Hino Brake Switch Issue - Limited Power Acceleration

[Jordan]

Truck: 2012 Hino 268A
VIN: 5PVNJ8JV4C4S53377

Issue: Brake switch (I've already replaced, same issue - Plunger position/setting is also correct)
Symptoms: Truck is lagging from stop for almost exactly 15 seconds, then picks up and goes like it should, until brakes are applied again.

I can remove the brake switch and it runs as it should...this is true with the switch connected or disconnected, as long as the plunger isn't depressed on the brake switch. Once the plunger is depressed, it goes straight back to the lag, until I neutral out and then back into gear, or ride it out for the 15 seconds. I can hear and feel the relay clicking in the dash when the plunger is depressed as well. I just don't know where it goes from there. I can only assume, the computer thinks the brakes are still applied, because the symptoms are similar to that of an out of position plunger.

Dash: No codes (I currently don't own the proper Hino software, but considering I have 4 of these things, I should probably buy it soon).

I greatly appreciate any advice/direction you may be able to offer.

 

[Treadmill]

Truck: 2012 Hino 268A
VIN: 5PVNJ8JV4C4S53377

Issue: Brake switch (I've already replaced, same issue - Plunger position/setting is also correct)
Symptoms: Truck is lagging from stop for almost exactly 15 seconds, then picks up and goes like it should, until brakes are applied again.

I can remove the brake switch and it runs as it should...this is true with the switch connected or disconnected, as long as the plunger isn't depressed on the brake switch. Once the plunger is depressed, it goes straight back to the lag, until I neutral out and then back into gear, or ride it out for the 15 seconds. I can hear and feel the relay clicking in the dash when the plunger is depressed as well. I just don't know where it goes from there. I can only assume, the computer thinks the brakes are still applied, because the symptoms are similar to that of an out of position plunger.

Dash: No codes (I currently don't own the proper Hino software, but considering I have 4 of these things, I should probably buy it soon).

I greatly appreciate any advice/direction you may be able to offer.

Just check in periodically and our resident Hino mechanic will respond.

 

[Jordan]

Will do!

Thanks!

 

[Techmaster]

Assuming you have air brakes, Check the service air brake vavle switch at the rear axle. 2 wire harness going to the switch. Look for corroded wire or damaged pins. If the wires and pins are ok then unplug the switch, jump the two pins and go for a ride. Had a customer with those same symptoms and that was the problem. It will not set a code.

 

[Jordan]

Assuming you have air brakes, Check the service air brake vavle switch at the rear axle. 2 wire harness going to the switch. Look for corroded wire or damaged pins. If the wires and pins are ok then unplug the switch, jump the two pins and go for a ride. Had a customer with those same symptoms and that was the problem. It will not set a code.

I'll check this today, however, I also made an assumption that may be wrong:
- If I remove the brake pedal switch from the pedal housing and leave it hang, which wouldn't allow the switch to engage/disengage, I can run the truck like normal with no problems (except no brake lights, but the truck runs great). This is true if I leave the brake pedal switch connected and if I disconnect it. As long as the pedal switch isn't pushed, the truck does great.

Is the brake pedal switch at the pedal and the switch you mentioned at the back axle wired together? I guess I'll find out this morning when I try it. Do you have a better Idea of where the switch is at on the rear of the truck or where the wiring connects to for an easy locate?

Thanks,
Jordan

 

[Techmaster]

How did it go?

 

[Jordan]

Spot on! Fixed the original issue! Except there is now and ABS light that I can't get to go away.

There were a couple switches on valve on the rear of the crossmember which I disconnected first to check connections. I believe this caused the ABS light to come on, but I was messing with several connections at the same point, so I'm not sure.

At that point I noticed the harness just hanging on the front of the crossmember where the pins corroded/broke off in the harness itself. I got those pins out of the harness and robbed a switch/valve off another truck that was down for different reason, while waiting on parts. Our local Hino dealer doesn't seem to stock any parts, aside from brake shoes.

In other words, truck runs great, so thank you for your help and responses! If you have any suggestions on how to now get the ABS light off, that'd be great. I checked for dash codes, but there weren't any.

Thank you!

 

[Techmaster]

Glad I could help, retrace all the connection you messed with, possible u left something unplugged or not plugged in all the way, have it scanned to help you look.