Front brakes locked up

[Headnsouth]

2005 G35 Sedan base
Both front calipers will apply pressure but they won't release. Tried to compress with a C clamp and still NG unless I opened the bleed screw. Compressed both pistons and reassembled. Still have the same issue.
What's next?

[Headnsouth]

Is it possible that both calipers locked up at the same time or could it be something else in the system causing the lock up issue?

[VStar650CL]

The ABS system on your G is set up dual-diagonal, with the back side of the Master driving LF/RR and the front side driving RF/LR. See BRC-7 here:
https://www.nicoclub.com/service-manual ... %2Fbrc.pdf

The FSM doesn't show any external metering valve. There probably is a metering orifice setup inside the ABS, but that will be a differential orifice size and can't cause a lockup. So for both circuits to lock up, it's very unlikely anything except the Master or a misadjusted brake pedal is causing the issue.

[Headnsouth]

Thanks for your reply. I was hoping it would be something simple. Blah.
Guess I've got a bit of reading to do. Thanks for the link to the FSM.

[Headnsouth]

I loaned out a innova 3130 and it only gave me code C0291.
ESP control unit is incomplete.
Any idea what that means?
It's for something to do with stability control but that's about all I can find about the code.

I had all 4 wheels off of the ground and tried to turn the wheels. Locked up.
Cracked open the lines on the MC and that freed up the wheels.
No dash lights referring to abs or traction control.

[VStar650CL]

If cracking the lines at the master freed them up then the problem is in the master or the brake pedal adjustment, not the ABS or anything downstream. I just checked the FSM and your ABS is only designed to talk to the Consult2, not a regular CAN or K-line link. The codes it outputs are proprietary and only a C2 or C3+ will know what they mean.

[Headnsouth]

Got a new MC on order. Hopefully that'll take care of it.
As far as brake pedal adjustment, what is there to adjust? It's never been touched.
I did adjust the rear E brake but that's all.

[VStar650CL]

As far as brake pedal adjustment, what is there to adjust? It's never been touched.
I did adjust the rear E brake but that's all.

True then, but make sure the pedal switch didn't stick and isn't holding the pedal slightly. That's usually a Sentra issue, but worth taking a look.

[Headnsouth]

New MC and the brakes are crap. Can't seem to build up consistent pressure. I've ran a quart of BF through the system and the pedal is mush. Disconnected the neg terminal on battery and bled, no difference. Not much force or quantity of BF when I bleed either.

I just checked the FSM and your ABS is only designed to talk to the Consult2, not a regular CAN or K-line link. The codes it outputs are proprietary and only a C2 or C3+ will know what they mean.
Top

These are scan tools that'll be able to check for ABS issues on my vehicle? Any scan tool you would recommend?

[VStar650CL]

New MC and the brakes are crap. Can't seem to build up consistent pressure. I've ran a quart of BF through the system and the pedal is mush. Disconnected the neg terminal on battery and bled, no difference. Not much force or quantity of BF when I bleed either.

I just checked the FSM and your ABS is only designed to talk to the Consult2, not a regular CAN or K-line link. The codes it outputs are proprietary and only a C2 or C3+ will know what they mean.
Top

These are scan tools that'll be able to check for ABS issues on my vehicle? Any scan tool you would recommend?

How are you bleeding it? It needs to be done top-down, first the Master at both fittings, then the ABS at the entry fittings, then the four ABS exit fittings, then the wheels. Air caught high up in the system often won't push out just by bleeding the wheels, it percolates back up the lines.

I honestly don't know about a scanner, we have a working C2 at the shop and I'd be using that. All I can gather is that the codes are Nissan-proprietary, so the FSM isn't helpful and it's likely only something very high-end will be able to translate them into CAN-speak.

[Headnsouth]

New MC and the brakes are crap. Can't seem to build up consistent pressure. I've ran a quart of BF through the system and the pedal is mush. Disconnected the neg terminal on battery and bled, no difference. Not much force or quantity of BF when I bleed either.


These are scan tools that'll be able to check for ABS issues on my vehicle? Any scan tool you would recommend?

How are you bleeding it? It needs to be done top-down, first the Master at both fittings, then the ABS at the entry fittings, then the four ABS exit fittings, then the wheels. Air caught high up in the system often won't push out just by bleeding the wheels, it percolates back up the lines.

I honestly don't know about a scanner, we have a working C2 at the shop and I'd be using that. All I can gather is that the codes are Nissan-proprietary, so the FSM isn't helpful and it's likely only something very high-end will be able to translate them into CAN-speak.

I hadn't read about all of those different bleed points but it makes sense. I'll give it a shot. Thx