SW17LS

Forgive me if I'm being stupid...but isn't the PCS...the PRE COLLISION SYSTEM only activated when a collision is unavoidable?

Here's a description of the feature from Lexus.com:

So...you would not experience the system working unless you were in a situation where a frontal collision was imminent. Just because you can't "make the system work", doesn't mean it doesn't work.

williakz

There is massive confusion between PCS and Advanced PCS (APCS). The PCS simply preps various systems for the possible collision it thinks is coming. The APCS actively attempts to avoid the collision by alerting the driver and, if no adequate response is detected, by actually braking the vehicle. In my mind PASSIVE and ACTIVE would be better descriptors, but some people think PASSIVE means the driver doesn't have to do anything (ie. APCS) whereas ACTIVE is where the driver must get involved (ie. PCS). Thus the confusion continues...

SW17LS

Which product does the GS have? Seems to be PCS...

hziemba

Determining just what PCS or APCS do is not as easy as it might seem, and finding contradictory information is par for the course.

PCS was available in the 06 GS and every indication was that its only objective was to reduce the severity of a collision (in addition to the obvious radar cruise control). It got confusing when they came out with the driver attention monitor that looked for your face to determine if you weren't looking where you were going and to give you an earlier warning if that was the case. This was added to the PCS capability in the LS - I forget which year that was - and they referred to it as the Advanced PCS (APCS).

When the new GS came out, that APCS (or what it seemed to be) went into it.
When the new LS came out, they added the cameras near the rearview mirror into the system, and that became APCS. The GS system seemed to be referred to as PCS, and the ES system also was referred to as PCS, even though it doesn't have the driver attention monitor.

In reviewing the owner manual, the service manual, and other Lexus info, there's no doubt that the GS system is supposed to provide a warning before the collision is imminent (I believe the term they use is likelihood, but I'll have to check )...the big unanswered question is just how much warning. Even worse, they chose not to offer a sensitivity adjustment.

Regardless of which brand you buy, all these collision prediction systems are described with a certain vagueness, and a lot of "weasel words" put in by lawyers. I can understand the need for caveats, but I'm sure there's a lot more they could tell us. What makes it worse is that you can't find a demo car with this system, so you're really ordering it with a certain touch of faith.

I wouldn't consider buying a car without it, but I must say I'm disappointed, especially when I see what other brands, like Volvo, have out there. I thought of Lexus as a leader, not a "leader from behind".

DaveGS4

iTrader: (2)

PCS activation should be easily noticed by the driver because the seat belts automatically tighten down to pull you close into the seat. It's pretty dramatic (at least on my LS).

hziemba

Have you personally experienced it? Can you elaborate on the circumstances around the activation? How much warning did you get?

What model year are you talking about?

hziemba

Just a couple of clips from the 2013 GS350 service manual:

1. OUTLINE
(a) Pre-collision System (PCS)
(1) The pre-collision system predicts the possible collision of the vehicle with an obstacle, based on information received from various sensors. The obstacle may be a vehicle traveling in the opposite direction. PCS lessens the damage sustained in the collision by working in unison with other systems to optimize the characteristics of the occupant protection devices such as the seat belt retraction mechanism, and systems that dampen the impact of a collision, such as the brake control system.
(2) This system uses a millimeter wave radar sensor assembly to predict a possible collision with a vehicle or obstacle in front. The system retracts the seat belts before the collision and performs brake assist control and brake control.
(3) When the system determines that there is a possibility of a collision, and it judges that the driver is not facing forward or eyelids are not open based on information from the driver monitor camera, pre-collision warnings are provided in advance to warn the driver. If the driver continues facing away from the road, the brakes will be applied briefly to provide a sensory warning to the driver (pre-collision alert braking).

4. FUNCTION
(a) Warning Messages Displayed in Combination Meter Assembly
(1) The combination meter assembly uses the master warning light, PCS warning light, multi buzzer and multi-information display to provide the driver with pre-collision system warnings and indications.
(2) If the driving support ECU assembly determines that there is a possibility of a collision, it sends a signal to the combination meter assembly. Upon receiving this signal, the combination meter assembly indicates a warning on the multi-information display, master warning light and PCS warning light. Details are indicated below.
(3) If the driving support ECU assembly determines that the possibility of a collision is high, it sends a signal to the combination meter assembly. Upon receiving this signal, the combination meter gives a warning using the multi-information display, master warning light and PCS warning light, and sounds the skid control buzzer assembly. Details are indicated below:

DaveGS4

iTrader: (2)

I have experienced it in my LS (a 2005 LS430 Ultra) so it isn't the same system. It's gone off three times since I've had the car (twice with me in it) and all three times it was warranted where the car was closing very quickly on another stopped vehicle and entering a situation where there should have been full braking and maneuvering.

The first time it went off my wife was driving in the very early morning to the gym (still dark) on a 55 mph road and a car had broken down with no lights on in the middle of a lane. She came up on it at speed and PCS went off as she swerved around it, closely missing. I've had it activate when I was driving in highway traffic and the car at some distance in front of me put on brakes and as I realized they had come to a full stop (closing much too rapidly) and started braking at full pedal it went off.

The belt tightening is very noticeable, it pulls you back into the seat very tight to best prepare for a potential crash. After the event is over it loosens up again. You get notice on the dashboard and audible warning. I could tell a difference in braking boost as well once it activated.

Just curious since the OP never mentioned the belts tightening if his PCS went off or something else happened.

sydtoosic

i am here to say it was not the PCS that caused SNiiP3R to stop suddenly while changing lanes. it happened to me today on the Belt Parkway. my PCS was not engaged... it was turned off. i was changing lanes because the car in front of me (in the left lane) was moving at a snails pace with no one in front of him/her. i noticed i was a little to close before changing lanes... my sensor signal beeped like crazy (i have it set on 3 front and back) and as i was into the lane change the car stopped on it's own and then rolled after the brakes disengaged, the engine speed decreased rapidly and you heard it in the cabin, mind you my foot was not on the brake at no time during this whole incident. the first thing i did when the car suddenly started to brake was look in my RVM to see who was behind me. luckily they were a car length behind. i thought it was cool the way it happened but then again it can be dangerous in other scenarios. i didn't know that you didn't need the PCS engaged. there is nothing wrong with the system except that it works a little too damn good.

SNiiP3R

iTrader: (3)

Glad you are ok! Mine was off at that time as well, because I do not have the "PCS" indicator on. Since yours was off as well and its still engaged, does that mean we can't turn it off completely?

sydtoosic

the front and back sensors on the bumper are to blame for our incidents... well actually the sensors on the front bumper are the culprits. have you ever been at a light and a pedestrian walked to close or in the proximity of the sensor and the beeping starts? it acted the same way when i got to close to that car. it can be set, but mine was already at 3 which is the farthest away from an object in front or behind you... which means i was damn close to the other cars bumper (my bad). the way it just stopped startled the **** out of me at first. i don't know if we can disengage the sensors, but i'll check and see... that was a close one .

williakz

So, not PCS? Not A-PCS? Not Parking Assist? Not Lane Keep Assist? Not BCA or CBA or even ABC? Yet "nothing wrong with the system"? Just what "system" would that be and which video do we watch to see how it works or what brochure do we read to understand its operation?

"A little too damn good?" Nah, more like a lot too damn gullible!

sydtoosic

first thing in the morning i will go to Lexus and grab a tech and a service manager and explain step by step what happened today. i have not found any videos that extensively explain the inner workings of whatever system it may be that's causing this. i do know that i was too close to the car bumper in front of me before i changed lanes the gauge display just flashed lights and i heard the beeping. that was my fault for being to close and the sensors and beeping did what they were designed to do... it's the sudden stop that is a major concern. will let you guys know what the techie and service manager have to say. i'm also curious as to the term gullible... who or what were you referring to???

SNiiP3R

iTrader: (3)

^^^ I went to local dealer in Brooklyn when that happened to me. They said that they only have one person who might know something about these systems and he is not in today LOL...... My guess is their techs are not too familiar with these systems.

sam430

iTrader: (10)

There is a potential that the system may act weird for lowered cars. The sensor may pick up things now that it's closer to the ground.