2005 xc 90 front passenger brake locked up

[Krons]

Does anyone know the fuse for ABS circuit?
I am thinking about pulling the fuse...

No ABS feature is still better than random wheel locking up!

I don’t know where the fuse is (best option) but do know if you disconnect the passenger wheel speed sensor right in front of the passenger windshield cowl it’ll disable the ABS.

[cn90]

Thanks for the info.

I am reading up on the functionality of the ABS system.
If I understand correctly, then the ABS system only reduces the braking effect and NOT applying braking effect.

So, let's say it detects the RF wheel slipping on ice, it REDUCES hydraulic pressure to the RF caliper so the wheel does NOT lock up.

I don't think the ABS system ever applies the brake? I might be wrong though...

[abscate]

Thanks for the info.

I am reading up on the functionality of the ABS system.
If I understand correctly, then the ABS system only reduces the braking effect and NOT applying braking effect.

So, let's say it detects the RF wheel slipping on ice, it REDUCES hydraulic pressure to the RF caliper so the wheel does NOT lock up.

I don't think the ABS system ever applies the brake? I might be wrong though...

It does with the TRACS or STC system engaged to stop wheel slip. If you have a STC button maybe try turning it off

[ggleavitt]

See attached, detailed function specific.

ABS XC90 2005.pdf

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Per VIDA:
While driving, the brake control module (BCM) (1) registers the acceleration and deceleration of the wheels. The 4 wheel sensors (3) (one on each wheel) give the brake control module (BCM) information about the rotation speed of the wheels. The brake control module (BCM) calculates the speed of the car using this information and puts it out on the Control area network (CAN). There the signal is accessible for other systems.

During braking, the brake control module (BCM) receives a signal from the brake lamp switch (2) indicating braking. The brake control module (BCM) then goes into standby mode for ABS control. The signal from the brake lamp switch is not required for ABS control, but does give softer control at the beginning of ABS control.
If the brake control module (BCM) detects that there is a risk of wheel lock-up, the ABS hydraulic modulator (4) is affected and the hydraulic pressure for the relevant wheel is adapted so that wheel lock up is avoided.

The pressure in the circuit is controlled so that the maximum possible braking force is transferred to the road surface. This occurs when the wheel rotates with 12-20% slippage on the surface.

ABS is first activated when the speed of the car exceeds approximately 7 km/h, which means that at speeds below approximately 7 km/h the wheels can lock up. This has no practical effect on the function of the system or from the driver's point of view.

ABS control can be divided into three stages:

1.Open position. (Pressure increase). This is the normal condition during braking. The inlet valve is open and the outlet valve is closed. This permits the brake pressure to pass from the master cylinder to the wheel

2.Pressure retention phase. (Constant pressure). If the brake control module (BCM) detects that one of the wheels is rotating too slowly, the brake control module (BCM) will close the inlet valve. This stops the brake pressure to the wheel from increasing, even if the driver increases the pressure on the brake pedal. If the rotation speed of the wheel continues to fall the control moves into the pressure reduction phase

3.Pressure reduction phase. (Pressure release). The inlet valve remains closed. The brake control module (BCM) opens the outlet valve and starts the pump which transfers brake fluid from the wheel, this reduces the brake pressure. When the rotation speed has increased sufficiently the control module closes the exhaust valve, opens the inlet valve and control returns to the open position.

Steps 1, 2 or 3 are repeated until braking finishes or the ABS system stops.

[cn90]

This is 2005 XC90 2.5T fusebox lid, ABS fuses are #1 and #2...

PS: later years have a different fusebox numbering system.

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[cn90]

Thanks ggleavitt!

So it is the "failure to release the pressure control valve" that can cause wheel lock up!

PS: my saga happened during a good day with temp at 10C, no snow nothing. Road was perfect. Just made a right turn into a shopping mall at 15-20 km/h, then RF wheel locked up. Then later released as mentioned above.

[ggleavitt]

Last 6 of your VIN (chassis)?

I'm looking at both 2004 and 2005 EWD and don't see this fuse match. Apologies for the bother, want to provide you with accurate information.

[abscate]

Canbus transitioned on p2 cars between 2004 and 2005 so it’s a cinch you will have to match model year for that fuse info.

[ggleavitt]

I'm very aware of the transition, see attached for what else changes with MY05, it's not just CANBus.

MY2005 Technical presentation A4.pdf

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2005 EWD does not have the BCM 1 and 2 fuse allocation, 2006 onward does. Why I'm asking about chassis number, the title of thread is 2005.