257B parking brake seems intermittantly energized

[millerl]

When starting the machine, turning the key on all lights light up then when functioning normally parking light stay on and switch functions after starting. Last 30 hours when turning the key all lights light up then parking light goes out and switch won't function and engine starts but brake wont release hydraulics, checked all fuses, and it is sporadic, but has gotten worse, what do the ECM's do and could it be one of those. A wiring harness issue should be all or none ??? Any help appreciated!

 

[CrashWrench150]

Hi Miller, Can You Check For any " Trouble/ Falt Codes ??? I would Start with check / test The " Park brake switch " first . When you first turn the Igntion key " On " , but not started ,The " ECM" Is Checking all sensors , Then When the machine starts, It Does this "Checking " Again and Pump Charge Pressure . Check battery Connections - Ground cable , take apart the end going to the frame. Clean it . Now disconnect the ground off the battery, ( This is so you don't FRY the " ECM " )... In the Engine Compartment ( Facing the engine ) On the Left Side , Rear, Bottom corner is a Ground Braided Strap ( Take apart and clean ). next , Raise The Cab, To Access inside , !!!!! CAREFUL !!!!! CAB COULD FALL !!!!!!!!!!!!!!! Check All the ground cables on the underside of the Cab to Frame , ( I Mean, take Each one apart and Scrub them with a wire brush ). There Is a Wide braided ground Strap that connect the cab to the frame , Up by the rear cab pivot mounts . There is a Small braided Strap On one of the bolts that holds the " ECM "/Computer to the back wall of the Cab . Check the grounds Straps/ cables from the Engine To the Frame . Any kind of Rust or Corrowshion will screw up the " EcM" And Controls .... start With this and please Post what you find.. Good luck , One Step at A Time , Later, Mark K. High Point, N.C. USA

 

[kroog]

Hi Miller, Can You Check For any " Trouble/ Falt Codes ??? I would Start with check / test The " Park brake switch " first . When you first turn the Igntion key " On " , but not started ,The " ECM" Is Checking all sensors , Then When the machine starts, It Does this "Checking " Again and Pump Charge Pressure . Check battery Connections - Ground cable , take apart the end going to the frame. Clean it . Now disconnect the ground off the battery, ( This is so you don't FRY the " ECM " )... In the Engine Compartment ( Facing the engine ) On the Left Side , Rear, Bottom corner is a Ground Braided Strap ( Take apart and clean ). next , Raise The Cab, To Access inside , !!!!! CAREFUL !!!!! CAB COULD FALL !!!!!!!!!!!!!!! Check All the ground cables on the underside of the Cab to Frame , ( I Mean, take Each one apart and Scrub them with a wire brush ). There Is a Wide braided ground Strap that connect the cab to the frame , Up by the rear cab pivot mounts . There is a Small braided Strap On one of the bolts that holds the " ECM "/Computer to the back wall of the Cab . Check the grounds Straps/ cables from the Engine To the Frame . Any kind of Rust or Corrowshion will screw up the " EcM" And Controls .... start With this and please Post what you find.. Good luck , One Step at A Time , Later, Mark K. High Point, N.C. USA

It;s usually a harness or sensor problem and should show fault codes.