code 41-cam sensor

[Guest imported_daddy3jr8]

90 reatta love it! get code 41,replaced sensor-not fixed- voltage at connector should be 8-10,i got 10.8 at both leads.I know now that car has had elec. prob. the fuse panel is in upside down( a dead give away).does anyone have any suggestions? has 117K.Thanks, Wayne Hamilton OH

[padgett]

Most common cause of a 41 is not a bad sensor, they rarely fail, but the magnet falling off the cam sprocket, did you check it ?

Is one of the few cases where the FSM procedure resembles software "help" from a certail large Bellvue company. Is entirely correct but not very helpful.

Some months ago we posted a 20 minute fix that did not require removal of the timing cover but did require slight modification of the "interrupter" and application of JB Weld.

As to having other electrical problems the answer requires three things

1) the factory service manual

2) a voltmeter (digital of otherwise)

3) carefull application of both

There is no simple answer.

[Guest]

Its fairly rare, but the channel in the PCM that reads the input from the sensor can also fail. An FSM is just about a nessesity on this or any other car this complex.

Bob Rich

[padgett]

PCM (powertrian control module) is a later designation. In the Reatta (except maybe the 91) it is still the ECM (engine control module). Am having enough trouble explaining the acronyms to most members with confusing things 8*).

Agree it is possible for the channel to fail but first would pull the sensor (one bolt) and visually (mirror & light help) verify whether the magnet has fallen off since it is quite common.

Mine has be working fine since replaced with the grind-insert-JB Weld fix through the sensor hole.

[Guest imported_daddy3jr8]

Thanks to all! JB had crossed my mind, now know that's the way to go.Sure do like the little thing.Had for 3 mo. and only drove it 4 or 5 times(it's like the sun-only comes out on nice days). Runs fine with 41, will fix improve power and performance? THANKS AGAIN-WAYNE

[padgett]

Most seem to run fine with loss of the cam sensor (at least mine did) but keep in mind that the cam sensor tells the engine when it is on the power cycle. Now keep in mind that on each coil discharge, two cylinders fire and they re selected so the two are 180 out.

What this means is that when the ECM thinks it is time to fire #1, both #1 and #4 fire. if the cam signal is lost when the ecm thinks it is time to fire either one, it does not matter which becoause one of the two will be right even if 180 out.

Injector pulsing is a fifferent matter since this is sequential with each cyl receiving a squirt during the intake cycle. Without the cam signal the engine is forced to revert to simultaneous injection instead of sequential which is not as efficient. Is may feel ok but the engine is not running as well as it could.

It is not hard to fix. I started with the $11 GM interrupter and just ground the flange off then inserted along with a liberal amount of JB Weld. Could be done in about 20 minutes

GM does not do this way at the factory because they can

1) insert the assembly from the back during assembly

2) inserted from the back, the magnet locks in place and needs no glue or drying time.

Dealers probably do not like because the engine cannot be started until the JB Weld dries (best to leave sensor off while drying so air can flow) so will tie up a bay.

[2seater]

The single most important reason the cam sensor is installed is for smooth operation at low speed and possibly a bit more efficiency. The injectors always operate sequentially on the 3800, but without the cam sensor to start the order properly it may be off by a little or a lot. Each time the engine is started, the starting point will change without the sensor. Many engines operate happily using a batch fire, (my old Taurus winter car for one), where half of them fire and then the other half. The total time for a single fuel injector shot to any one cylinder is only sixteen hundreths of a second at idle speed (two complete engine revolutions), which drops to forty eight thousandths of a second at 2500 rpm. If you factor in the fact that the intake valve is only open for part of the complete cycle, the only time the exact timing is of any consequence is at low rpms. At higher speeds the injectors are open before, during and after the intake valve is open. Disconnecting the cam sensor is actually a recommended test for some driveability problems. That said, it is more efficient with the sensor than without.

[padgett]

"The injectors always operate sequentially on the 3800" - nope, on the "C" engine they operate synchronously below 400 rpm and if the cam sensor signal is lost. See the description of EO41 (is on page 8D1-50 in the 88 FSM)

[2seater]

Hey Padgett, Happy New Year! Perhaps we are both right. The same 8D1-50 in the '90 FSM says this: "If the cam signal is not present at start-up, a code EO41 will set and the ECM will start sequential fuel delivery in any old random pattern with a 1 in 6 chance that fuel delivery is correct". I do not have an older manual but perhaps there was a change in the operation at some point. Perhaps there is also some other small change in the initial cranking where the '90 does open all injectors on the initial cranking,(priming shot), and then they stay off for two revolutions of the engine to use the initial fuel and pickup the cam signal to synchronize the injectors with the correct cylinder? Overall I don't believe it makes a whole lot of difference although cold operation would certainly be better with the cam sensor than without. The fuel just sits on the back of the valve until it opens, at least until there is good heat in the engine to vaporize it. The old Rochester fuel injection was a mechanical continuous flow system, was it not?

[padgett]

Yes, the Rochester was a continuous flow system and sprayed direcly on the intake valve. It also ran at about 150 psi from a mechanical gear booster pump (also had standard engine pump) driven by a cable from the distributer.

Had quite a few when I was into Corvettes & have some plenium castings I used to use for snow shovels and speaker stands.

[2seater]

Wow, I didn't realize they ran that high of pressure (10 bar), more than triple ours, although some of the newer ones are between 4 and 5 bar. I never had any direct experience except to ride in a couple. One hydro locked a cylinder from a leak and bent a rod on startup.