1994 Old 98

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#1
Hey guys,
Thanks for the information regarding the correct obd tool to use in order to get my trouble codes. I now know DTC P0341 is the problem that I am looking at. If I understand this code correctly it is indication that my problem is either the crank sensor or the cam sensor. Is this correct and if you had to guess, which one would you think is the problem with a car thta stalls out from time to time. After it stalls it is sometimes hard to get restarted but it so far has not failed to restart. Are there any specific test you would recommend I do before replacing one or both of these sensors.
Thanks, Jim
 

Gus

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#2
P0341 is for the cam sensor....thing to remember is, you don't need the cam sensor to be fuctioning for the vehicle to start.......it will start with a one in six chance that the injectors are firing at the correct time(PCM "makes" a guess, when it doesn't receive a signal)....this could cause your vehicle to run rough or stall.....

One error some techs make, along with DIY'ers, is let's replace the sensor, when this code happens....while you might "luck out", there are many things that can cause this problem.....

Let's start at the sensor.....there is a magnet that is on the cam.....when it rotates past the sensor, it pulls the output of the sensor down to zero...after it passes, the signal goes aback to 7 volts.....if the magnet is missing, the signal won't change, and the code sets....

It could be a bad sensor.....could be a bad connection at the sensor.......could be a bad harness between the sensor and the ICM......could be a bad connection at the ICM(a car this old, probably had at some point in it's lifetime, someone probe the connector with an improper tool, causing this problem over time).......could be a bad ICM.........could be bad wiring between the ICM and the PCM.....so as you see, without proper testing, it's easy to misdiagnose...

This can be diagnosed with a multimeter....but you need the trouble tree to follow....manuals can be found in large libraries.......even go to a dealership, and make copies of the pages you need......should expect to pay a slight fee for the copied product.....
 
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#3
These sensors are just a random wound magnet wire on a small permanent magnet core embedded in epoxy. Checking the resistance would never tell if you have a dreaded single shorted turn. To properly test them, require an oscilloscope for the proper waveform under load. Only one shorted turn would eat up that output signal.

But for some strange reason, the guys that write these manuals never even heard of an oscilloscope, even though they have been around since the early 20's, that is like 90 years ago.

Never had this problem with ignition points, they never got beyond that stage. Ha, solid state, do not test, replace with a known good part. But how do you know if a part is good when they delete all the specifications for testing that part in their manuals. Engineering gives them all that information!

Scanners are generally only good for checking an open or a short, with most shorts, get smoke or blown fuses, so generally an open. Not exactly working on an F-22 with real diagnostic information based on references. A part can be way out of tolerance and still show good on a scanner. But told even though your vehicle doesn't run worth a damn, nothing is wrong, no codes.

Just replace it with a known good part.
 

Gus

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#4
Well, Nick, if an oscilloscope was part of the diagnosis, I guess every shop would have to get one......I remember the "Cams" machine of the '80's....this was not a required tool, but GM was pushing it for all their dealerships(the price was out of sight)......

It was a 400 pound behemoth, with about a gazillian harnesses that went with it.....but for the price, it only could hook up to GM vehicles....one day a group(Women, no less), came in to demonstrate it......I had a problem car(LeSabre that stalled), that I knew what the problem was, and had diagnosed it in about 5 minutes......between getting the right harnesses, hooking up and starting the machine, finding the right menus, it was 45 minutes later, and they still hadn't found the problem......then they said, the beauty of this is, if you can find the problem solution with this machine, you can transmit live data to engineers in Detroit, to help you solve the problem......"Would you like us to send the data to Detroit?".....by now, this demo had been going on for an hour and a half, for the owner and me and another tech....Owner asked me what I thought.......I started the car, took a long extension, and tapped the pedestal of the crank sensor, and the car stalled.....I said I know what it is.....we didn't get the machine....

In this case, a simple multimeter can test out this circuit, up to the ICM.......

As for points(''Never had this problem with ignition points, they never got beyond that stage."), since when? They would burn all the time, need to be adjusted, the condenser could cause early failure......
 
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#5
Was referring to a small portable 12V operated Tektronix scope I use, only good to 20 MHz, anywhere from 1 millivolt to 100V per vertical division.

Those Snap-On, Allen, Marquette, Sun, etc., huge consoles were just for show to impress ignorant customers. The scopes they had were actually off the shelve TV sets with the tuners removed and a direct connection to the video drivers. Used a capacitance probe to show the spark line and was as accurate as doing surveying work with a rubber band tape measure.

VW also was a bad joke with their analyser, 55 pin connector only had four wires on it for tach, dwell, battery voltage, and ground, the other tests were all conducted manually. Like pulling the back seat out removing the battery cover, then removing each battery cap when they had those and looking in the hole to learn if the electrolyte was low or not. Course the tech doing 99 out of 103 tests could just key in, this or that was bad. Did give an impressive printout to prove to the customer, their VW needed a ton of work.

I was not impressed.

In designing this stuff, we had literally tons of test equipment, not going to list all of that, but for checking MAP sensors, O2 sensors, quadrature waveforms used extensively for stepping motors, pulsed circuits like the CAS, primary inputs into a coil, a small scope is really quite handy and conclusive.

Try it, you may like it. Would even be nice if they printed out the waveform by each I/0.
 

mony0_8

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#6
The little magnet on the timing gear that the cam sensor gets its reading from has came apart. You have to remove the timing gear to replace it.
 

mony0_8

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#8
None, Have just replaced hundreds of the cam signal sensor interrupters on '88 and up 3800s because they fall out of the housing and sometimes stick on the timing gear at the wrong spot causing erattic running issues! Have not had any problems with '96 up though.