03 5.7L slowing to a stop idle issue.

[MrFixIt]

Every time the truck is travelling more than 5mph and I depress the brake for 4-6seconds 'dash lightning bolt' lights up as the throttle reduces airflow and the engine begins to stall. Within 2 seconds of the lighting bolt the engine dies, unless the brake is released and depressed. The brake pedal must be pumped like this until the truck is at a complete stop, then the idle is fine and the stall situation is averted. So, what is happening seems to be the engine is attempting to use the transmission to help me slow the vehicle via deceleration. Should I need to corner in this 2 second timeframe, the power steering pump causes added power drain and will stall the engine abruptly and these trucks DON'T turn unless the power assist is available. Is there a

 

[Recoil]

Hmmm, when the lightning bolt comes on when the brake is depressed, does it go off when you take your foot off? If so, does it come back on immediately each time you press the brake when pumping the brakes to a stop?

 

[MrFixIt]

The lighting bolt comes on after about 5-6 seconds of braking during movement of the vehicle in either direction. If the brake is released or if the truck completely stops before the lightning bolt lights, normal operation is resumed. If the brake is released after the lightning bolt, then the lightning bolt goes out, and stays out, until the next 5-6 second braking with motion is done. The lightning bolt is now only coming on under that one condition. I'm thinking of placing a relay on the brake switch to open the circuit for 100msec when the brake pedal is actively lighting the brake lights. Also, the trailer/auxiliary brake unit can light the brake lights without causing any lightning bolt condition to exist.

Therefore, I believe this is happening in the PLC to assist deceleration of the vehicle after 5-6 seconds via the engine/transmission,. Compression braking, possibly???

Note the right front ABS/wheel motion indicator is throwing a fault and the ABS and brake lights are on all the time when the vehicle is running. I think it is a bad cable connection to the speed motion sensor in the hub that was replaced a couple months back.

 

[Recoil]

The ABS and brake light being on are probably nothing more than an annoyance, but just for the heck of it, see if you can resolve that issue to see if it makes any change in the stalling of the truck.