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propnut

Previa Knock Sensor

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My knock sensor has gone bye bye and Toyota list two for this car, one made by Matsu****a and the other Nippondenso. From what I can tell there were no changes to the Previa 2TZFE engine between 1990 - 1997 so am assuming that they are both the same. Does anyone know for sure ??

Thanks

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Ok, never mind I have found the answer for myself. All knock sensors work by detecting frequency ranges of between 5 and 15Khz. Upon detecting them the piezotransducer (basically a little mic) sends a voltage to the ECU. The ECU references the voltage level against programmed parameters which indicate the presence or not of pre-detonation. The ECU then takes the relevant action to advance or !Removed! the timing accordingly.

Now knock sensors are tuned to the the engine that they come out of but it is not actually all that scientific and as long as certain variables match, sensors are interchangeable between engines which are similar as long as the actual fittings are the same (even this is not imperative). As such in the case of the Previa which has a displacement of 2.4l and is a four cylinder arrangement any knock sensor suitable for an engine of the same arrangment and similar capacity will work.

For your information on the Previa's the MIL code that indcates a blown knock sensor is 52. Confirmation that it has actually blown can be had by disconnecting the centre plug from the ECU ( WITH THE IGNITION OFF !!!!!!!!!) and measuring continuity between the corresponding pin on the ECU and earth. If continuity exists the sensor is shot. If there is no continuity and yet the code exists then you have two more choices.

1. If you have an oscilloscope and know how to use it, connect it accordingly to pin 14. Tap the engine with a hammer, if working you will see a corresponding signal. Amplitude and waveform is irrelevant at this stage as all you are checking is that it is producing electrical feedback to the ECU.

2. AS LONG AS YOU ARE COMPENTANT. Cut the wire from the relevant pin MAKING 200% sure that a) you cut the right wire B) you leave enough free cable between the plug and the cut to enable you to resolder and heatshrink the cable again) put the plug back in. Remove the EFI fuse for 30 secs or more to reset the ECU code then replace it. Restart the car if the exact same code returns and the car runs no differently it is the sensor.

Leave the wire cut for now, you can drive the car like this but note that there will be no correction for pinking. Modern fuels have a stable enough Octane rating where it is not really an issue. HOWEVER under heavy load, e.g. foot flat in the wrong gear or loading going up a hill, if you hear pinking either change down a gear or ease off on the throttle.

This is just a temp solution the sensor still needs to be changes.

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Ok, never mind I have found the answer for myself. All knock sensors work by detecting frequency ranges of between 5 and 15Khz. Upon detecting them the piezotransducer (basically a little mic) sends a voltage to the ECU. The ECU references the voltage level against programmed parameters which indicate the presence or not of pre-detonation. The ECU then takes the relevant action to advance or !Removed! the timing accordingly.

Now knock sensors are tuned to the the engine that they come out of but it is not actually all that scientific and as long as certain variables match, sensors are interchangeable between engines which are similar as long as the actual fittings are the same (even this is not imperative). As such in the case of the Previa which has a displacement of 2.4l and is a four cylinder arrangement any knock sensor suitable for an engine of the same arrangment and similar capacity will work.

For your information on the Previa's the MIL code that indcates a blown knock sensor is 52. Confirmation that it has actually blown can be had by disconnecting the centre plug from the ECU ( WITH THE IGNITION OFF !!!!!!!!!) and measuring continuity between the corresponding pin on the ECU and earth. If continuity exists the sensor is shot. If there is no continuity and yet the code exists then you have two more choices.

1. If you have an oscilloscope and know how to use it, connect it accordingly to pin 14. Tap the engine with a hammer, if working you will see a corresponding signal. Amplitude and waveform is irrelevant at this stage as all you are checking is that it is producing electrical feedback to the ECU.

2. AS LONG AS YOU ARE COMPENTANT. Cut the wire from the relevant pin MAKING 200% sure that a) you cut the right wire B) you leave enough free cable between the plug and the cut to enable you to resolder and heatshrink the cable again) put the plug back in. Remove the EFI fuse for 30 secs or more to reset the ECU code then replace it. Restart the car if the exact same code returns and the car runs no differently it is the sensor.

Leave the wire cut for now, you can drive the car like this but note that there will be no correction for pinking. Modern fuels have a stable enough Octane rating where it is not really an issue. HOWEVER under heavy load, e.g. foot flat in the wrong gear or loading going up a hill, if you hear pinking either change down a gear or ease off on the throttle.

This is just a temp solution the sensor still needs to be changes. hi can you tell me please what were your symtoms on the car to tell you your sensor had gone please thanks bob

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Bob

It is easier to see what you have asked if you remove the automatic quote first. I had to read it carefully to finally find your question at the bottom.

The MIL light on the dashboard lit up and an interrogation of the ECU displayed an error code 52 which denotes a failed knock sensor.

In my case it failed due to the engine overheating after the radiator blew. The whole top of the sensor melted off. As I needed to drop the motor to change the sensor I redid the head gasket at the same time. If yours is a high mileage car I would seriously recommend you do the same. It is not a hard job only time consuming.

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Bob

It is easier to see what you have asked if you remove the automatic quote first. I had to read it carefully to finally find your question at the bottom.

The MIL light on the dashboard lit up and an interrogation of the ECU displayed an error code 52 which denotes a failed knock sensor.

In my case it failed due to the engine overheating after the radiator blew. The whole top of the sensor melted off. As I needed to drop the motor to change the sensor I redid the head gasket at the same time. If yours is a high mileage car I would seriously recommend you do the same. It is not a hard job only time consuming.

hi guys can you tell me the symtoms the car had when the knock sensor is faulty thanks for the help

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Let me ask you a question.

Why are you asking this question, Do you believe your knock sensor is gone and if so why ???

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Let me ask you a question.

Why are you asking this question, Do you believe your knock sensor is gone and if so why ???

well my car stall's once it's warm i cleaned and checked the throttle body/fuel filter /replaced front lambda sensor but after i drive a few hundred yards it feels as there is no fuel getting through,it will pick up again then swamp not sure what else i can do to solve problem,thats why i was asking about knock sensor my mielage is 180,000

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Ok so let me put your mind at rest, from what you have said it is definitely NOT your knock sensor. You could have anything from worn/dirty injectors to low compressions to something as simple as a blocked fuel filter.

How often is the car serviced, are all the filters new, have the plugs been changed are you using Oil, does the car smoke .

Sorry but there is no easy answer to your problem it really needs to be analysed in the flesh as it were.

A knock sensor detects pre-detonation of fuel or as the name suggests knocking. This is when the fuel ignites before the point at which it should. The engine is then forced to work against the combustion which results in a high frequency knock. This knock is detected by the knock sensor and a signal sent to the ECU which in turn retards the timing to overcome the problem.

Most people know knock as pinking, when you accelerate really hard you get a noise like marbles rattling in your engine.

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Ok so let me put your mind at rest, from what you have said it is definitely NOT your knock sensor. You could have anything from worn/dirty injectors to low compressions to something as simple as a blocked fuel filter.

How often is the car serviced, are all the filters new, have the plugs been changed are you using oil, does the car smoke .

Sorry but there is no easy answer to your problem it really needs to be analysed in the flesh as it were.

A knock sensor detects pre-detonation of fuel or as the name suggests knocking. This is when the fuel ignites before the point at which it should. The engine is then forced to work against the combustion which results in a high frequency knock. This knock is detected by the knock sensor and a signal sent to the ECU which in turn retards the timing to overcome the problem.

Most people know knock as pinking, when you accelerate really hard you get a noise like marbles rattling in your engine.

hi thanks for the reply,ive changed the spark plugs /the front lambda sensor the fuel filter is bringing fuel up to the fuel rail,so i assume the filter is ok ive also changed the maff sensor/the air filter/ checked for fuel pressure pcv valve,also egr valve so im stumped now,it doesnt use Oil and doesnt smoke at back it tick's over fine just when you try to drive away it swamps then picks up then dies again

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Ok so the problem is without actually seeing the car I doubt anyone is going to be able to give you a prognosis.

HOWEVER as the problem seems to be temp related you could check a few more things

Under the drivers seat there are 2 sensors one above and one below the temp sender unit. One has a green head and is the temp sensor that sends info to the ECU about the engine temp. The other with a grey plug is the cold start injector time switch. Test both of these as outlined in this workshop manual

http://www.autozone.com/az/cds/en_us/09008...irInfoPages.htm

The manual covers all other diagnostics as well so also check things like your MAF sensor.

The other thing to be aware of is that at 180K you are pretty much overdue for a blown head gasket and as your problem starts to occur when the engine is warm start looking for the tell tale signs e.g. losing water in the expansion bottle, steam coming from the exhaust. engine running hotter than usual etc. The swamping may not be from fuel but water getting into the combustion chamber.

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On 6/27/2007 at 8:46 PM, propnut said:

My knock sensor has gone bye bye and Toyota list two for this car, one made by Matsu****a and the other Nippondenso. From what I can tell there were no changes to the Previa 2TZFE engine between 1990 - 1997 so am assuming that they are both the same. Does anyone know for sure ??

Thanks

 

On 6/27/2007 at 8:46 PM, propnut said:

My knock sensor has gone bye bye and Toyota list two for this car, one made by Matsu****a and the other Nippondenso. From what I can tell there were no changes to the Previa 2TZFE engine between 1990 - 1997 so am assuming that they are both the same. Does anyone know for sure ??

Thanks

 

On 12/15/2007 at 2:53 PM, bobnick said:

hi thanks for the reply,ive changed the spark plugs /the front lambda sensor the fuel filter is bringing fuel up to the fuel rail,so i assume the filter is ok ive also changed the maff sensor/the air filter/ checked for fuel pressure pcv valve,also egr valve so im stumped now,it doesnt use Oil and doesnt smoke at back it tick's over fine just when you try to drive away it swamps then picks up then dies again

Hi Guys

pretty easy to fix this sensor:

1. drill a hole 50mm diameter 10cm from the opening edge under the passenger seat.

2. use 27mm long socet to release the broken unit.

3. use magnet to pull it out

4. cut the side as shown in the pics

5. solder thin wire to the underside of the pirzo plate

6. solder the connector pin after shortening it

7. cover with epoxy cement

8. reassemble

good luck

Avi Ofek

 

 

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IMG_20200216_144649.jpg

IMG_20200216_150858.jpg

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Hopefully the op has fixed their car by now or it's been scrapped as this thread is 12+ years old !!!!

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