[Glene]

I disconnected the battery to replace the valve cover gasket. After I had the valve gasket done and reconnected the battery, anxiously to start the car, not nothing happens. It does not crank and it seems like I can't even place the car in accessory mode. Radio and lock/unlock work, but engine gives me silence treatment.

Did I blow a fuse or something? When I reconnected the negative cable at the battery, I saw little sparks. But I think that is normal.

[Glene]

Originally Posted by Glene

I disconnected the battery to replace the valve cover gasket. After I had the valve gasket done and reconnected the battery, anxiously to start the car, not nothing happens. It does not crank and it seems like I can't even place the car in accessory mode. Radio and lock/unlock work, but engine gives me silence treatment.

Did I blow a fuse or something? When I reconnected the negative cable at the battery, I saw little sparks. But I think that is normal.

Update: Disconnected the IBS sensor and engine started.

[mainbearing]

Do you mean the IBS sensor is now DISCONNECTED? Or that it was disconnected and you just hooked it back up?

Changing the valve cover gasket should not result in the problem.

[ctuna]

I noticed the first time I took off the battery terminal to install a stereo
if I did not push the lug all the way down before tightening I did not
get a connection .
Also how's the battery voltage.

[E93Dude]

OK, so I know I probably don't do all my repairs 100% according to the BMW guidelines, but, ya know…stuff still gets fixed correctly and nobody gets hurt. My question is why disconnect the battery to do a VCG? I just went into the fuse box and pulled the fuel pump fuse.

[Glene]

Originally Posted by mainbearing

Do you mean the IBS sensor is now DISCONNECTED? Or that it was disconnected and you just hooked it back up?

Changing the valve cover gasket should not result in the problem.

I normally disconnect the negative cable when I work under the hood and disconnecting sensors. When I put everything together, engine does not crank, and it happens that the IBS sensor coincidently went bad this time. When IBS is dead, engine will not crank.

[relative4]

Originally Posted by E93Dude

why disconnect the battery to do a VCG?

Because bridging the under-hood positive terminal to the engine with a wrench is not a pleasant experience and will melt the fusible link on the battery.

[Glene]

Originally Posted by relative4

Because bridging the under-hood positive terminal to the engine with a wrench is not a pleasant experience and will melt the fusible link on the battery.

Disconnecting the negative battery when disconnecting bunch of sensors/modules is a good practice as protecting other modules being fried.

[gbalthrop]

Originally Posted by E93Dude

... why disconnect the battery to do a VCG? I just went into the fuse box and pulled the fuel pump fuse.
[Step #1 in depressurizing LPFP system on N54 I presume?]

Originally Posted by Glene

I normally disconnect the negative cable when I work under the hood and disconnecting sensors.
[Good practice when disconnecting ANY Connector if you do NOT know if a B+ (KL30) wire is in the connector.]
When I put everything together, engine does not crank, and it happens that the IBS sensor coincidently went bad this time.
When IBS is dead, engine will not crank.

Glene:
1) Did you have any IBS Fault Code, and if so, WHAT was the code?
2) How did you disconnect the Negative Battery Terminal? Any prying or impact on the IBS?
3) Which IBS Connector did you disconnect to get Starter to crank? (a) Red wire to rear of Power Distribution Panel, or
(b) Connector to chassis harness above & outboard of battery?

Attached are ISTA REP Document ScreenPrints showing Battery Negative Terminal (Clamp) removal as "Preliminary Task",
and procedure for disconnecting (-) Terminal.
George

[E93Dude]

All good points above on why to disconnect the battery. I have a plastic cap on the positive terminal/ electrical tape on the negative, and make sure the car is asleep before I work on it. After pulling the fuel pump fuses, didn't worry too much about residual pressure in the fuel system, I just put a rag under the stainless steel lines, and gently release the pressure when disconnecting them from the injectors.

In any case, Yes, disconnecting the battery is the safest ways to go.