P1700 code: Speed Sensor inside transmission?

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lettereleven

lettereleven

10 Year
Joined
Apr 1, 2013
Threads
35
Messages
134
Location
Vancouver, BC
I have a P1700 code on my 97 LX450. I've followed the FSM to check the #2 Speed Sensor, the wiring, and even gone so far as to replace the ECU. The code keeps coming back!

I took it to Lexus and their conclusion was that the "part" of the sensor might have fallen off inside the transmission; something they have "never ever seen before".

My question to the community is: has anyone heard of the speed sensor breaking inside the tranny? If so, can you share your story?

Thanks very much,
Jamie.

(desperately trying to get my 450 to pass an annoying compliance inspection so I can actually insure/drive it).
 
If the sensor itself and wiring is fine there is a reluctor ring that is part of the transmission. Similar in function to an abs reluctor ring.

No idea what would cause that to break, other than exploding bits inside the trans itself. Has the transmission been apart before?
 
Thank you for the insight. I dont have any history on the truck - just got it and the previous owner was a flake so no help there!

Any thoughts on intensity of the repair (scale of 1 to 5 kinda thing)?

Just need to brace myself.

Cheers
 
Used transmission would be the quickest repair. Maybe do the rear main seal and oil pan arch if its already apart.

Taking apart a transmission that may have broken bits inside is not something that I would want to do, only to have to do it again if/when there's another internal problem. I don't have the guts to do stuff like that.

Welcome to the madness.
 
Well, it wasnt me personally. I supplied the FSM to my technician friend and he followed the protocol outlined. He suspected maybe it was the ECU, but suggested taking it to Lexus so they could confirm either way before I spent the cash on a new ECU.

Lexus also ran their diagnostic on the sensor (outside the transmission), the ECU, and messed about with the wiring. I think they read the same page in the FSM because they suggested changing the ECU, which I did. The code came back. Lexus concluded that the only thing in their mind could be something in the transmission (reluctor ring per @86tuning).

What are you thinking?
 
I'm thinking you have a wiring issue and need to find someone with experience trouble shooting this sort of thing.

what I would do is this:

Clip your +lead on the ECU connector C2 and -lead on C8. Set the VOM for continuity tone and wave a magnet over the sensing end of the sensor.

If the meter tones with the passing of the magnet the circuit is OK
If the meter tones all the time the wire connected to C2 is shorted to ground.

If the meter never tones remove the connector from the sensor and jump across the two pins in the connector. Still no tone you have a break in the harness, if the meter tones you have a bad sensor.

all this shouldn't be more than a half hour or so. If the problem is in the harness that would be the worst case as you now need to locate the break.
 
Thank you very much for the detailed approach. I will definitely give this a try (with help). I have nothing to lose by investigating further.

Updates to follow for future searchers.

Thanks again,
Jamie.
 
That by no means is an end all procedure for testing the entire circuit and all the possibilities of what could go wrong. But it should provide some direction to where the issue is.

I mentioned using a magnet be cause some one else indicated that was the type of sensor it was. It could very well be a sensor that would react to an iron base metal so waving a screw driver shaft across the end might be the trigger for it. I'd try the screw driver first.
 
A decent scanner will tell you if the ECU is seeing a vehicle speed signal. I'm sure Mr. T SHOULD have the right scanner to see this. I just don't trust stealerships to do the right thing. I'm 99% sure my AutoEnginuity software reads that sensor without the Toyota specific package.

Either the ECU sees it or not. If it does NOT see it, then it is a sensor/wire/tone gear problem. I would say that because you used two separate ECUs with the same problem, it is a wire/ sensor problem. The FSM shows a 4 "toothed" gear on the output shaft of the transmission that the sensor reads off of. With the help of a mirror, you should be able to see those 4 teeth pass by the hole where the sensor would be after pulling it out. If the 4 tooth tone ring is gone, then you know.

I had to replace the VSS (vehicle speed sensor)on a F250 once, and the tone ring on that was very easy to see. I am guessing that our transmissions would be the same.

The FSM says it is a two trip logic code. I think that means you have to drive the car twice before it turns the Check engine light on. Does your light come on immediately after resetting, or is it several trips/days later?
 
Can't believe a trans shop can't read a code on a 97 Lexus. I see your local swing by lees transmission on Hastings and Clark they should be able to scan it. If its an internal trans issue.
 
CJF said:
So, anyone know exactly what/where this "other" sensor (not the one attached to the t-case) is??
Click to expand...

From the parts schematic there are two if them mounted on the DS of the tyranny. Not the t- case which is for the speedometer.

Haven't done a visual yet though.
 
lettereleven said:
Lexus also ran their diagnostic on the sensor (outside the transmission), the ECU, and messed about with the wiring. I think they read the same page in the FSM because they suggested changing the ECU, which I did. The code came back. Lexus concluded that the only thing in their mind could be something in the transmission
Click to expand...

I would think that Lexus techs must be reasonably competent to work at Lexus. I would trust what they say, but ask if they looked inside the trans with a mirror or something to confirm that the reluctor is indeed broken.

If its the sensor in the back of the trans, it may be possible to access it by removing the transfer case.

The copy of the a343 manual that I have is very old and I can't seem to find mention of the sensor, except in the tear down pages at the front.

Where is the truck from? If its a USA vehicle and not just an out of province car, you may be able to pin the cost of repairs on the seller if there's an emissions related problem (engine check-light should qualify) but check the laws where it came from.

Disclaimer: I know a couple guys that work at Lexus dealerships (not locally) and they're pretty competent people. They didn't get there by being incompetent. I would think that the tests that land tank mentions would have already been done. Then again, my faith is pretty strong lol.
 
86tuning said:
Then again, my faith is pretty strong lol.
Click to expand...

Mine's not.

They already sold him an ECU he didn't need.

ANY time a thread starts with "I took it to the dealer and they said..." my BS meter immediately goes off.

I can honestly say that I could come up with at least a dozen cases here where a dealer said a member needed a new tranny, period, and the issue was something as simple as a stripped drive flange, or in one case I remember, simply a disconnected "kickdown" cable.
 
86tuning said:
I would think that Lexus techs must be reasonably competent to work at Lexus. I would trust what they say, but ask if they looked inside the trans with a mirror or something to confirm that the reluctor is indeed broken.

If its the sensor in the back of the trans, it may be possible to access it by removing the transfer case.

The copy of the a343 manual that I have is very old and I can't seem to find mention of the sensor, except in the tear down pages at the front.

Where is the truck from? If its a USA vehicle and not just an out of province car, you may be able to pin the cost of repairs on the seller if there's an emissions related problem (engine check-light should qualify) but check the laws where it came from.

Disclaimer: I know a couple guys that work at Lexus dealerships (not locally) and they're pretty competent people. They didn't get there by being incompetent. I would think that the tests that land tank mentions would have already been done. Then again, my faith is pretty strong lol.
Click to expand...
did they work at lexus in 97 or in the past 15 years since the lx 450 ha not been made? these trucks are not standard lexus issue and are different then many of the more recent iterations
 
englaneato said:
did they work at lexus in 97 or in the past 15 years since the lx 450 ha not been made? these trucks are not standard lexus issue and are different then many of the more recent iterations
Click to expand...

I'm not here to get into a pissing match.

I do know quite a few dealership techs that shouldn't be allowed to work on cars at all. I certainly would not let them touch mine.

However, a check-engine light problem would usually not go to those clowns. They usually go to master techs. Or at least the apprentices would consult the master tech.

When a Toyota or Lexus master tech says the problem is internal to the transmission, that's the direction I would go.

The repair manual procedure for that code looks like it was followed by TWO independent techs at two shops that came to similar conclusions: next step says try a known good ECM.

When that did not fix it for either tech, the next step is to re examine things.

I have seen abs reluctor rings break before and cause intermittent abs issues that are very difficult to duplicate and diagnose.

This sounds to me like one of those cases. Not a problem with the sensor, but rather the trigger wheel.

I'm not a magician and cannot verify this without looking at the car, but it seems to me a very straightforwards (but not cheap) repair.

The trick now is to find a good used transmission, locally, for a good price. Unless the part is in the tail housing and available new from the dealership, this is the direction I would go.
 
Oops, my mistake, re reading it shows that both techs wanted to try an ecu as the next step, but that wasn't done til at the dealership. Not that it matters at this point.
 
having been a field engineer for over 30 years, my perspective is that this circuit is about a 1.5 on a complexity scale of 10 being the most complex.

I honestly don't see a dealer tech being able to handle this without an inordinate amount of drama.

This is based on my personal experience. I bought a 96 locked 80 off of the lot of a dealer after getting the contact info of who owned it. All their best and brightest technicians looked at it and after 3 days it was deemed not repairable.

I got it for 1000.00 and had it running in 30 minutes. Corroded fuel pump connector under the DS passenger floor panel.

Point is, electrical problems takes a certain skill set to work through them and most dealers aren't going to pay the money needed for that skill set. They hire mechanics!
 
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