I know greasytshirt has discussed this problem Ad nauseam... but I have had no luck with the fixes, I have already checked the brake switch and the other adjustable switch on the brake pedal and both are functioning normally. My situation has a little quirk to it, in that, my hydra-boost pump runs continuously in the Key On-Engine Off position. And it stops as soon as I start the truck. Could there be a relay in the system that is having some affect on the circuit, as to make it think the brake pedal is pushed? As I remember, the pump normally only runs when you are pressing the brake pedal.
07 Hino 145 No Acceleration from idle to 1500+ RPM
- Thread starter intrmtn
- Start date
The hydroboost function you're describing is normal. That motor is running any time the key is on and it's not running.
At this point access to some diagnostic software might be necessary.
At this point access to some diagnostic software might be necessary.
Hi greasytshirt,
Thanks for the reply... I am not familiar with any of the diagnostic equipment required for these trucks, I see they have two interface connections, a standard OBDII connection and then what looks like a 9- pin as well. I have OBD scanners, but they don't seem to want to talk to this system. Can you direct me to what might be needed?
Additionally, I am quite sure that, up until today, the Hydraboost did not actually run when in the Key On/ Engine Off position unless you had your foot on the brake pedal. Otherwise, the motor would be running all the time you have the key on for any reason. I know the system is intended to make pressure in the event the truck dies or you lose steering system pressure. That is why I thought there might be some interaction with regard to this.
Thanks for the reply... I am not familiar with any of the diagnostic equipment required for these trucks, I see they have two interface connections, a standard OBDII connection and then what looks like a 9- pin as well. I have OBD scanners, but they don't seem to want to talk to this system. Can you direct me to what might be needed?
Additionally, I am quite sure that, up until today, the Hydraboost did not actually run when in the Key On/ Engine Off position unless you had your foot on the brake pedal. Otherwise, the motor would be running all the time you have the key on for any reason. I know the system is intended to make pressure in the event the truck dies or you lose steering system pressure. That is why I thought there might be some interaction with regard to this.
If the system if functioning correctly. The pump motor should run constantly anytime the key is on and the engine is off. The 9 pin is for Meritor Walcott brakes & Allison transmissions. The 16 pin is for the engine. Hino 16p are different from Mack/Volvo 16p. That may be why you can’t communicate. And even if you could generic scanners are pretty much useless on Hinos. I would recommend dealer software if you are serious about diagnostic capabilities