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P056 can be fixed with engine-prm signal ???


Psycho

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Hi

just for my understanding.

The P056 can have 4 causes:

Electromagnetical coupling - spark, cb.....

Broken axle speed sensor

Defective wiring or connector problem

Gap between sensor and rotor to big (causes smaller signal)

So if the error is present you have to change the sensor.

That means to open the transmission.

But today I thought about a other possibility:

I meassured the signal on PD72 and the input speed Signal was the same, as the engine-rpm.

If this should be so in any driving condition, the problem can be fixed by routing the engine rpm signal to the

input of the transmission rpm.

Has anyone tried this ???

What about the problem caused by the bigger gap ??

This one should be fixed with a smal signal ampifier (opamp for example) ?

BTW I am an electronic developer.

I am thinking about this, because tomorrow I will perhaps buy a Caddy STS with a P056 History.....

regards Psycho ;)

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There may be major differences between how the signal is processed in my 1998 vehicle as compared to the vehicle you are referring to. And correct me if I am wrong, but code P056 is the transmission input speed sensor, correct?

For my 1998 Seville, the transmission input speed sensor produces a signal where the voltage (amplitude) is used as a measure of speed of rotation. The higher the input shaft speed, the higher the sensor output voltage.

The control module is not expecting to see a signal where the frequency (pulses per second) varies with speed which is the case with a vehicle speed sensor output.

You might be on to something as a patch, but it will take some redesign and adaptation. Might be easier to open the transmission and replace the faulty sensor.

Jim

Drive your car.

Use your cell phone.

CHOOSE ONE !

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If you are talking about the ISS sensor, I am currently finishing up that job, see it here, Mike

http://caddyinfo.ipbhost.com/index.php?sho...t=0&start=0

Pre-1995 - DTC codes OBD1  >>

1996 and newer - DTC codes OBD2 >> https://www.obd-codes.com/trouble_codes/gm/obd_codes.htm

How to check for codes Caddyinfo How To Technical Archive >> http://www.caddyinfo.com/wordpress/cadillac-how-to-faq/

Cadillac History & Specifications Year by Year  http://www.motorera.com/cadillac/index.htm

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Hi

just for my understanding.

The P056 can have 4 causes:

Electromagnetical coupling - spark, cb.....

Broken axle speed sensor

Defective wiring or connector problem

Gap between sensor and rotor to big (causes smaller signal)

So if the error is present you have to change the sensor.

That means to open the transmission.

But today I thought about a other possibility:

I meassured the signal on PD72 and the input speed Signal was the same, as the engine-rpm.

If this should be so in any driving condition, the problem can be fixed by routing the engine rpm signal to the

input of the transmission rpm.

Has anyone tried this ???

What about the problem caused by the bigger gap ??

This one should be fixed with a smal signal ampifier (opamp for example) ?

BTW I am an electronic developer.

I am thinking about this, because tomorrow I will perhaps buy a Caddy STS with a P056 History.....

regards Psycho ;)

Thats not correct.

The variable voltage is an effect of how the sensor works.

It is a simple magnetic pick-up.

So the higher the frequency (rpm) goes, the higher is the output voltage.

You can calculate this, if you know the inductivity of the coil of the pick-up.

And Mike

yes, i mean that, but I haven't got the time in the moment to open the transmission.

So the circuit, I will build is a temporary solution (but realy good step by step description you made !!)

regrads Eckhard :-)

Psycho.gif

243728.png LPG

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Hi

just for my understanding.

The P056 can have 4 causes:

Electromagnetical coupling - spark, cb.....

Broken axle speed sensor

Defective wiring or connector problem

Gap between sensor and rotor to big (causes smaller signal)

So if the error is present you have to change the sensor.

That means to open the transmission.

But today I thought about a other possibility:

I meassured the signal on PD72 and the input speed Signal was the same, as the engine-rpm.

If this should be so in any driving condition, the problem can be fixed by routing the engine rpm signal to the

input of the transmission rpm.

Has anyone tried this ???

What about the problem caused by the bigger gap ??

This one should be fixed with a smal signal ampifier (opamp for example) ?

BTW I am an electronic developer.

I am thinking about this, because tomorrow I will perhaps buy a Caddy STS with a P056 History.....

regards Psycho ;)

Thats not correct.

The variable voltage is an effect of how the sensor works.

It is a simple magnetic pick-up.

So the higher the frequency (rpm) goes, the higher is the output voltage.

You can calculate this, if you know the inductivity of the coil of the pick-up.

And Mike

yes, i mean that, but I haven't got the time in the moment to open the transmission.

So the circuit, I will build is a temporary solution (but realy good step by step description you made !!)

regrads Eckhard :-)

Eckard, Thanks, I just bought a technician guide for the tranny, I will look it over to see if there is anything in it that can help you. I think, that the ISS sensor triggers a LOW and HIGH condition, but don't quote me yet.

I just realized that we have had three members from Germany active in the last two days, you, Stefank and FSchuett.

I will see what I can find for you, Mike

Pre-1995 - DTC codes OBD1  >>

1996 and newer - DTC codes OBD2 >> https://www.obd-codes.com/trouble_codes/gm/obd_codes.htm

How to check for codes Caddyinfo How To Technical Archive >> http://www.caddyinfo.com/wordpress/cadillac-how-to-faq/

Cadillac History & Specifications Year by Year  http://www.motorera.com/cadillac/index.htm

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Eckhard, here is a description from an ATRA technician's guide, hope this helps

ISSSpeedSensorDescription.jpg

Pre-1995 - DTC codes OBD1  >>

1996 and newer - DTC codes OBD2 >> https://www.obd-codes.com/trouble_codes/gm/obd_codes.htm

How to check for codes Caddyinfo How To Technical Archive >> http://www.caddyinfo.com/wordpress/cadillac-how-to-faq/

Cadillac History & Specifications Year by Year  http://www.motorera.com/cadillac/index.htm

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Someone on this or the "other" forum once posted about his success in constructing a small single op-amp circuit that was able to amplify the weak signal from the defective sensor such that the PCM became happy. I lost the bookmark when my HDD died. Never found it again.

As I recall his design required a double ended power supply, so he powered it off a fibe quietl of AA batteries. Battery life was several months. He mounted it under the dash by the PCM.

If I were to build one I'd use an op-amp that required a single ended power supply. It could then be mounted under the hood and run off +12 volts.

Let us know if you come up with a working design.

Regards,

Warren

EDIT: That should read "fibe quietl of AA batteries." Dunno why I can't edit it.

EDIT: Okay, let's try this: "handful of AA batteries."

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I think I am missunderstood.

I know how the sensor works and I just wanted to know if someone has tested to fake the sensor with the engine RPM data.

To buil a ciruit to amplify the signal is realy cheap work.

1 op tl084, 2 resistors and a few capcitors.

Peanuts.....

regards Eckhard :-)

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