97 Camry Emission Diagnosis

[Babaloo]

Hi everyone,

I have some questions regarding a 97 Camry w/ 5S-FE (2.2L I4) A/T. The car did not pass emission due to a DTC.

Problems:
1. Check engine light on (P0500 Vehicle Speed Sensor Malfunction)
2. Speedometer and trip odometer not working

Here is the procedure from the 3rd gen (92-96) FSM:

BODY ELECTRICAL SYSTEM
SPEED SENSOR INSPECTION
Operation
(a) Connect the positive (+) lead from battery to terminal
1 and negative (–) lead to terminal 2.
(b) Connect the positive (+) lead from tester to terminal 3
and negative (–) lead to terminal 2.
(c) Revolve shaft.
(d) Check that there is voltage change from approx. 0 V
to 1 1 V or more between terminals 2 and 3.
HINT: The voltage change should be 4 times par each
revolution of the speed sensor shaft.
If operation is not as specified, replace the sensor.

Here is the picture from the FSM (BE-67) :

I followed the procedure on the 3rd gen FSM. When I connected all the wires (step a & b), the meter showed a steady 11v reading. I turned the wheel a few times (step c) and the meter stay at 11v. As you see, the FSM said that there should be a change of voltage from 0v to 11v. After I put everything back and started the car, the check engine light was gone but the speedometer was still not working. I am kind of confuse right now.

1. Any difference on the procedure between 3rd gen (92-96) and 4th gen (97-01)?
2. Did I follow the instruction correctly?
3. Did this mean the vehicle speed sensor is the suspect of the check engine light?
4.Why was the check engine light out while the speedometer was still not working?

What should be my next move?

Thanks in advance.

 

[brianl703]

I think the light will be back on soon. Did you disconnect the battery? (It takes two drive cycles to turn the light back on when a failure exists.)

It sounds like this is a hall effect type sensor and yes, there should be a change of voltage from 0 to 11 volts as you turn it, so I would suspect the sensor as the cause of the problem.

 

[kenw]

wait a minute: was the speedo NOT working when you took it in? If not, why did you bother? If so, perhaps something was knocked loose when the inspection was done (maliciously or not)

otherwise, ditto what Brian said.

 

[Babaloo]

Brian, Thanks for your input. I did not disconnect the battery at all. Since the car does not has a license, I did not drive it except to test the speedometer at 11:00 p.m. around the block. I am planning to apply for a 3 day permit and drive the car to Autozone and have them check to see if the P0500 code is still there. What is a hall effect type sensor? Also, about the 2 drive cycles thing, is this universal or Toyota specific?
Thanks again.

 

[Babaloo]

Kenw, yep, the speedo was not working and the light was on BEFORE the test.

My father just bought the car 2 weeks ago and the car was a mess. No plate, wheel stud broken off, 3 regular tires plus a spare, missing door handle, dead battery, the list goes on. He got the car and went straight to DMV, then came back and handed me the failure notice and a bunch of documentation. I didn't even know he buy anew car until he gave me the notice.
Anyone know why was the check engine light out while the speedometer was still not working?

 

[Drew99GT]

Speed sensor is different then hall effect sensor. The speed sensor is located on the output of the tranny and the hall effect is usually in the distributor and it basically tells the computer where the engine is at (in terms of which clyinder is where in the firing order) in relation to the crankshaft. If the speedo isn't working, that's probably your problem, speed sensor. Light is still out probably cause of what was said above; it was cleared when you got the code and it'll take a few driving cycles to re-emerge.

 

[brianl703]

A hall effect sensor is one common type of sensor used for sensing vehicle speed. A hall effect sensor is a magnetic switch and the output of a hall effect sensor will be either on or off (a square-wave output if viewed on an scope). These require 12V power to work, and usually connect with 3 wires.

The other common type of sensor used for sensing vehicle speed is a variable-reluctance sensor, which does not require power and has a sine-wave output, the frequency and voltage of which increases with vehicle speed. These connect with 2 wires.

There are other types of sensors, such as optical sensors, but I don't consider them common.

As far as the two driving cycles to turn on the light when there is a malfuction, I think that's an EPA or SAE standard.

EDIT: The hall-effect sensor can be used in a variety of speed/motion sensing applications in addition to distributor pickups. There are computer keyboards that use hall-effect sensors to sense keypresses.

 

[kenw]

basically because you reset it somehow. until it gets a new failure signal, it takes your word for it that you've fixed it.

a hall effect sensor is basically a device that sees a magnet and uses it's field to turn a switch off and on. usually a magnet is on the rotating shaft, as the shaft turns it makes the hall effect sensor go off-on-off-on.

the computer counts the number of off-on cycles in a period of time and sends that as a steady state voltage to the speedo.

if you replace the sensor and it still does not work, it could be that the wiring is damaged or worse, the magnet that makes the sensor work (and is mountied on something inside the trans or differential) is missing.

But with your diagnosis so far, my money is that the sensor is just bad. Pull this "bad" sensor and wave a magnet around the end of it to see if that makes the voltage change any.

good luck

 

[brianl703]

It sounds like the magnet is inside the vehicle speed sensor, since the instructions say to turn the shaft (presumably with the sensor removed from the transmission).

 

[Babaloo]

Thanks Brian, Drew and knew. knew, I think Brian is right on the magnet being IN the sensor. The 4 things that can go wrong and should be check or replace, according to the FSM, are speed sensor, comination meter, harness or connector between vehicle speed sensor, and the computer. Brian, I tested the sensor in the tranny. Should I take the sensor out to test it?
I will take the sensor off and try knew's magnet test on Thursday when I have my day off and post what I find. In the mean time, please keep the ideas coming. Thank you.

 

[kenw]

All i know is that the magnet and the sensor have to move in relation to each other, it's how hall effect sensors work. How it can do this and be in the same part I dunno but i guess it could be.

cars I've seen in the past (very distant past..) had the magnet mounted on the driveshaft. On one aftermarket cruise control I had to glue 4 of them on the driveshaft.

if it is another kind of sensor, well, i'm clueless. if it isn't hall effect, the magnet test i mentioned is useless.

Let us know what you find.

 

[brianl703]

I think there is a shaft, one end of which is driven by a gear in the transmission and the other end of which has a magnet mounted on it. The magnet-end of this shaft is in a housing that contains a hall-effect sensor, making a one-piece sensor. I'm pretty sure that's how Ford does their hall-effect speed sensors--Toyota is probably similar.

You might want to take the sensor out of the tranny just to verify that there isn't a problem with the drive gear or the driven gear on the speed sensor shaft.

 

[Babaloo]

Okay. I tried to test the sensor out of the tranny an hour ago. It did not read on the meter, not even 11v. When I put it back in the tranny, it read 11v on the meter. Then I sticked a kitchen timer w/ small magnet on the back in there and move it around. Nothing happened. When I plugged the connector back on, it did not feel snug. I could just pull it out without pushing on the tab. I checked both end and they were in good shape. So I put some duct tape on the connector as a temporary fix. I was thinking the loose connection may be at least part of the problem. The connector did not touch> no signal send to the computer> computer thinks the sensor is not functioning> DTC> Check engine light on. Does this make sense?
Here are my questions:
1. Does it matter if I measure the sensor in or out of the tranny?
2. How big a magnet should be used?
3. Is there a way to fix the connection between the connector and the sensor?
4. How can I find out if the sensor is a hall effect sensor or not?
I have also taken some pictures of what I have done this afternoon. I am going to upload them tomorrow when I am in my office. I am using 56K at home. Thanks a bunch for all the information and directions.

 

[kenw]

if the sensor is removed it may not be grounded, hence no voltage. try it again but ground it (the body) with a test lead.

virtually any size magnet will work, something off the 'fridge will do.

your bad connector scenario is very plausible. On the connector with pins, spread them apart very slightly, not so much that they will not fit but enough to press them against the side walls of the socket part. this may snug them up and make better contact.

 

[Babaloo]

I was gonna upload the pics earlier but could not find a USB cable. Anyway, here are some photos I took yesterday.

The magnet test setup (Meter @ lower left corner, timer w/ magnet @ top of the battery, sensor @ top of the radiator)

Speed sensor

Speed sensor location

quote:

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if the sensor is removed it may not be grounded, hence no voltage. try it again but ground it (the body) with a test lead.

---

kenw,
how can I ground the sensor? One end goes to the body and where should the other end goes to?
Also. Can you determine if a sensor is a hall effect type or not from its appearance?

 

[kenw]

OK, here's my guess: the sensor is inside the fat part near the oring. Still can't tell if it is hall effect of not, sorry.

You'll need to hook up the regular cable *AND* run a jumper wire (alligator clips) from the housing to the car chassis ground.

then do the test as prescribed in your book. 1st without the extra magnet, then with the magnet.

let me know what happens.

 

[Babaloo]

quote:

---

You'll need to hook up the regular cable *AND* run a jumper wire (alligator clips) from the housing to the car chassis ground.

---

kenw, just want to make should I understand, hook up all the wires like I did on my previous test and put a jumper cable with one end to the chassis (w/ alligator clip) and the other end on the metal part of the sensor (w/ alligator clip).

 

[kenw]

yep, that'll make sure it is grounded.

 

[Babaloo]

knew, thank you for following the post and spend the time to reply

. I will post the result tomorrow.

 

[Babaloo]

I tried the magnet test w/ the jumper cable again and still got the same steady 11v. I used the kitchen timer and my magnetic parts bowl and move around, from close to far and it just stay at 11v.
kenw, I think I am going to bend the terminal a little just like you said, then take the car to Autozone and have them check the code. This will also give the car a chance to run so the check engine light will come on if the problem is still there. If there is a code, I will get a used sensor. Of course, if the code is gone, I will just take the car to emission. What do you think?