Can I disable the knock sensors by unplugging them? Does anyone know if unplugging them will throw codes?

I'm having hesitation issues in my 07 LS 460.

Unrelated to oil change (have put about 4,000 miles on the clock since last oil change). Have run a few tanks of injector cleaner, cleaned throttle body, cleaned MAF. Running Toyota 5w-30 oil. New Denso spark plugs about 12,000 miles ago. I'm running the highest octane fuel I can buy.

Hesitation occurs almost every time I drive the car and seems to be triggered by low speed running or city traffic, car is fine on highway. I can avoid the issue by using ECT Power and keeping revs above ~2,000 rpm using the Sport/Manual mode.

Since the simple solutions (apart from manually driving the the thing) haven't helped, I'm guessing the problem is the valve guides talking to the knock sensors.

The last thing I will try is to get the Toyota dealer to re-flash the ECU (if it hasn't yet already been done). After that I'm looking at simple fixes like the knock sensors. Replacing the heads will cost more than the car is worth.

Thanks in advance for your help.

 

Don't know your service history/vehicle spec origination, but here are a few things to consider and/or check:

• I have an '07 also and the manual recommends 0W-20 or 5W-20. I've been using synthetic 5W-20 and car pretty much runs flawlessly. (0-60mph in 6.02 seconds and 1/4 mile in 14.16 seconds)
• Hesitation on Acceleration (L-SB-0033-08): as you mentioned, ECM may need to be updated/calibrated (see attached bulletin)
• Fuel rail/gasket safety recall - ELF Campaign: probably not causing your issue but more of an FYI (see attached)

Best of luck in tracking down the cause!

 

The car will throw a check engine light and run much worse with the knock sensors disconnected. Trust me, I’ve been there with an LS400 that had rodent damage to its knock sensor wire. I would clear the code on the highway, car would run much better, then after three seconds the code comes back and it felt bad again.

 

i had the issue as well and it went away completely after having the valve spring recall completed

 

What CEL code is that. Since its V you would have two knock sensors, you can possibly splice and send the signal for right ones to ECU, though I wont recommend it.

 

Talked to Lexus. Apparently the TSB to update ECU software is US market only and not available in other countries?

 

Thanks. I won’t try unplugging the sensors.

 

Have you found any answers on how to fix it without replacing the heads or buying a used 2013+ engine? I'm having the same issues. But today, it started having low idling issues. It'll go down to 400rpms and there's a loud smacking noise under the hood coming from under the intake manifold it seems.

 

I've not found any answers. I've started using OBD Fusion to monitor ignition timing - light throttle at about 1,200 rpm seems to be the danger zone where gobs of timing gets pulled. But only sometimes. Hence driving in Sport and Power modes I can avoid 1,200 rpm and the hesitation is not there.

 

I wanted to make my ClubLexus colleagues aware that L-SB-0033-08 "Hesitation on Acceleration" [2008-06-06, revised 2008-12-23 & 2012-07-18]

has been OBSOLETED & SUPERSEDED by

L-SB-0122-17 "Hesitation on Acceleration and-or P2119" [2017-05-03].

I did not discover this fact either in this forum or at the NHTSA website. Rather, when I presented L-SB-0033-08 to my dealership, they eventually provided in return a copy of the superseding L-SB-0122-17.

The major differences between the two SBs, as I read them, are:

* In the 2008 SB, the repair procedure calls for first performing the ECM flash … then conditionally (ie, if the hesitation is not resolved) performing the cylinder head replacements. The SB does not specify a cause.

* In the 2017 SB, the repair procedure calls for first performing the ECM flash (at steps 2 & 3) … and then, unconditionally, performing the cylinder head replacements (at step 4). The SB specifies the cause as "inappropriate spark knock or detonation detection."

This 'inappropriate detection' phenomenon is described with further clarity & detail at https://bit.ly/3ClAjBf .

 

I just spent a week reading through a bunch of these 'hesitation' threads. They contain a lot of experience & knowledge from other ClubLexus members. For what my opinion is worth, let me give you some suggestions for your consideration:

FIRST, plan on taking your concern to ANOTHER Lexus dealership. I know it might be inconvenient for you, but you apparently have seven others to choose from in New Zealand. If your dealership said "oh, that's the USA only" and then dropped you cold … instead of trying to further help you diagnose your problem … I'd read that statement as a 'blow-off line,' that they don't want to be bothered with spending a lot of time diagnosing your complicated problem only to find a solution that is so expensive that you won't pay for it … or perhaps even learning how to do a ECM/PCM flash. And just go back to doing more-profitable, less-complex work like replacing worn brake pads and blown water pumps and such. In today's world, some dealerships and service shops are just like that.

I am not a mechanic, but -- despite the circulating LSB stating USA market -- I would find it hard to believe that the ECM/PCM software (or the cylinder heads) is 'just an American' defect. The ClubLexus boards have quite a few owners complaining of this issue out of Canada, for example. It is reasonable to wonder if it is true that this Lexus engine had different valve guides installed in it based on what country it was being shipping to, especially different to New Zealand. And if it's got the same valve guides as everyone else, the ECM has likely got the same knock parameters to match as well. I hope you are catching my 'suspicion of doubt' here.

Second, I would call Lexus Corporate Customer Satisfaction. The minimum goal here would be to get a commitment from them that the ECM/PCM flash and cylinder head replacement is indeed of possible concern to your specific vehicle. If they tell you it CAN be a concern for your specific vehicle, now no one else can tell you it is not. Have your VIN handy. Describe your symptoms, share how your dealership responded and ask for guidance as to how to move forward. Get a case number; you can append your service experience to it as you continue to pursue a solution. Even under that circumstance, I wouldn't return to the dealership that told you 'USA only.' You can't force the dealership into being effective in helping you … if it's the kind of dealership that doesn't want to be. Just start fresh at another of the dealership that may treat you with better concern.

Third, don't trouble yourself thinking the cylinder head replacement is the solution you need, it's probably not. You are absolutely correct that the work is cost-prohibitive especially given the age & value of the vehicle. But ALSO because most all of the posters I saw in the threads said the ECM/PCM flash ALONE solved their issues, no replacements (such was my case as well). Only a few spoke of getting the cylinder head replacements (no cost under their warranties) … and of course that means they ALSO got the ECM/PCM flash first. And at least one poster said a technician said the replacements were rarely needed. So it's pretty likely you don't NEED cylinder head replacements to solve your problem.

Fourth, Toyota Genuine Motor Oil 5w30 does NOT come as a synthetic … and you might benefit from using some synthetic. With TGMO 5w30, you are getting mineral/conventional/dino oil. And conventional oil tends to ALLOW varnish & sludge deposits to accumulate, while SYNTHETIC oil tends to lift/clean such deposits. This is at the heart of the 'hesitation after oil change' issue that others are discussing. That varnish & sludge deposits from around the engine is dislodging, drifting then proceeding to clog the VVT (Variable Valve Timing) oil strainers and interrupt proper VVT operation that is dependent upon sufficient oil pressure. Without proper VVT, the timing of the engine is 'thrown-off' and delivers hesitation. Synthetic oil has detergents in the oil that can help finish dissolving/absorbing the deposits clogging the strainers. It could be that prior owners were flip-flopping between synthetic and conventional, with the synthetic lifting-up the sludge and dropping it in the strainers, then the conventional (such as what you have now) having less ability to dissolve it. These strainer deposits can move around somewhat at random by whatever cause (perhaps, in your case, sometimes, by light throttling in the 1200rpm range), effecting blocking then unblocking of the strainers.

So consider changing out your oil with a high-quality full synthetic oil change & filter … and let it try to clean out your VVT strainers. It may take some time and/or multiple changes. Member RoadFrog has been quite persistent in documenting that two oil changes of TGMO synthetic 0w20 basically solved this problem for him. There is a bit of risk to switching onto synthetic from a long history of conventional if the vehicle is super-high mileage, in that it might also clean-out sludge that is preserving oil seals and such, so take that into consideration in your decision.

Fifth, the symptoms you are describing actually seem to fit best with needing first "Safety Recall ALE 'Valve Spring Replacement' [2010-06-10]." … based on what I have read in the threads. At least here in America, that recall does not expire and is at no-cost to the owner. You can check the vehicle's history at LexusDrivers (or have a service writer do it) to see if it has (or has not) been performed. Some owners reported they also needed to apply the ECM/PCM flash after that, but not all.

Sixth … a distant sixth … did your problems start shortly after the Denso plug swap? eBay and Amazon are bursting with cheap counterfeit Denso plugs that fail easily. The only reliable sources for them are your Toyota & Lexus dealerships … and any 'national distribution partners' listed at the Denso website. Counterfeit Densos MIGHT be causing your issues … but really your symptoms fit much, much better with the other solutions discussed above.

My 'instinct' is that you are most likely facing either (1) the need for finding a dealership that WILL perform the ECM/DCM flash and/or (2) the need to get sludge deposits out of your VVT strainers. Both, in their own way, will pull your timing until you hesitate.

Persistence defeated hesitation problems most of the time, at least that's what I saw in the threads.

Happy motoring!

 

RESOLUTION OF MY OWN HESITATION ISSUE

My experience with the hesitation issue was pretty straight-forward. My recently-acquired 2007 LS460 (with 119k miles) delivered about 2 seconds of idling-delay in response to my flooring the gas pedal to demand full/urgent acceleration. That's really the only hesitation symptom I noticed. The 'Safety Recall ALE' VSR work had been done at 35k miles, quite some time ago.

When scheduling a brake fluid change/bleed at my local Lexus dealership, I also described my hesitation symptoms and presented the 2008 Lexus Service Bulletin L-SB-033-08 to the service writer. A couple of days later, the service writer reached out to me with the superseding Lexus Service Bulletin L-SB-0122-17. The Repair Procedure in that 2017 Bulletin requires an ECM/PCM flash, followed by (an unconditional) replacement of the cylinder heads.

I explained the age and value of the vehicle was such that I would not authorize the cost or risk of any cylinder head replacements. I also reinforced the 2008 Bulletin required such only if the ECM/PCM flash did not resolve the problem. I also mentioned that many members of ClubLexus reported that the ECM/PCM flash by itself had resolved their problem … and as a prior owner of a 2006 Toyota Avalon, I had experienced almost the exact same issue and that a similar Service Bulletin issued around the same time as L-SB-033-08 resolved that problem with only an ECM/PCM flash. So, in essence, I was encouraging the service writer to find if it was possible to proceed with the ECM/PCM flash only.

I was quoted a diagnostic fee of about $175 for the shop to determine how they could/would proceed. On that basis I scheduled-in, and eventually dropped, the vehicle for the hesitation issue (and the brake fluid change/bleed). At the end of the first day, I was told the vehicle would be held for a second business day while the service shop management continued to determine how it could/would proceed; I'll guess they were reaching-out to Lexus USA for advice (as to whether they could safely apply the ECM/PCM flash without any risk of really having to do the cylinder heads) and were awaiting a response. The service writer called early on the beginning of the third business day to inform me that the ECM/PCM flash (only) had been applied, that the hesitation symptom/problem was resolved and that I could pick up the vehicle.

When I picked-up the vehicle and closed-up the work, the service writer deleted the entire diagnostic fee and instead charged only for the ECM/PCM flash itself, written-up at 0.4 labor hours and a charge of $74. Perhaps placebo, but it feels as if the vehicle drives a good bit more smoothly overall … and it looks like I might have picked up at least a 1MPG (solid-city stop-and-go) improvement as well.

And the brake fluid bleed/change (@ $190) got rid of the "clunk-clunk" emanating from the (infamous) brake actuator whenever I worked the brake pedal. For the moment, I'll guess that the prior owners were seriously skimping on intervals and/or having them done lower-cost at non-TechStream Goober's Garage. So, for now at least, I am good-to-go regarding the brake actuator as well.

All-in-all, a productive & worthwhile dealership visit. Happy motoring!

 

I had the hesitation issue with my '07 LS460 several different times coincident with an oil change. The problem disappeared each time after I drove the car a few hundred miles. I never did anything differently other than drive carefully for a little while. We've seen lots of reports of widely varied corrective actions with reporters being certain that their "cure" identified the cause and was a certain remedy. Just because the "condition" goes away when the memory is flashed or some other thing like changing to a different oil, is really not proof that actions produced the results. I like to ask if the hesitation issue would prevail long term if you didn't do anything except to just continue to drive your car. We have no reports that it continues long term, just that it goes away with most anything you do. The contention that it is related to knock sensors seems reasonable to me. The cure is likely expensive, or Lexus would have solved this long ago. I suspect it is related to piston slap.