How to test the Crank Angle 1 & 2 and Cam Angle Sensor.

[Dessertrunner]

A number of cars are getting a bit of age on them and some are developing new problems such as the 3 sesnors for the angles. I want to find a way to find out which one is giving problems. What happens is that often the ECU can't pick up a code. I had a bad crank angle sensor on my car but never got a code. My wifes car failed to start on cold mornings and it did get a code, (code 29 Crank Angle Sensor). I am working through the suggest methods in the manual but so far none have helped. Any suggests would be greatly appricated.
Tony

[Crazy_pilot]

Perhaps the signal can be measured directly from the sensor to see if it's within spec? Connect multimeter and either turn the motor manually or crank with the starter and verify that the numbers are reading correctly.

[SVXRide]

My understanding is that you can only check them with an oscilloscope (have to look at their waveform). I really hope someone does figure out an easier way.
-Bill (who just had to replace a crank sensor on his Pearlie because it wouldn't start...)

[Elaine]

The Crank Angle and Cam angle are coils that generate a voltage pulse when the magnetic field in their proximity changes. You have several ways to check them. The simplest one, take a multimeter and measure their resistance. If you see something close to 2.4 Kohm they are OK most likely. If you are there I would suggest to measure the resistance you can see at the harness connector pins. It should be around 90Kohm if I have a good memory. This will prove that the ECU is accessible from the Sensor harness connector.
The more complex way of testing it is with an oscilloscope. If you have one just let me know and I can email you the procedure described in the Subaru Service Manual.

[Dessertrunner]

I have a copy of the manual and am working my way through what it suggests. I have 2 sensors that are bad to try and see if I can distingish them from a good one. I am going the try and make a harness to plug between the ECU and the engine fitted in the engine bay, in that way I can run test with the engine going. Will keep ypu posted.
Tony

[Elaine]

Tony,
The signal generated by the angle sensor crosses two connectors, the harness cable and the input stage of the ECU. If any of these fails the behavior of the car will be virtually the same. Moreover, there is no moving part in this chain, the signal generated by the sensor is not extreme and the sensor itself is quite simple. From this perspective the probability to have a bad sensor rather than a bad ECU for instance shouldn't be much higher... The only problem with the sensor is probably the fact that it's always in a high temperature environment.

[SVXRide]

I'm trying to remember, but aren't the crank and cam sensors basically Hall effect devices?
-Bill

[SVXRide]

Found it (thank you, Wiki :rolleyes:)

Commonly used in distributors for ignition timing (and in some types of crank and camshaft position sensors for injection pulse timing, speed sensing, etc.) the Hall effect sensor is used as a direct replacement for the mechanical breaker points used in earlier automotive applications. Its use as an ignition timing device in various distributor types is as follows. A stationary permanent magnet and semiconductor Hall effect chip are mounted next to each other separated by an air gap, forming the Hall effect sensor. A metal rotor consisting of windows and tabs is mounted to a shaft and arranged so that during shaft rotation, the windows and tabs pass though the air gap between the permanent magnet and semiconductor Hall chip. This effectively shields and exposes the Hall chip to the permanent magnet's field respective to whether a tab or window is passing though the Hall sensor. For ignition timing purposes, the metal rotor will have a number of equal-sized tabs and windows matching the number of engine cylinders. This produces a uniform square wave output since the on/off (shielding and exposure) time is equal. This signal is used by the engine computer or ECU to control ignition timing. It is worth noting that many automotive Hall effect sensors have a built-in internal NPN transistor with an open collector and grounded emitter, meaning that rather than a voltage being produced at the Hall sensor signal output wire, the transistor is turned on providing a circuit to ground though the signal output wire.

[Elaine]

Nope, it's not a Hall effect sensor. The SVX one is coil based. There is a clear diagram in the Manual.

[oab_au]

I have a copy of the manual and am working my way through what it suggests. I have 2 sensors that are bad to try and see if I can distingish them from a good one. I am going the try and make a harness to plug between the ECU and the engine fitted in the engine bay, in that way I can run test with the engine going. Will keep ypu posted.
Tony

Hi Tony, wife still talking to you?:)

You can only really test those sensors with a scope. The lesser way is to use a good digital multi meter to measure the out put of the sensor in AC voltage, less than 5V.

The usually they go out is for the magnet in the sensor to lose its magnetic flux. This reduces over the years due to heat and vibration, so that at low rpm the output is low, at cranking speed, it is too low to read.

Harvey.

[Dessertrunner]

I am building a harness to plug between the ECU and the Engine so I can get test points to use the scope. The first one will let me test the 3 angle sensors, the 2 knock sensors and the 2 temp guages. Here is a photo of the two plugs I am going to use. Once this test harness is built I should be able to get an understanding of what a bad sensor looks like.
Tony

[Dessertrunner]

Here are a couple of shots of the adapter. I tested it on the car before I tap in the new feed wires to run to the test gear. Car started etc with out a problem. Hope in the next couple of hours to get the rest of the harness built.
Tony

[Dessertrunner]

Finished the cable now need to plug in so I can put the scope on the sensors.
Tony

[TomsSVX]

I noticed you said that the wife's car was a hard start... Often the CTS can go bad causing hard starting. When this happens the Crank angle sensor often pops up as a fault because the engine is turning over but not starting... Let us know your findings with the new harness:)

Tom

[Dessertrunner]

Tom what do you mean by CTS, sorry to be so dumb? Also it wouldn't start on really cold mornings when the car temp went below 0C.
Tony

[Hocrest]

Tom what do you mean by CTS, sorry to be so dumb? Also it wouldn't start on really cold mornings when the car temp went below 0C.
Tony
He meant Coolant Temperature Sensor.

Sounds right...

[Dessertrunner]

Here is the scope image of a good cam sensor plan to change to a bad one and see if anything shows up.
Tony

[AUSVX]

Hey I'm also having no luck finding which sensor in the car isn't working properly... I check codes regularly but nothing.


1----
Twice in the last 9 months I have started the car in the morning and everything is perfect and about 2 minutes into driving the engine vibrates like crazy, revving it feels like it's going to ruin the engine. I stop and start the engine and it's still there.... After a few start and stops everything is perfect again. (I've read something once about one side of the engine shutting down is this related?)

2----
If I start the car in the morning everything is perfect.
If I turn off the car after completely warmed up and start it straight away it's perfect.
If I turn off the car and come back 2 hours later and start the car the engine keeps on turning over and over and eventually starts.

Any suggestions?
Have changed coolant temp sensor and gauge temp sensor (the one just above the coolant temp sensor. After installing them a few months ago I disconnected the battery.. left it disconnected overnight to reset everything

Thanks, Jordan.

[mysvxrocks]

I had one of those sensors go bad on my 92. The car wouldnt start, period. I picked up all three out of a wrecking yard car, put them all in, and it started right up. I have no idea which one was bad.... Codes said two of them were. I priced them new, and omg... $250 a piece, if you can even find one... So stupid...

[Dessertrunner]

Jordan
Did you ask Brooky, two of the sensors are the same so if you get one you can swap them over. My guess is the cam sensor near the battery.
Tony

[AUSVX]

Hey I didn't ask brooky because both cars had no engines and wiring harnesses... I just assumed they had been bought by someone else already, might still be worth giving them a call

Are the cam and crank sensors shared with any other Subaru?

Thanks for the help guys!!!!!

[oab_au]

Hey I didn't ask brooky because both cars had no engines and wiring harnesses... I just assumed they had been bought by someone else already, might still be worth giving them a call

Are the cam and crank sensors shared with any other Subaru?

Thanks for the help guys!!!!!

The cam and one of the crank sensors are the same as the Liberty units, the other crank sensor is SVX only.

Harvey.

[Dessertrunner]

Okay finished the testing to see if a difference appeared on a bad crank or cam sensor showed up on a scope. The good news is it does. What happens is the sensor still sends a signal but wave pattern is not were it should be as regards timing. I also sprayed freeze spray on the sensor when it was cold and the wave form moved out of aligment. If you have a look at the two images you will see one is clean and the other has a ghost wave, it is the bad sensor.

[SVXRide]

So, you've confirmed that a 'scope is mandatory to determine if the crank angle and cam angle sensor are bad (?)
-Bill

[Dessertrunner]

yes. The scope can pick up the problem when the ECU doesn't. Also you can test the knock sensors. Its surprising how bad the signal can be and the car shows no major signs.
Tony

[XT6Wagon]

Hey I'm also having no luck finding which sensor in the car isn't working properly... I check codes regularly but nothing.


1----
Twice in the last 9 months I have started the car in the morning and everything is perfect and about 2 minutes into driving the engine vibrates like crazy, revving it feels like it's going to ruin the engine. I stop and start the engine and it's still there.... After a few start and stops everything is perfect again. (I've read something once about one side of the engine shutting down is this related?)

2----
If I start the car in the morning everything is perfect.
If I turn off the car after completely warmed up and start it straight away it's perfect.
If I turn off the car and come back 2 hours later and start the car the engine keeps on turning over and over and eventually starts.

Any suggestions?
Have changed coolant temp sensor and gauge temp sensor (the one just above the coolant temp sensor. After installing them a few months ago I disconnected the battery.. left it disconnected overnight to reset everything

Thanks, Jordan.

Check your battery cables for corrosion. The negative cable on mine had the body ground mounting point corroded to the point nothing much passed. The battery end of both cables were terrible too. I think the sensors start to read really screwy when you say have a .5 V drop from the engine/ecu to the battery on the negative side. More so since corroded cables will have a non-linear response to increased load.

This will give you a clean baseline to start with on your sensors and infact checking the ECU ground seems to be Subarus #1 thing to recomend in troubleshooting anything dealing with the engine

[AUSVX]

Hey thanks a lot for the tip im looking into that, I really wouldn't be suprised if that's what it is as well as crank and cam angle sensors.

Jordan.