4WD connected to ABS - why? - GT-R Register - Official Nissan Skyline and GTR Owners Club forum

Pikey · 1st September 2006, 11:49 AM

Whenever you get the 4WD light on, the ABS light always comes on with it! Why is this?

I understand why pulling the fuse turns them both on - cos they're on the same fuse - but when you've got a fault with the 4WD system (G-sensors) like I have, why doesnt the ABS work? Seems very strange that two systems that shouldnt really be connected with one another should be knocked out together when there's a fault with one of them!

Toby Broom · 1st September 2006, 11:53 AM

doesn't the 4wd use the same wheel sensors to detect if the rears have lost grip an transfer power to front?

Pikey · 1st September 2006, 12:07 PM

That's part of it, yeah. But I dont have anything wrong with my ABS sensors, only the G-sensor unit which is nothing to do with the ABS system !

Zoltarc · 1st September 2006, 12:39 PM

R32 ATTESA computer also controls the ABS. For safety sake if a vital 4WD component fails the ECU will turn everything off.

Some smart ABS systems use 'G Sensors' to detect acceleration. This helps in the situation where you lock up every wheel, thus fooling the ECU into thinking the car is stationary (as the wheel speed is 0). If the ABS system references an accelerometer the rare situation where the ABS doesn't work under a full lock up is avoided.

However from memory the R32 ATTESA ECU doesn't use the G sensor for ABS operations.

Having said that I'm sure I've had my G sensors disconnected and the ABS light didn't come on...I may be suffering from clouded vision though :P

Toby Broom · 1st September 2006, 02:57 PM

I think they though that 20yrs down the line, there'd be some guy with a G sensor problem and they dissable everything to **** him off.

Pikey · 1st September 2006, 04:10 PM

I think that too

Rich C · 1st September 2006, 05:51 PM

The "ABS sensors" are actually wheel speed sensors, Atessa compares the individual wheel speed with the G sensors to work out if the car has lost grip and applies the neccessary power to correct the slide.

The GTR was one of the first cars in the world (maybe the) to apply this type of system and the two systems are directly linked, that's why pulling one fuse disables both systems.

An amazing system when you consider it was developed almost 20 yeas ago now! In my opinion modern traction control works in the completely wrong way - basically the same way but in reverse by removing excess power through ABS.

I think the R34 V-Spec II's may use both methods?

Rich C · 1st September 2006, 05:55 PM

Do you know it is definetely the G-sensors? HAve you checked with Consult / Diagnostics.

BTW I know the person that developed the G-sensor for the original GTR, i'll ask him why they did it like that..

Pikey · 2nd September 2006, 12:29 PM

Yeah definitely G-sensor. Ecu flashing codes 12 and 13, and the indicator on the front of the sensor unit has turned red

1st September 2006, 11:49 AM	#1 (permalink)
Pikey GTR Register Member Join Date: Feb 2004 Location: Cheltenham Posts: 4,151	4WD connected to ABS - why? Whenever you get the 4WD light on, the ABS light always comes on with it! Why is this? I understand why pulling the fuse turns them both on - cos they're on the same fuse - but when you've got a fault with the 4WD system (G-sensors) like I have, why doesnt the ABS work? Seems very strange that two systems that shouldnt really be connected with one another should be knocked out together when there's a fault with one of them!

1st September 2006, 05:51 PM	#7 (permalink)
Rich C GTR Register Member Join Date: Feb 2003 Location: Northampton Posts: 176	Atessa The "ABS sensors" are actually wheel speed sensors, Atessa compares the individual wheel speed with the G sensors to work out if the car has lost grip and applies the neccessary power to correct the slide. The GTR was one of the first cars in the world (maybe the) to apply this type of system and the two systems are directly linked, that's why pulling one fuse disables both systems. An amazing system when you consider it was developed almost 20 yeas ago now! In my opinion modern traction control works in the completely wrong way - basically the same way but in reverse by removing excess power through ABS. I think the R34 V-Spec II's may use both methods?

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1st September 2006, 11:53 AM	#2 (permalink)
Toby Broom New Users Join Date: Aug 2003 Location: Herts Posts: 1,481	doesn't the 4wd use the same wheel sensors to detect if the rears have lost grip an transfer power to front?

1st September 2006, 12:07 PM	#3 (permalink)
Pikey GTR Register Member Join Date: Feb 2004 Location: Cheltenham Posts: 4,151	That's part of it, yeah. But I dont have anything wrong with my ABS sensors, only the G-sensor unit which is nothing to do with the ABS system !

1st September 2006, 12:39 PM	#4 (permalink)
Zoltarc GTR Register Member Join Date: Jun 2005 Posts: 51	R32 ATTESA computer also controls the ABS. For safety sake if a vital 4WD component fails the ECU will turn everything off. Some smart ABS systems use 'G Sensors' to detect acceleration. This helps in the situation where you lock up every wheel, thus fooling the ECU into thinking the car is stationary (as the wheel speed is 0). If the ABS system references an accelerometer the rare situation where the ABS doesn't work under a full lock up is avoided. However from memory the R32 ATTESA ECU doesn't use the G sensor for ABS operations. Having said that I'm sure I've had my G sensors disconnected and the ABS light didn't come on...I may be suffering from clouded vision though :P

1st September 2006, 02:57 PM	#5 (permalink)
Toby Broom New Users Join Date: Aug 2003 Location: Herts Posts: 1,481	I think they though that 20yrs down the line, there'd be some guy with a G sensor problem and they dissable everything to **** him off.

1st September 2006, 04:10 PM	#6 (permalink)
Pikey GTR Register Member Join Date: Feb 2004 Location: Cheltenham Posts: 4,151	I think that too

1st September 2006, 05:55 PM	#8 (permalink)
Rich C GTR Register Member Join Date: Feb 2003 Location: Northampton Posts: 176	Do you know it is definetely the G-sensors? HAve you checked with Consult / Diagnostics. BTW I know the person that developed the G-sensor for the original GTR, i'll ask him why they did it like that..

2nd September 2006, 12:29 PM	#9 (permalink)
Pikey GTR Register Member Join Date: Feb 2004 Location: Cheltenham Posts: 4,151	Yeah definitely G-sensor. Ecu flashing codes 12 and 13, and the indicator on the front of the sensor unit has turned red