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LC 200 Limp mode & Fault codes


JDMc
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Hi Fellows.

I am in need of some help to identify the cause of my LC200 VX 2007 model problems.  I would appreciate any info that other owners might have experienced and their outcomes on fixing it.

On a recent trip around the snowy area over the course of a week about a month ago, my truck went into limp mode 7 times. I disconnected the battery to reset the vehicle and then was able to drive on. I was unable to get to a Toyota dealer in limp mode, when I did, the vehicle was not showing any fault codes and was told they need it in limp mode to get the codes. The dash warning lights that came up were, VSC, 4lo, Slip indicator, Malfunction Indicator lights. and was only drivable up to about 50 kph.  On the drive back to Sydney the truck was fine.

In Sydney my mechanic suggested the fault might be the EGR, so I had it removed and cleaned. A week ago (Sun 21 Feb) while departing Sydney with my 3½t caravan in tow the truck went into limp mode again, this was the first time with the van attached, (obviously it’s not the EGR) my mechanic said this can sometimes happen as the vehicle’s computer relearns the engines performances. A couple of days later I set off again, on approaching Goulburn it happened again. The truck did not have the power to pull the van up the last hill into Goulburn, so I unhooked the van and drove to Toyota in limp mode. The scan show up the fault codes P0046, C1201, B1421, B1424, and B2312. (The 4 last codes don’t apply to my vehicle, so I’m led to believe, they’re probably from the previous vehicle scanned.) The scan indicated the injectors values are OK, suspect fault with turbo boost control. Toyota suggested returning to Sydney and have it repaired here. On the way home it went into limp mode 3 times, once while the truck was stopped at traffic lights. I am now trying to collect any info re this problem so I can make the right decision on what to do. To date the truck has gone into L/M 13 times.

Let me say it’s very daunting driving along the Hume H/way doing 50k an hour and trucks passing you doing 110km.

Many thanks for your help. 

John Mc.

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Hi John,

Do yourself a favour - go and buy a Scangauge - http://scangauge.com.au/

It is easy to install (literally plug it in, under the dash) - It will give you the codes - it gives you the capability to reset the codes (without disconnecting the battery) and gives you a stack of other useful info.

With that said - the type of fault you are talking about, could be as simple as a loose or worn wire, shorting somewhere.  Incredibly difficult to find. (I know - that isn't very helpful - sorry..)

I looked up the codes - and  P0046  doesn't appear in (my version of) the LC200 Diagnostic Trouble Codes that I have (mine was produced for the 2008 model, so should be the same as yours).  The codes on either side talk about "Oxygen Sensor Heater Control Circuit High" and "Oxygen (A/F) Sensor Heater Control Circuit Low".  They appear to relate to the air/fuel, mixtures relating to EFI and ECM modules.  I am sorry I don't have the details of the exact code you are experiencing.

I can only good luck in your search....

Regards

 

 

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Hi Geoff,

Thanks for your reply. I think I might invest in a Scan Gauge, could be very handy. The P0046 code I got from a Toyota Goulburn, so it might be only applicable the 2007 model.

I will advise the outcome, let’s hope it’s simple. :smile:

Regards John.

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  • 2 years later...
  • 1 month later...

Yes. I finally got a solution. My fault code was P004D - same as P0046 but refers to Circuit B rather than A. After 2 and a half weeks with the mechanic and lots of research I now have a pretty good understanding of this error code and causes and solutions. Hope this can help someone else who has this problem. 

These two error codes are tripped when the current from the stepper motor driver to the stepper motor exceeds 4.6 amps for more than half a second. The computer shuts down the system to protect things from further damage and wiring burnout and consequently puts the car into limp mode. 

Causes of the error are either a fault with the stepper motor driver, a short in the wiring to the stepper motor, a short in the stepper motor itself or the stepper motor faulty and drawing too much current. 

In my case the vanes of the turbo (which the stepper motor drives) were stuck and the stepper motor was drawing too much current trying to move them and so tripped the error code. The solution was to replace the turbo and stepper motor. Not an easy job since you have to drop the front diff to get at the turbo on the LHS. (Apparently for the RHS you need to remove the oil sump which again is not an easy job). 

I made the mistake of getting an aftermarket stepper and turbo assembly ($1600 instead of $3600 for the genuine unit which I believe is IHI). After reassembly the fault disappeared for 20 minutes and then returned putting the car back into limp mode and totally confusing me and the mechanic. At this stage I was up for $3400 which included an oil change, coolant change and having the EGR valve removed and cleaned ( this was a preliminary step while waiting for the turbo to be delivered- I was told that a dirty EGR valve could be the cause and although it was reasonably dirty, it wasn’t contributing to the problem in my case). 

We had eliminated the stepper motor driver being faulty. The driver is accessible by removing a plate from under the car just behind the RHS headlight. It’s easily removed and consists of two independent drivers for circuit A and B. Swapping the cables from one to the other will result in either the same error code if the fault is NOT in the driver, or the opposite error code if one of the drivers is faulty. 

The mechanic told me that the only other thing it could be was a fault in the wiring but he’d have to drop the diff again to check. At this point I took the car back to my camp site and did my own testing. 

I tested the old stepper motor and it seemed to be working ok. Applying 12v to the input pins and then reversing them caused the stepper motor arm to move backwards and forwards as it’s meant to. However I wasn’t able to determine whether it was drawing too much current. (We later put this old stepper motor back on the new turbo and it immediately tripped the error code and so was definitely faulty. )

I then removed the stepper motor driver and did some testing on the wiring of each circuit. There are two sets of wires - one with 4 thicker wires and a larger set of 8 thinner wires. After some time I was able to conclude that thicker wires are - for circuit B - the positive (red) and negative (black) - providing current via the driver to the stepper motor- the other two blue and white - which go directly to the stepper motor. (Circuit A wires are similar colours but striped). The resistance across the blue and white should be 2 to 3 ohms which it was in both sides of my wiring for circuits A and B. However there should be more than 10K ohms between each of the blue and white wires and ground. I found that this was the case for the 2 wires in circuit A but in circuit B one wire showed 0 ohms and the other 2.5 ohms. Conclusion is that there is a short circuit somewhere between the driver and stepper motor. Luckily the plug on the LHS circuit stepper motor is accessible under the wheel arch after removing the rubber flaps. Not easy to remove this plug but with a very long screw driver I was able to get it off. Then tested the resistance across the blue and white wires and found an open circuit. So the short was not in the cabling. Tested resistance of both wires to ground and again open circuit. So I concluded there was a short inside the NEW stepper motor. I was able to confirm this by getting a lead to the stepper motor pins - not easy but doable. 

So back to the mechanic who dropped the diff again, removed the stepper motor which I dissembled and found that one of the solder post for the motor was touching the case. After filing this back and reassembling the stepper motor all was good  no more error codes. Out of interest we put the old stepper motor back in but it threw the error code immediately and so was obviously damaged trying to push the stuck turbo vanes. Another $800 labour cost and we were back on the road  

This long, expensive process would have been simpler and quicker if we’d bought the genuine turbo assembly. The quality of the interior of the original stepper motor is far superior to the cheaper aftermarket one that I bought. Lesson learned!

hope these details help someone else in the future as there is very little information available on the web.

A useful site for diagnostic of some of the error codes associated with the turbo: http://www.autocats.ws/manual/toyota/tlc200/rm0810e/MANUAL.HTM/rm0810e/repair2/html/frame_rm0000031hw003x.html

and http://www.autocats.ws/manual/toyota/tlc200/rm0810e/MANUAL.HTM/rm0810e/repair2/html/contents/rm000002ppl007x.html. However some of the details in this diagnostic chart are incorrect. The part of the flow chart that indicates the error code in the driver is back to front. Also the numbering of the 4 thick wires connected to the stepper motor driver also seem to be incorrect. 

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