1988 Boniville code 41

[bigbird0001]

I have a 88 boniville sse with a code 41 that will not reset it is a 3.8 motor does anyone have any sugestions left the Batt. cable off for 30 min and still there Thank you Bigbird

[Jrs3800]

Could be one of a couple of issues..

More than most of the time an Interrupter( Cam Magnet ) has jumped out of place and this leaves the ECM with no cam signal.. Its also possible to have a bad cam sensor( rare ) or a bad wire/s to the cam sensor.. so there are a few possibilities...

[bigbird0001]

ok will check those out and thank you for the reply

[MagicRat]

FWIW a code 41 is not such a bad thing. Replacing the sensor is pretty easy, but as noted above, it's usually the magnet that has come off or is defective. This is a lot of work to fix.

When the ECM loses the camshaft position sensor, the fuel injection system goes into a default mode. It can no longer operate (fire) the fuel injectors sequentially, so it reverts to a "batch fire" mode, where 2 or more injectors fire at the same time.

In my experience, the batch fire method does not seem to affect drivability. With my '88 Bonneville, I got slightly more engine power in the 'batch fire' mode, with no apparent loss of fuel economy. But the engine did run just a bit rougher, with an occasional mild stumble at throttle tip-in.

[Jrs3800]

Its not reverting to batch fire, it still fires the injectors individually... The cam signal is used by the ECM as a #1 TDC reference so that the ECM can run in true SFI.. Without the #1 TDC pulse the ECM will have no idea where true #1 TDC is and will have the injector timing a bit off... Most of the time the car will start and run ok,l if it runs bad simply restart, chances are pretty good that it will run better..

I guess I should say the injector timing is what will be messed up..

When I went in to replace my interrupter I went ahead and replaced the timing chain as well being that I was there..

[MagicRat]

Originally Posted by Jrs3800

Its not reverting to batch fire, it still fires the injectors individually... The cam signal is used by the ECM as a #1 TDC reference so that the ECM can run in true SFI.. Without the #1 TDC pulse the ECM will have no idea where true #1 TDC is and will have the injector timing a bit off... Most of the time the car will start and run ok,l if it runs bad simply restart, chances are pretty good that it will run better..

I don't have my GM service manual in front of me, but as I recall, it explained the situation like this:
The crank trigger determines the actual injector timing (which in this case, is still working). So the injector timing is correct, but the ECM cannot determine which injector to fire first for proper sequential injection, so it used a batch fire mode.

Although I said "batch fire" I seem to recall the injectors will fire two as a time, not all at once.

[Jrs3800]

Book says...

If the cam signal is not present at start up a code 41 will set and the ECM will start sequential fuel delivery in any old random pattern, with a 1 in 6 chance of the fuel delivery being correct..



The 3800 Vin C will stay in SFI mode, but will not be exact in the injector timing... You could start it one time and it will be really close and the car will run good... You could start it another time and have the car run very sluggish...

The 3300 V6 is another story...

[slingslingbinks]

Here's a bad cam sensor still in the cam gear if u want to see it.

I see it's a old post, but i'm doing one as we speak.

[Biomistake]

I just fixed a code 41 in my 89 bonneville. it had thrown the cam magnet. There it's a step by step process on how to do it without taking the timing cover off. Basically you remove the water pump pully, the cam sensor, rotate the crank until the magnet hole lines up with the cam sensor hole, then j-b weld a replacement magnet in. the how to is here:

http://padgett.performanceresearch.us/cars/cammag.htm

Hope that helps.
But if you need to replace the timing chain you might a well do it the right way.
L8r.