How-to: ABS/EBD Live On/Off Switch - Second Generation Nissan Xterra Forums (2005+)
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post #1 of 3 (permalink) Old 12-03-2018, 09:26 PM Thread Starter
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How-to: ABS/EBD Live On/Off Switch

I finally had time to work on a new ABS/VDC/TCS/EBD off switch mod and while I was only trying to get the ABS to turn off (the version 3 abs-off yaw sensor disable thread didn't work for me) the results ended up being worthy of a new thread. When everything was back together and I was testing the mod I found that if I turned the rocker switch on, the ABS/BRAKE/SLIP/VDC lights all came on and were disabled. I'm thinking ok great, that's what I wanted. But with the truck still running I flipped the rocker switch off and both the ABS and Brake lights turned off. I was like wait a second and flipped the switch back on, both the ABS/BRAKE lights turned on again. Then I flipped the switch off again and the ABS/BRAKE lights both turned off again. This mod gives you the ability to turn the Anti Lock Brakes and Electronic Brake Distribution on/off just by flipping a rocker switch, no truck restart required. I should also note that at least for now you will still have to restart to re-enable the VDC and TCS although I plan on getting rid of that requirement in a future update. For the mod you'll need:


  1. Rocker Switch
  2. Bosch style relay
  3. Primary wire
  4. electrical connectors
  5. Wire stripper
  6. Zip ties/splicing tape, etc.





Section 1: Systems Background Info

It helps to be familiar with the systems on the X so to start I'm going to talk about the different systems the X has and what they do so you'll have a reference guide for the terminology used and get a better idea of what what you're dealing with. The Xterra has multiple electronic driving aid systems, some trim levels may have additional systems like Hill Start (HSA) and Hill Descent Assist (HDC). But everyone should have Anti Lock Brakes (ABS), Electronic Brake Distribution (EBD), Traction Control (SLIP), and Vehicle Dynamic Control (VDC). Here's a look into what those systems do:
ABS
● The Anti-Lock Brake System detects wheel revolution while braking and improves handling stability during sudden braking by electrically preventing wheel lockup. Maneuverability is also improved for avoiding obstacles.
● If the electrical system malfunctions, the Fail-Safe function is activated, the ABS becomes inoperative and the ABS warning lamp turns on.
● The electrical system can be diagnosed using CONSULT-II.
● During ABS operation, the brake pedal may vibrate lightly and a mechanical noise may be heard. This is normal.
● Just after starting the vehicle, the brake pedal may vibrate or a motor operating noise may be heard from engine compartment. This is a normal status of operation check.
● Stopping distance may be longer than that of vehicles without ABS when vehicle drives on rough, gravel,or snow-covered (fresh, deep snow) roads.



EBD
● Electronic Brake Distribution is a function that detects subtle slippages between the front and rear wheels during braking, and it improves handling stability by electronically controlling the brake fluid pressure which results in reduced rear wheel slippage.
● If the electrical system malfunctions, the Fail-Safe function is activated, the EBD and ABS become inoperative, and the ABS warning lamp and brake warning lamp are turned on.
● The electrical system can be diagnosed using CONSULT-II.
● During EBD operation, the brake pedal may vibrate lightly and a mechanical noise may be heard. This is normal.
● Just after starting the vehicle, the brake pedal may vibrate or a motor operating noise may be heard from engine compartment. This is a normal status of operation check.



TCS
● Spinning of the drive wheels is detected by the ABS actuator and electric unit (control unit) using inputs from the wheel speed sensors. If wheel spin occurs, the drive wheel right and left brake fluid pressure control and engine fuel cut are activated while the throttle value is restricted to reduce the engine torque and decrease the amount of wheel spin. In addition, the throttle opening is controlled to achieve the optimum engine torque.
● Depending on road condition, the vehicle may have a sluggish feel. This is normal, because optimum traction has the highest priority during TCS operation.
● TCS may be activated during sudden vehicle acceleration, wide open throttle acceleration, sudden transmission shifts or when the vehicle is driven on a road with a varying surface friction coefficient.
● The SLIP indicator lamp flashes to inform the driver of TCS operation.



VDC
● In addition to the ABS/TCS function, the driver steering amount and brake operation amount are detected from the steering angle sensor and pressure sensors, and the vehicle's driving status (amount of understeering/over steering) is determined using inputs from the yaw rate sensor/side G sensor, wheel speed sensors, etc. and this information is used to improve vehicle stability by controlling the braking and engine torque application to the wheels.
● The SLIP indicator lamp flashes to inform the driver of VDC operation.
● During VDC operation, the vehicle body and brake pedal may vibrate lightly and a mechanical noise may be heard. This is normal.
● The ABS warning lamp, VDC OFF indicator lamp and SLIP indicator lamp may turn on when the vehicle is subject to strong shaking or large vibration, such as when the vehicle is on a turntable or a ship while the engine is running or on a steep slope. In this case, restart the engine on a normal road and if the ABS warning lamp, VDC OFF indicator lamp and SLIP indicator lamp turn off, there is no problem.



HDC
● The hill descent control system will help maintain vehicle speed when driving under 25-35 km/h (15-21 MPH) on steeper downhill grades. HDC will provide braking allowing the driver to concentrate on steering while reducing the burden of brake and accelerator operation.
● To operate the system, set the 4WD switch to 4H or 4 LO and push the HDC switch. The HDC indicator in the combination meter will turn on. While HDC is operating, the stop/tail lamps will illuminate.
● If the accelerator or brake pedal is depressed while the HDC system is on, the system will stop operating.
● During HDC operation, a mechanical noise may be heard. This is normal.



HSA
● The HSA system will assist the driver by applying the brake automatically and preventing the vehicle from rolling backward when starting on an uphill.
● The maximum holding time is 2 seconds. After 2 seconds, the vehicle will begin to roll back gradually and then HSA will stop operating completely.

Fail Safe Modes
There are two fail safe mode that can be activated. You can tell which one has been activated by the dash lights illuminated:
1. In case of an electrical malfunction with the ABS, the ABS warning lamp, VDC OFF indicator lamp and SLIP indicator lamp will turn on.
2. In case of an electrical malfunction with the EBD system, the BRAKE warning lamp, ABS warning lamp, VDC OFF indicator lamp and SLIP indicator lamp will turn on.

Once Fail-Safe Mode has been activated certain dash lights will illuminate. You can tell what has been disabled by what lights are on, for example if SLIP/VDC are illuminated that means traction control and stability control are off but the anti lock brakes and electronic brake distribution are still on. Here are the results of fail-safe mode on the different systems:

ABS/EBD Fail-Safe Modes
1. For ABS malfunction, only the EBD is operative and the condition of the vehicle is the same condition of vehicles without ABS/TCS/VDC system.
2. For EBD malfunction, the EBD and ABS become inoperative, and the condition of the vehicle is the same as the condition of vehicles without ABS/TCS/VDC or EBD system.

HDC/HSA Fail-Safe Modes
● In case of HDC system malfunction, the HDC indicator lamp will remain off even though the HDC switch is operated and the condition of the vehicle is the same as the condition of vehicles without HDC system.
● In case of HSA system malfunction, the VDC OFF and SLIP indicator lamps are turned on and the condition of the vehicle is the same as the condition of vehicles without HSA system.

VDC/TCS Fail-Safe Modes
In case of TCS/VDC system malfunction, the VDC OFF indicator lamp and SLIP indicator lamp are turned on and the condition of the vehicle is the same as the condition of vehicles without TCS/VDC system. In case of an electrical malfunction with the TCS/VDC system, the ABS control continues to operate normally without TCS/VDC control.






Section 2: System Layout

The way the system is set up the abs brain under the hood receives a variety of date from the wheels, steering, etc that it uses to make decisions. For the mod we need to disrupt that data flow to trick the system into a Fail-Safe mode. After reading through the FSM I decided to to focus on the brake signal input. The system canít activate if it doesnít know when the brakes are being applied and it seemed like one of the less complicated systems to mess with. Here are a few diagrams of the wiring layout and the harnesses on both the brake side and the abs brain side:






Section 3: The Mod

So now to the good stuff, the actual mod. I followed the instructions in the ABS off Version 3 mod for the configuration of my rocker switch. The switch has a 12v input, a ground, and a power out (the part of the switch that sends power). The power out runs to a single relay, hereís a couple sketches of my wiring setup. Disregard the notes about the Yaw sensor:




Just like in Phulld's version 3 mod this switch and relay combo is set up to disrupt the connection of a wire. With the switch off, the system functions normally, with it on the connection is broken, the abs brain senses something wrong and puts the system in fail-safe. However unlike in the version 3 mod we donít touch the Yaw Sensor wiring and instead go straight to the abs brain.

Open the hood and locate the abs controller harness, itís near the driver side firewall. The harness itself has one latch that has to be pulled to release the harness. Be careful with it the tracks get full of dirt and dust and donít like to slide easily (at least on an 06). With that disconnected use a small pair of scissors or a knife to cut away at the wrapping on the wire bundle but make sure not to knick any of the wires.


Locate the sky blue wire with the silver dash marks. Thatís the brakes Ďoní input wire.



I made sure I had sufficient slack to attach connectors and then snipped the wire, reconnected the harness and turned the truck on to test. All of the right dash lights were on so went back and connected a wire to each end of the wire I cut. Then I ran those wires back through the firewall and to my relay. The wire end going into the abs brain goes on connector 87a and the end coming from the truck goes to connector 30. The way it works is you flip the rocker switch, it sends power to the relay and connector 30 is switched to connector 87. Given we donít connect anything to 87 the signal becomes a dead end. Make sure you secure all of the wires you ran and re-wrap the abs wiring harness so you keep everything protected. I used some weatherproof splicing tape I bought at Ace Hardware:


And thatís it! Remember this mod is no restart required to re-enable the ABS and Brake Distribution but to reactivate the VDC/SLIP you will need to restart. Iím working that one out now, my goal is to get rid of the restart completely. Happy modding!



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Last edited by General_Tarfun; 12-11-2018 at 02:02 PM.
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post #2 of 3 (permalink) Old 12-04-2018, 02:21 PM
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Thanks for this. Will try this week.
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post #3 of 3 (permalink) Old 01-31-2019, 11:21 AM
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Extremely informative. Thank you!
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