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SRS Light On - Occupant Detection ECU
I had the SRS light come on my 2007 SC430 and took it to the Lexus dealer. The dealer stated that the problem was caused by a bad "Occupant Detection ECU" located under the right front/passenger seat cushion. The dealer wanted to replace the entire seat cushion assembly for "please sit down" $1,880. I declined until I could do some research. Has anyone else experienced this problem? After doing some research, it appears that the ECU can be purchased rather than the whole seat cushion assembly. I believe that the part number is 89952-0W040 for the Occupant Detection Computer and costs around $325. Has anyone ever changed this ECU? Thoughts? I am willing to give it a try, but wanted to get some thoughts from you first. Thanks in advance!!
https://cimg8.ibsrv.net/gimg/www.clu...76297fceb1.png |
Never had this problem but if I were you I would first verify the diagnosis wtth second source, scan tool or Techstream. If it’s verified then purchase the ECU. Replacing the ECU under the seat probably not difficult.
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Good idea...I will get the verification of the problem. I will probably take the seat out to check all of the connections before purchasing the ECU.
Thanks! |
Getting a second opinion is always a good idea. If it comes back with a bad module, then you can probably change it yourself.
People are hesitant to mess with the SRS system because of the potential damage an expanding Airbag can do. This is a justified fear. However, once you disconnect the power source, then the chances of the airbag deploying is greatly reduced. The internet way to do this is to disconnect the battery and wait 10 minutes, or disconnect the battery and turn on the ignition. Or disconnect the battery and touch the two battery cables together. I do not know if any of these things will actually discharge the electrical system, but that is what the internet says. YOU SHOULD DO YOUR OWN RESEARCH THOUGH. Once the system is discharged, you should be able to put in a new seat module. The great thing about the SRS system is it does a self check every time you turn on your car. You will know if the new module solved the problem. Something else I heard on the internet is; after you replace the module, you can turn your ignition on and reconnect the battery. This way if the airbag deploys, you are no where near it. Again you should do your own research on the SRS system. One more random note. My dad's Mercedes has a primary battery and a backup battery for the electronics. That means you probably need to disconnect BOTH batteries if you decide to buy a Mercedes and tackle the SRS system in it. |
Hmmmm...it’s just my opinion.... Regarding the occupant seat sensor and why they are SO expensive. Changes to the technology came about in 06 and later models due to concerns about passenger airbags and the velocity of airbags in general. Inside the seat, not only will find the seat ECU but there is a pressure sensor too. Typically a silicone-filled "bladder" that registers air pressure when someone sits on the seat. When someone sits the pressure sensor signals the occupant's weight to the ECU. The ECU then sends that data to the airbag’s computer, which has its own control unit. Based on that information, the vehicle's computer turns the passenger airbag on or off. Some OCS don’t just detect weight. They read the passenger's seating position and determines if they're wearing a seat belt. Some also have a seat belt tension sensor that allows the OCS to interpret the pressure created when or if a child seat is fitted. In other words, the system is designed to tell whether a child safety seat is occupying that seat or whether you're just carrying some heavy object there. Then, the instrument panel tells the driver whether the passenger airbag is on or off. Once the onboard computer generally determines the passenger's size and weight, the car's computer can regulate dual stage airbags. These type of airbags can deploy at full speed, partial speed, or not at all. Deploying at full speed can badly injure or even kill a child or small adult. Dual stage airbags also can deploy at lesser speeds when the car is involved in a minor collision. In my opinion the liability issues of improperly servicing technical safety equipment can easily outweigh any cost savings obtained. In other words, the problem here could be, for lack of a better way of describing it, a leaky bladder, and not necessarily bad electronics. This is probably the reason for the sky high repair estimate. I don’t believe there is a safe way to determine the exact problem without tearing the seat apart. So Lexus recommends replacement. Of course it’s your choice as well as your risk. |
While this is a very general statement I believe it’s true: most car manufacturers don’t make or build their own seats. They are contracted out to specialists or vendors with seat engineering experience.
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Originally Posted by VVTiBob
(Post 10418013)
Hmmmm...it’s just my opinion.... Regarding the occupant seat sensor and why they are SO expensive. Changes to the technology came about in 06 and later models due to concerns about passenger airbags and the velocity of airbags in general. Inside the seat, not only will find the seat ECU but there is a pressure sensor too. Typically a silicone-filled "bladder" that registers air pressure when someone sits on the seat. When someone sits the pressure sensor signals the occupant's weight to the ECU. The ECU then sends that data to the airbag’s computer, which has its own control unit. Based on that information, the vehicle's computer turns the passenger airbag on or off. Some OCS don’t just detect weight. They read the passenger's seating position and determines if they're wearing a seat belt. Some also have a seat belt tension sensor that allows the OCS to interpret the pressure created when or if a child seat is fitted. In other words, the system is designed to tell whether a child safety seat is occupying that seat or whether you're just carrying some heavy object there. Then, the instrument panel tells the driver whether the passenger airbag is on or off. Once the onboard computer generally determines the passenger's size and weight, the car's computer can regulate dual stage airbags. These type of airbags can deploy at full speed, partial speed, or not at all. Deploying at full speed can badly injure or even kill a child or small adult. Dual stage airbags also can deploy at lesser speeds when the car is involved in a minor collision. In my opinion the liability issues of improperly servicing technical safety equipment can easily outweigh any cost savings obtained. In other words, the problem here could be, for lack of a better way of describing it, a leaky bladder, and not necessarily bad electronics. This is probably the reason for the sky high repair estimate. I don’t believe there is a safe way to determine the exact problem without tearing the seat apart. So Lexus recommends replacement. Of course it’s your choice as well as your risk. |
My fear of the airbags is gone now. But my respect for them is certainly present. recovering the seats in my SC430 and my Accord made me realize it is fine to work on them if you follow the CAUTIONS. once discharged, air bags won’t deploy without a trigger voltage. i would certainly look under the seat to make sure the yellow connector is still attached...if not, disconnect the battery for 10-15min then reconnect it...check the drivers side too. if I remember correctly, the drivers side has two connectors and passenger has three. |
I don’t recall the ECU but I am sure it was there... you can reference my seat pics in this thread. https://www.clublexus.com/forums/sc4...-interior.html |
I wanted to give everyone an update about the SRS light "ON" on my 2007 SC430.
I did verify with my local Lexus dealer that the Occupant Detection Computer (Part 89952-0W040) was bad...the software/data was corrupt. Evidently this is not common on the SC430s, but I was told that is has been more common on the IS models. So, I purchased a new ECU from discountpartsmonster.com (great place to buy oem parts by the way). Installed the ECU myself and took it to the local Lexus dealer to have them calibrate to my 2007 SC430. Upon taking my car to the dealer, they said that they could not do it because "Lexus" does not have the software/data to load onto the new ECU and that they would need to wait until an SC430 came into their shop so they could get the software/data from that car and then they could load on to my new ECU. I said well, I have another SC430, but it is a 2005. I was told that should work and I was instructed to bring in both my 2005 and 2007 into the dealership so they could copy the information from my 05 to my 07. I asked...you are sure these are compatible? They said yes. So, I brought both of the cars into the dealership this morning and guess what....the 05 info is different from the 07. What a waste of my time and theirs. I was told that they need the software/data from an SC430 from 2006, 2007 or 2008. And to top things off, now my 2005 SC430 has both of the VSC and VSC OFF lights are on that I will need to take back to them to fix/clear codes (zero point calibration probably needed). I am starting to lose confidence in the one and only Indianapolis local Lexus dealer :sad: The good news is that the dealer has not charged me anything yet. I am told that Lexus no longer has this software/data available! What??!! So the dealer stated that we would need to wait for a 2006-2008 SC430 to come into their dealership to get the software/data from that car's Occupant Detection Computer (Part 89952-0W040). This could take weeks or even months....assuming that my service adviser will even remember to get the information. So, I looked around locally for a 2006-2008 SC430 for sale in hopes of "borrowing" the car to get the data/software. My next option was to find a Lexus Dealer that has a 2006-2008 SC430 on their lot that is for sale to see if they would be willing to get the software/data from that car and send to me or my Lexus Dealer. I did see that Sewell Lexus has a matching SC430 on their lot. Not sure what they would charge me to do this. It would be nice if my Lexus dealer would go to this small amount of effort to provide this service :) I would really like to get this resolved....anyone have any other ideas? Thanks! Jeff |
Originally Posted by Indianajef
(Post 10469975)
I wanted to give everyone an update about the SRS light "ON" on my 2007 SC430.
I did verify with my local Lexus dealer that the Occupant Detection Computer (Part 89952-0W040) was bad...the software/data was corrupt. Evidently this is not common on the SC430s, but I was told that is has been more common on the IS models. So, I purchased a new ECU from discountpartsmonster.com (great place to buy oem parts by the way). Installed the ECU myself and took it to the local Lexus dealer to have them calibrate to my 2007 SC430. Upon taking my car to the dealer, they said that they could not do it because "Lexus" does not have the software/data to load onto the new ECU and that they would need to wait until an SC430 came into their shop so they could get the software/data from that car and then they could load on to my new ECU. I said well, I have another SC430, but it is a 2005. I was told that should work and I was instructed to bring in both my 2005 and 2007 into the dealership so they could copy the information from my 05 to my 07. I asked...you are sure these are compatible? They said yes. So, I brought both of the cars into the dealership this morning and guess what....the 05 info is different from the 07. What a waste of my time and theirs. I was told that they need the software/data from an SC430 from 2006, 2007 or 2008. And to top things off, now my 2005 SC430 has both of the VSC and VSC OFF lights are on that I will need to take back to them to fix/clear codes (zero point calibration probably needed). I am starting to lose confidence in the one and only Indianapolis local Lexus dealer :sad: The good news is that the dealer has not charged me anything yet. I am told that Lexus no longer has this software/data available! What??!! So the dealer stated that we would need to wait for a 2006-2008 SC430 to come into their dealership to get the software/data from that car's Occupant Detection Computer (Part 89952-0W040). This could take weeks or even months....assuming that my service adviser will even remember to get the information. So, I looked around locally for a 2006-2008 SC430 for sale in hopes of "borrowing" the car to get the data/software. My next option was to find a Lexus Dealer that has a 2006-2008 SC430 on their lot that is for sale to see if they would be willing to get the software/data from that car and send to me or my Lexus Dealer. I did see that Sewell Lexus has a matching SC430 on their lot. Not sure what they would charge me to do this. It would be nice if my Lexus dealer would go to this small amount of effort to provide this service :) I would really like to get this resolved....anyone have any other ideas? Thanks! Jeff you said the part is installed, is the SRS light still on? |
Originally Posted by Bgw70
(Post 10469996)
sorry to hear how difficult this is for you. I was just wondering if you installed this part from a used 2006+ SC430. Would it already have the programming you require? you said the part is installed, is the SRS light still on? Evidently, the brand new ECU unit does not come with the required programming. The SRS light is still on. The Lexus Dealer needs to get the required programming from a 2006-2008 Lexus SC430 and then install the programming on to my new ECU. Thanks, Jeff |
Originally Posted by Indianajef
(Post 10470018)
The ECU was a Brand New Lexus OEM ECU Part Number 89952-0W040.
Evidently, the brand new ECU unit does not come with the required programming. The SRS light is still on. The Lexus Dealer needs to get the required programming from a 2006-2008 Lexus SC430 and then install the programming on to my new ECU. Thanks, Jeff i still find it odd they cannot program the ECU. What they are telling you is strange. so basically, they can’t help you because your car is more than 10 yrs old. have you thought about calling another dealer to get a quote to perform this programming. That way you could see if they tell you the same thing. |
BTW, the VSC light on happens anytime you plug something into the OBDII connector...2002-2005. 2006+ has a different bus type. just take a paper clip and, plug it into OBDII pins 4&14, turn the key on for 5-10 seconds, turn the key off Remove paoerclip. now go drive...VSC lights are off. for more details, click on the link below, read post #5, then go to post #38. https://www.clublexus.com/forums/sc4...l#post10232997 |
I’m sorry but this sounds really odd. TIS should have all the data for all the different ECUs in the car. While it’s true the dealer doesn’t have it, they DO have access to ECU data via TIS. This is how Toyota gets the latest software updates to dealers. Is the dealer claiming they have it or they don’t have access to TIS? If it’s the latter I’d run away from that dealer. |
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