Black comedy of errors:ECU/sensor problem

[DTL]

Hi all,

This is a continuation of my previous thread about my 2.2 legacy burning xistors/ignitors.

 

What a disaster, I have replaced the ECU twice, first time, it was not the ecu, it was the computer for the AWD LOL... I took a ride yesterday and got the right ECU from a junkyard in queens, plugged it in and .... no start.

 

I am getting spark from the coil for #1/#2, but not #3/#4. The ignitor is not switching.

I looked at the old ECU output by dragging my Digital storage scope out of the basement (something I will not do unless I am desperate). The ECU signal seemed probably ok for the 1/2 plugs but there was a much smaller signal for the 3/4 plugs AND it was IN SYNC with the 1/2 pair. I figured I found my problem, bad ECU and this new one would fix the problem. I figured I was seeing some crosstalk through the ignitor that is not enough to switch it. In fact I measured a base-emmiter voltage drop from either ignitor input to the both ignitor outputs, base 1 to emitter 1 and base 2 to emitter 2 were both like .7 volts-.8 volts , base 1 to emitter 2 and base 2 to emmiter 1 was almost double that. <b>This is true on both the ignitors I have so, I guess it is part of the desgn, and the ignitors are both good.. am I wrong?</b>

 

Anyway, I used just my DMM today when it did not start and found still only a funky low voltage change for the 3/4 output signal. Made me think the connector cable for 3/4 must be open and I am looking at a floating voltage.

after MUCH screwing around testing the cable andplaying with the connector while hanging uncomfortably nearly upside down, it seems all that every thing is good.

Yesterday I also took the liberty of stipping some wire off the cam and crank sensor to get a scope peak at what they were doing and much to my dismay, they seems to be producing good signals:

at cranking sppeed the CAM sensor put out about 12 AC pulses in 2 seconds.from .5 to 1 volt. The crank sensor put out groups of AC pulses in a roughly sinusoidal envelope varying between roughly .5 volt to 2 volts, from what I remember. These pulses were spaced roughly 20 to 30 msec in groups of 3, repeating roughly every 160 msec, they did seem a bit noisier than the cam sensor..

 

??????????????????

 

I am at a loss, all I can think is that one of the sensors is screwing things up for the ECU, there is no chance both ECUs would fail in the same way.(?)!

I am getting a knock sensor error...will that do it? the knock sesor is reading only 1/10 ohms as it should (5.7k). This new ECU is reporting a TPS error too, is that possibly left over from the previous vehicle, I was not getting that with the old ECU? I couldn't clear the errorcodes for some reason, did something wrong I guess.

 

help, this is driving me up a tree.

 

 

 

 

 

 

 

 

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[porcupine73]

Did you say you checked the coil pack? What do you get if the ignitor is unhooked from the coil pack?

[DTL]

Did you say you checked the coil pack? What do you get if the ignitor is unhooked from the coil pack?

 

 

replaced coil pack .... about .8 ohms primary for both about 15k secondary for both.

[Cougar]

The crank sensor put out groups of AC pulses in a roughly sinusoidal envelope varying between roughly .5 volt to 2 volts, from what I remember. These pulses were spaced roughly 20 to 30 msec in groups of 3, repeating roughly every 160 msec, they did seem a bit noisier than the cam sensor...

 

It sounds to me that you are only seeing some ringing pulses from the sensor. I think the crank sensor may be bad.

 

Did you look at the ECU output signals on pins 9 and 10 of the ECU to the ignitior using your scope and compare them?

[DTL]

It sounds to me that you are only seeing some ringing pulses from the sensor. I think the crank sensor may be bad.

 

Did you look at the ECU output signals on pins 9 and 10 of the ECU to the ignitior using your scope and compare them?

 

Hi Cougar

Yes. As I wrote in my post:

 

"I am getting spark from the coil for #1/#2, but not #3/#4. The ignitor is not switching.

I looked at the old ECU output by dragging my Digital storage scope out of the basement (something I will not do unless I am desperate). The ECU signal seemed probably ok for the 1/2 plugs but there was a much smaller signal for the 3/4 plugs AND it was IN SYNC with the 1/2 pair. I figured I found my problem, bad ECU and this new one would fix the problem. I figured I was seeing some crosstalk through the ignitor that is not enough to switch it. In fact I measured a base-emmiter voltage drop from either ignitor input to the both ignitor outputs, base 1 to emitter 1 and base 2 to emitter 2 were both like .7 volts-.8 volts , base 1 to emitter 2 and base 2 to emmiter 1 was almost double that. <b>This is true on both the ignitors I have so, I guess it is part of the desgn, and the ignitors are both good.. am I wrong?</b>"

 

I looked at pins 9 and 10 at the ignitor.

 

My question is really this:

Under what conditions will the ECU only fire the 1/2 coil? ( I forget whether that is pin 9 or 10).

There was a new timing belt put into this car about 2 months before it rolled over and played dead. Can a 10 thumbed mechanic screw up the cam sensor enough to do that?

As far as what my scope saw, the crank sensor signal was noisier and funkier.

 

Also, are the crank and cam sensors the only ones that will stop the ecu from firing?... I think I need the wisdom of a SubaGuru here.

[porcupine73]

Sorry I wasn't sure, did you check the outputs from the ECU to the ignitor without it being connected to the ignitor? Like if there is a short in there or something it might be presenting too much load to the ECU. Not sure, are the outputs from the ECU just like open collector outputs or does it give +5V or something?

 

Does your crankshaft position signal look like this? They don't say what the amplitude should be though...

[porcupine73]

Also does your camshaft position sensor signal look like this? You said the timing belt was replaced - AFIAK if it is even two teeth off the vehicle will not start; not sure if it would still spark all signals if it is two or more teeth off though...ECU does know a tolerance for agreement of camshaft and crankshaft positions.

[DTL]

Sorry I wasn't sure, did you check the outputs from the ECU to the ignitor without it being connected to the ignitor? Like if there is a short in there or something it might be presenting too much load to the ECU. Not sure, are the outputs from the ECU just like open collector outputs or does it give +5V or something?

 

Does your crankshaft position signal look like this? They don't say what the amplitude should be though...

 

Yes, Crankshaft sensor output was very close to that.

 

As far as the ECU output goes. When I scoped the first ECU got what I thought was a normal output for 1/2 coil/ channel. The other one was insync instead of off set in time, it was less than .7 volts .... I think I looked at it loaded to the ignitor. I captured 2 channel 5 sec sample with my scope but the humidity started to make my scope act flakey, dropping out a channel w/o me touching the scope! so, I got flustered an brought it make onto the house! But the "new" ECU i bought 2 days ago acted roughly the same: 1/2 firing , 3/4 not....- my DMM jumped around 0 to 3+ volts for the 1/2 out put, the 3/4 output averaged under a volt.

Maybe I will take my scope out again later today.

What is the chance that 2 ECUs could have the same problem....small I would say, thats why I focused on the signal paths. but they check out ok, isolated from each other and continuous from connector to connector.

...its getting nuts, maybe one connector contact is bending away when you push it in.... I will try giving them a twist bend a bit later.

 

I suppose I need to make sure the signal paths for the sensors are continuous.

 

<b>I would like to see a flowchart describing the how the ECU uses the sensors.</b>

 

Thanks porcupine

[DTL]

Also does your camshaft position sensor signal look like this? You said the timing belt was replaced - AFIAK if it is even two teeth off the vehicle will not start; not sure if it would still spark all signals if it is two or more teeth off though...ECU does know a tolerance for agreement of camshaft and crankshaft positions.

 

 

Hmm, I will have to re-scope that.

I counted roughly 12 more or less equal and evenly spaced pulses in 2 sec. They could have been pulse groups, I will recheck with a shorter time base.

 

when normally starting about how fast does the engine rotate? 1 rev per 1 or 1 seconds?

[porcupine73]

I think crank speed is about 300rpm. Is this ignition system schematic from the manual helpful? Also some other stuff from the service manual....not sure if it is helpful:

CHECK COIL "+" TERMINAL VOLTAGE

With ignition "ON," measure voltage between coil "+" terminal (E10)2 and ground. It should read 10V minimum .

 

CHECK COIL RESISTANCE

Ignition Coil Testing

 

Disconnect coil connector and remove coil from engine.

Measure resistance of coil primary and secondary windings as follows: PRIMARY Connector

& terminal: Resistance:

(E10)2 - (E10)1 0.7 Ohm

(E10)2 - (E10)3 0.7 Ohm

 

SECONDARY

 

Terminal: Resistance:

#1 - #2 13.8K Ohms (Hitachi), 21K Ohms (Diamond)

#3 - #4 13.8K Ohms (Hitachi), 21K Ohms (Diamond)

 

CHECK IGNITOR INPUT SIGNAL

Igniter Testing

 

While cranking engine, check that voltage varies synchronously with engine revolutions at ignitor connector terminals (B8)1 and (B8)2.

 

CHECK HARNESS BETWEEN ECU AND IGNITOR

 

Disconnect ECU and ignitor connectors.

Check resistance between ECU and ignitor connectors and ground as follows: Connector

& terminal: Resistance:

(F47)9 - (B8)2 0 Ohms

(F47)10 - (B8)1 0 Ohms

(F47)15 - (B8)3 0 Ohms

(B8)3 - Ground 0 Ohms

(B8)1 - Ground 1M Ohms min.

(B8)2 - Ground 1M Ohms min.

[Cougar]

First let me say hats off to Porcupine73 for the thumbnails of the prints. This makes things so much easier to talk about.

 

Your comment about the voltage difference between the output leads of the ECU (9 & 10) is concerning to me. I am wondering if the ignitor is loading the circuit down or there is a probem with the ECU output to it. We need to find out which way to look for the problem. Since you have a scope to look at this I would recommend you isolate the ignitor input connection and place a load resistor (1000 ohms) on each of the two leads and connect the other ends of the resistors to ground. Then check the signals across each of the resistor leads and compare them. They should be the same. If they are, then we need to check further down the line for a problem. If the output signal for 3 and 4 is down then I would look at the CAS cog. One of the cogs may have broken off.

[DTL]

I think crank speed is about 300rpm. Is this ignition system schematic from the manual helpful? Also some other stuff from the service manual....not sure if it is helpful:

CHECK COIL "+" TERMINAL VOLTAGE

With ignition "ON," measure voltage between coil "+" terminal (E10)2 and ground. It should read 10V minimum .

 

CHECK COIL RESISTANCE

Ignition Coil Testing

 

Disconnect coil connector and remove coil from engine.

Measure resistance of coil primary and secondary windings as follows: PRIMARY Connector

& terminal: Resistance:

(E10)2 - (E10)1 0.7 Ohm

(E10)2 - (E10)3 0.7 Ohm

 

SECONDARY

 

Terminal: Resistance:

#1 - #2 13.8K Ohms (Hitachi), 21K Ohms (Diamond)

#3 - #4 13.8K Ohms (Hitachi), 21K Ohms (Diamond)

 

CHECK IGNITOR INPUT SIGNAL

Igniter Testing

 

While cranking engine, check that voltage varies synchronously with engine revolutions at ignitor connector terminals (B8)1 and (B8)2.

 

CHECK HARNESS BETWEEN ECU AND IGNITOR

 

Disconnect ECU and ignitor connectors.

Check resistance between ECU and ignitor connectors and ground as follows: Connector

& terminal: Resistance:

(F47)9 - (B8)2 0 Ohms

(F47)10 - (B8)1 0 Ohms

(F47)15 - (B8)3 0 Ohms

(B8)3 - Ground 0 Ohms

(B8)1 - Ground 1M Ohms min.

(B8)2 - Ground 1M Ohms min.

 

 

Thanks Porcupine.

 

I printed that schematic a couple weeks ago and have it almost committed to memory!

the ignitor is getting a bad signal for the 3/4 coil.

Either, the sensors is giving the ECU bad info, or, .... nothing AFAIK (new acronym for me). I have pretty much gave up on the idea that supernatural forces intervene in between the time I test the connector and the time i plug it in.

 

I am guessing maybe bad sensor or sensor conections, I just wish I knew a touch more about how the ECU processes the cam and crank sensor info, allso a confirmation that those are the only sensors that would have an effect on spark generation.

 

Bill

[Cougar]

I am guessing maybe bad sensor or sensor conections, I just wish I knew a touch more about how the ECU processes the cam and crank sensor info, allso a confirmation that those are the only sensors that would have an effect on spark generation.

 

Bill

 

They are the only two sensors that will be related to this problem. I suspect the cog for the crank sensor has a broken tip. Your scope should show this up if that is the case. Part of the waveform will be missing or distorted.

[nipper]

Thanks Porcupine.

 

I printed that schematic a couple weeks ago and have it almost committed to memory!

the ignitor is getting a bad signal for the 3/4 coil.

Either, the sensors is giving the ECU bad info, or, .... nothing AFAIK (new acronym for me). I have pretty much gave up on the idea that supernatural forces intervene in between the time I test the connector and the time i plug it in.

 

I am guessing maybe bad sensor or sensor conections, I just wish I knew a touch more about how the ECU processes the cam and crank sensor info, allso a confirmation that those are the only sensors that would have an effect on spark generation.

 

Bill

 

Crank position sensor is what determins piston position and identifies where any given piston is at any given time. A failed crank sensor will give you a no start condition.

 

Camshaft position sensor has more to do with the timing of the fuel injectors. A failed cam sensor will not affect the starting of the car, but will screw up the injector timing.

 

Other sensors come into the picture as far as adjusting the timing, including the knock sensor, map, o2 and engine temp. The only sensor that will keep the car from starting (sometimes) in that list is the ECU Engine Temp sensor.

 

When you test the cam and crank sensors, it is important to test them by hand spinng the engine and looking for minor AC fluxuations that properly spaced (look in the haynes manual) and of a consistant output. You may have a damaged tooth on the cam wheel.

 

nipper

[DTL]

They are the only two sensors that will be related to this problem. I suspect the cog for the crank sensor has a broken tip. Your scope should show this up if that is the case. Part of the waveform will be missing or distorted.

 

Alrighty then,

 

I just tracked the wire for the cam sensor, There are 3 and they all go to the ecu ( red, black and white) unlike what my chilton shows (2 connect(black and white) and one is a shield (yellow))

I get diodes connecting the red and the white in the sensor in both directions with a .47 voltage drop.

I am guessing this is some sort of optical sensor?

 

anyways, I like the crank sensor theory.... let me look into what to do about it.

[nipper]

Alrighty then,

 

I just tracked the wire for the cam sensor, There are 3 and they all go to the ecu ( red, black and white) unlike what my chilton shows (2 connect(black and white) and one is a shield (yellow))

I get diodes connecting the red and the white in the sensor in both directions with a .47 voltage drop.

I am guessing this is some sort of optical sensor?

 

anyways, I like the crank sensor theory.... let me look into what to do about it.

 

Cam crank (and vss) sesnors are all hall effect sensors (magnetic), not optical. Haynes is showing only black, yellow and white, with yellow being the sheild. i lost track of the year of your car, but 1996 and on they show only two wires.

 

nipper

[Cougar]

Use your scope to look at the crank sensor signal and compare the waveform to the thumbnail picture that Porcupine73 posted. My bet is one of the six pulses will be missing or distored, indicating a broken tip.

 

There could be a problem with the CAM sensor instead of the CPS sensor but it is less likely I believe.

[hankosolder2]

Wow, I really hope you figure this one out just to satisfy our curiosity. This might seem low tech, but physically inspecting the timing belt and the teeth for the crank/cam sensors might be easier and more definitive than trying to deductively reason based on the waveforms. Who knows what might be floating around inside the timing belt covers?

 

Nathan

[porcupine73]

Well that is a good point: assuming that the crank angle/position sensor is in good shape, isn't dirty, and doesn't have an excessively large air gap to the crank sprocket nubs.

[DTL]

Cam crank (and vss) sesnors are all hall effect sensors (magnetic), not optical. Haynes is showing only black, yellow and white, with yellow being the sheild. i lost track of the year of your car, but 1996 and on they show only two wires.

 

nipper

I SWEAR there is a black white and a red and they ALL connect to the ECU.

 

The littlest connector, 3 pins in a row, not sure of pin numbers.

 

But my favorite theory is the crank sesnsor, mostly because it looks easier to change out.

[DTL]

Wow, I really hope you figure this one out just to satisfy our curiosity. This might seem low tech, but physically inspecting the timing belt and the teeth for the crank/cam sensors might be easier and more definitive than trying to deductively reason based on the waveforms. Who knows what might be floating around inside the timing belt covers?

 

Nathan

 

y'know there was a sinusoidal envelope to the CAS waveform, that has to be wrong. Each tab should present the same change in reluctance , NO?

 

I will check in tomorow, there is more to life than this F@#$^&*()_cking subaru.

[nipper]

I SWEAR there is a black white and a red and they ALL connect to the ECU.

 

The littlest connector, 3 pins in a row, not sure of pin numbers.

 

But my favorite theory is the crank sesnsor, mostly because it looks easier to change out.

 

After what i just went through with the factory oil pressure, oil temp gauges i beleive you.

i forgot how much i sometimes hate japanese car wiring. Dont get me wrong, its robust, but the wires change colors without warning.

 

 

nipper

[Cougar]

But my favorite theory is the crank sesnsor, mostly because it looks easier to change out.

 

Just in case you may be misunderstanding what we are trying to say about the CPS let me say this. If the CPS cog is the piece that is damaged then this is different than the sensor itself. I think the sensor is fine. It is the cog mounted on the crank that I think may be damaged. This is the piece that rotates and the sensor picks up magnetically as it travels by the sensor itself. It may also be called a reluctor I believe.

[Cougar]

Here is a link to a good picture of the cog mounted on the end of the crank. Courtesy of Legacy777. In the photo you can clearly see 4 of the 6 tabs that go by the sensor, also in the picture.

 

http://www.main.experiencetherave.com:8080/subaru/images/ej22t/20/DCP_4984.JPG

[DTL]

Here is a link to a good picture of the cog mounted on the end of the crank. Courtesy of Legacy777. In the photo you can clearly see 4 of the 6 tabs that go by the sensor, also in the picture.

 

http://www.main.experiencetherave.com:8080/subaru/images/ej22t/20/DCP_4984.JPG

 

 

 

Hey!

 

Great pic.....but it bothers me because corrosion is not a huge issue with this car...how could those metal tabs break or wear off?

it has 180k miles...still they look pretty beefy.

I need a gear puller to get to it?

 

hopefully, I can get to it later today.

Bill