?

Stop and let the vehicle cool if a temperature warning or reduced power occurs, and avoid towing, steep climbs, or repeated hard acceleration. Continued overheating can cause the system to restrict operation and may damage Generator B.