My Lenovo IdeaPad 3 15ITL6 with an i5-1135G7 has been nearly unusable for about two years. The CPU frequently locks to a 4x multiplier, around 199 MHz, because BD PROCHOT is being triggered even when the processor is only 33–46°C. ThrottleStop shows BD PROCHOT active on the core, GPU, and ring, and the flag flickers on and off. If I disable BD PROCHOT, the laptop immediately returns to roughly 2.0–2.1 GHz and becomes usable again.
The issue happens on both battery and the original 65W charger. A full power reset and a BIOS update to GGCN61WW did not help, and the throttling returns shortly after a cold boot. Windows reports only 8.3% processor performance, but its own performance-limit flags do not show a normal Windows restriction. After sleep, the system can also drop to a 6W power limit and around 400 MHz until I restart it.
The cooling fan has become extremely quiet compared with how it used to sound. Under load, there is only a faint airflow from the rear vent and almost no warm air, so I suspect the fan may be clogged, failing, or not being controlled correctly.
I currently disable BD PROCHOT with ThrottleStop after every boot and avoid sleep. What should a repair shop test first? Could a weak fan, fan sensor, embedded-controller problem, motherboard power circuit, or another sensor be falsely asserting BD PROCHOT? Is it reasonably safe to leave BD PROCHOT disabled temporarily, and is there a safe fix for the 6W limit after sleep? I am also wondering whether updating the older Intel Dynamic Tuning driver would help.
2 Answers
The fact that disabling BD PROCHOT immediately restores normal speed strongly suggests that another device or controller is requesting emergency throttling. A bad fan or fan sensor is a reasonable first suspect, but it is not guaranteed to be the only one. Have the technician test fan RPM feedback and sensor readings rather than simply cleaning the vents.
Avoid treating the ThrottleStop setting as a permanent repair. Disabling BD PROCHOT can prevent legitimate protection from another overheating or power fault, so use it only briefly and monitor temperatures while arranging service. Do not stress the laptop heavily if the fan is not working. The sleep-related 6W limit may be an embedded-controller or Intel Dynamic Tuning state problem; updating the Lenovo-provided Dynamic Tuning and chipset drivers is worth trying, but it is unlikely to fix a physically failing fan or motherboard sensor. A full shutdown and restart is safer than repeatedly overriding the limit after sleep.
Start with the fan and cooling assembly. A fan that has become nearly silent and produces little airflow may be clogged, failing, disconnected, or not receiving the correct control signal. Ask the shop to open the laptop, clean the heatsink and vents, verify that the fan spins properly under load, inspect its connector, and replace the fan if its speed or airflow is poor. They should also check the thermal paste and confirm that the heatsink is seated correctly.
If the fan and heatsink are healthy, the next step is checking the embedded controller, fan tachometer signal, charger/power circuitry, and motherboard sensors. BD PROCHOT is an external emergency-throttling signal, so the CPU temperature alone does not prove that the CPU is the source.
If the fan is replaced or repaired, should BD PROCHOT stop activating automatically, or could the motherboard still be asserting it?