Dash Brake Light on/off

My 92 k2500 dash brake light comes on with acceleration and right or left turn and sometimes goes off later. The code is a 9 which is the speed sensor
code. However, on this model that is also the default code. The speedometer still works so that indicates the sensor from the transfer case is OK. The speed signal is split three ways by the buffer. Is there a way to test the buffer short of replacement with known good unit? How is the speed of the wheels compared to the speed sensor to cause the RWAL unit to pulse the brakes? Thanks in advance for any feedback?
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Do you know for sure it's just not the switch on the emergency brake? Try wiggling it while you watch the brake light.
Al
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When it is on and I push on the emergency brake the indicator brightens. I read that there are three levels of brightness; 1. Emergency Brake. 2. RWAL brake malfunction and 3. Brake fluid problem. Since the light brightens with the emergency brake and there isn't a performance issue with braking I'm focused on the RWAL system.
Thanks for the input as I do tend to make things harder than need be.

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