Code 41 Cam sensor on 1989 Buick Park ave, 3800 engine

JackC

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Hi friends:

My '89 Buick, 3800, Vin C, 182,000 miles has thrown a code 41 three times in the last week. CEL stays on for a minute or two and goes out.

Just prior to this code display I had an A/C relay stick closed and hold the compressor clutch on and run the battery down to .1 volt while the car sat overnight. Recharged battery installed new relay and all is well, except for this Cam sensor code. Perhaps this huge swing in voltage may have caused strange readings to the PCM or this is a red herring ??

BAT info for code 41 states, " Cam sensor signal was not received by PCM for the last 2 seconds while engine was running."

Is there anything I can check other than just replacing the sensor. Are they cleanable, repairable or ???

Should I ignore it for a week or month and see if it gets worse or better?

Thank, Jack
 

Gus

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OK, cam sensor signal is essential for correct injector firing.......if you lose the crank sensor, the car won't start....if you lose the cam sensor, the car will start, but only with one chance in six, that the injectors are firing at the right time....so it might start ok, but it might stumble a little or run rough.....

This code can be caused by several things.....one, naturally is the sensor......two, is the wiring harness to it....either a rub through condition, or the connectors in the harness where it joins to the sensor itself, or where it joins to the ICM.....could be an ICM......could be the harness to the ECM.....could b e the ECM...and finally, the worse case scenario, the magnet in the cam, could have fallen out....if it has, then there is nothing to "trigger" the cam sensor....

First thing to do, check the harness to the cam sensor......then remove the cam sensor.....with a flash light and mirror, slowly, manually rotate the crank bolt with a large wrench until you see the cam magnet line up with the hole.....if the magnet is missing/damaged, that is your problem.......this is a costly repair, as the front cover has to be removed to remove the timing chain and cam sprocket, to install a new magnet....

The two usual problems are the sensor or the missing magnet, then wiring problems....rarely the ICM or ECM, but have seen it happen....
 

JackC

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Thanks, Gus.

That was a VERY good explanation.

I will check wiring.

Am I correct that it is not the magnet since the CEL has not come on again?

Jack
 

Gus

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Yes there is a way to test it, but it has to stay in the vehicle......

You will need the "trouble tree" for code 41.....maybe one of the guys can post it for you.....

Basically, you will be monitoring the output signal of the cam sensor as you manually rotate the engine, watching the signal change from 5 volts to zero volts as the magnet passes by the sensor.....
 

billr

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I'm going to disagree with Gus a bit: if the cam sensor circuit goes bad there is a 50-50 chance of injector sequencing being OK, not 1-in-6. The cam sensor is just for determining if crank is on first 360 deg of a cycle or second 360 (ignoring V VT for now...). Is this a 3-wire sensor (Hall effect)? If so, the magnet is most likely part of the sensor assembly, not a "flying magnet" attached to the cam. With an intermittent it might be very difficult to catch the problem trying to test the sensor, it might be more practical to throw a new sensor at it. If that doesn't work, then go through the tedium of checking all connectors and wiring. If injector sequencing is off, engine operation isn't noticeably different with a "grocery getter" engine.
 

kev2

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I saw this checking trouble tree and intermittants ........... :idea:

Oh shit I just went over a 1998 trouble tree....
BUT the TSB is for your 89 .... I will regroup and add ouch
 

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Mobile Dan

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PURPOSE
The ECM uses the camshaft signal to calculate true Sequential Fuel Injection (SFI) mode or operation.

OPERATION
As the camshaft sprocket turns, a permanent magnet activates the Hall-Effect switch in the cam shaft sensor. When the Hall-effect switch is activated, it grounds the signal line to the ECM, pulling the camshaft signal line's applied voltage low. This is interpreted as a cam shaft signal. The camshaft signal is created as piston #1 is approximately 25° After Top Dead Center (ATDC) on the power stroke.

LOCATION
The camshaft sensor is located on the timing cover behind the water pump near the camshaft sprocket.

DIAGNOSTIC NOTES:
When the cam shaft signal is not received by the ECM, a Code 41 will set.
 

billr

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OK, then it is a Hall with flying-magnet. Yes Jack, not likely that magnet has come loose if the code doesn't reset immediately.
 

JackC

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Hi Billr:

Yes, it is a 3 wire sensor. It has not come on now for two days. The only thing I have done is to wiggle the connection right at the sensor to hopefully disturb it enough to "clean" the connection. So, for now, I am in the mode of "if it ain't broke, don't fix it"

Jack
 

91dynasty

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I would replace the sensor with a new one. I bet you can find a brand new one on ebay for $10-$15 If you ask me I would replace it anyways because it's 1989.
 

JackC

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Today,I made things worse. I was having NO problems, except that the CEL was coming on just for several times last weekend.

After having several code 41 show up last weekend, I decided to take a known good cam sensor (better than new, since I know it is OK) from my other exact perfectly running engine to determine if it was in fact the sensor.

Both engines are very clean, but I also used electrical cleaner and inspected and cleaned all connections, including the many wire connector to the coil pack, just for good luck.

Now the car will only start if I use 1 seconds worth of starter fluid. Spark is always present while cranking. After started it runs fine. But turn it off and it will not restart until I use another small shot of starter fluid.

That sounds like the fuel pump. I will get a gauge on it tomorrow. But this makes no sense to me that the fuel pump would act up just because I changed the cam sensor and cleaned the coil pack connector.

Any ideas??

Jack
 

kev2

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So the new tried and true CMP caused a no start..... What happened when you reinstalled the sensor with prior sensor?

I posted a TSB about intermittant #41 - did you check that possibality? could there be a wiring issue as you just moved harness/connector to install the lattest CMP?
 

JackC

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Kev: Yes. I reread your post and that is why I cleaned as many connections as I could, which were only the 3 prong cam sensor and the 12 wire connection to the coil pack. The other ends of those wires go to someplace I can not determine. They are buried under stuff.

I did change the fuel pump relay, just because I had a spare. No change of course.

I did try the old original sensor and it acts the same as the "new" sensor. No start unless a shot of starter fluid. CEL on all the time instead of only 5% of the time prior to my "fixing" it.

ONE time it did start after I rearranged the 12 wire connection at the coil pack. But never again. I am now suspicious of that area, but do not know how to check it out or how to fix it.

Now I am able to start it with the work around of turn key on, turn off, turn on, turn on and crank. That icicates to me that I have the old problem of a sticking check valve at the fuel pump in the tank, that I have been able to resolve with a bottle of Chevron Techron over the last 5 years. I will get some and try it.

Could be just a strange coincidence???

BUT, the CEL is on all the time now with the code 41. ???

Tune in tomorrow after the fuel pressure test and Techron.
 

billr

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You said (and confirmed with starting fluid) that you have spark OK. Have you checked for injector pulses during the no-start periods? Checked for 12V supply to injectors?
 
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