Knock Sensor SC430 Help!

[Smather]

Hi there everyone, just wanting some advice if possible.  My SC430 has an engine warning light and is currently in limp home mode - essentially little power and chews through petrol.  I recently sent it to a jap car specialist that fitted most of the mods and on their tester the fault cleared and they felt all was ok.  I had previously had it tested by Lexus in Glasgow who suggested it was a knock sensor fault.  The jap car specialist felt it was not a knock sensor fault and just needed to be run on the high end petrol.

The car is now back and the warning light is back on and we are limping around.  I have a couple of questions / observations. I have read online that you can splice the faulty knock sensor wiring onto the good sensor - personally not an option for me as I am not keen on messing with the wiring.  Another option is to have the knock sensors replaced - I have also seen online where people have done this and the issue hasn't been resolved....  The car had been sitting unused for a few years so I am wondering if there is sediment in the fuel tank and running ten tank low may bring on the issue... any thoughts or advice?

Also on a separate note, anyone having luck with OBD readers on imported sc430's as mine just won't connect.

Thank you for taking the time to read this!

[steve2006]

Hello and welcome to the LOC.

Do you have any fault codes from either or both places where you have already taken the car as these will save you both time and money when it comes to making the correct diagnosis, admittedly Lexus vehicles can be a little fussy with OBD readers and other members can generally recommend one that does the job.

The knock sensors are mounted under the intake manifold so are not easy to access but rarely fail.

With the car being sat so long unused the remaining fuel in the tank will by now be completely useless, how much fresh fuel have you added since? It may be worth draining the tank completely,replacing the fuel filter then refill with fresh fuel but the fault codes are definitely needed first.

 

[Smather]

Thank you Steve for your reply.

Lexus Glasgow in November tested it and said it was one of the knock sensors.  Subsequently the Jap car specialist I sent it to out their tester on and said there were no faults however the engine light is back on and it is in limp home mode.

When I put my reader on it it fails to connect - can anyone recommend a reader that will work on a Jap import?  My local garage has connected their Snap on reader and they can't connect either.....

I have a full tank of super unleaded so maybe a change of fuel filter could help?!

Regards

Sheridan

 

[TigerFish]

 

I had a knock sensor fail on My GS430 Sport. Changed the one relating to the fault code and problem was resolved. Does need the inlet manifold off, but wasn't too bad a job all in all. I ordered replacement inlet gaskets and throttle body gaskets, but I recon the old ones would've been fine.

 

 

Have you tried any other code readers, or just the one? Where are you located?

 

 

 

Sent from my Iphone using Lexus OC

 

[Smather]

Hi Tigerfish, I have 2 readers and my local garage has a more sophisticated one and none of them will connect....

Thank you!

[TigerFish]

Fair enough. I guess another trip to Lexus to get the specific code is probably the best option. The knock sensors aren't especially cheap so knowing which one it is would be handy, but you could do both. I'd give the starter motor an overhaul while the manifold is off just to be on the safe side.

 

 

Sent from my Iphone using Lexus OC

[Neil E]

Yes, in this instance it's probably best to get Lexus to read the codes.

It's a while since I used my OBD2 software so I'm not the best placed to give advice but Techstream seems to be the recommended product. The latest version has limited ability with pre 2005 cars so you may need to do some more research to see if there is an earlier version that works fully. If the car is using lots of fuel, doesn't that suggest the fuel flow is okay? It's rare to hear of a knock sensor. 

Without the codes we're just speculating but it seems strange that the Jap specialist was able to clear the error codes for any length of time. When it left their workshop was the car actually running okay or was it still 'limping?' I wonder if there is a bad connection to one of the knock sensors or MAF sensor.

[TigerFish]

 

When the knock sensor failed on my GS, it could be cleared and only come back when giving the car some beans, i.e. a decent amount of load . If driven gently, the light would stay off.

 

 

 

Sent from my Iphone using Lexus OC