[dcsonnenberg]

SOLVED, Stupidly crossed power cables.

Hey guys, I’m in trouble and need some help.

I just finished replacing the head gasket on an e90 2006 325i. After putting the car back together I reconnected the battery and 3 things happened immediately.

1. Brake lights came on (including 3rd at top)
2. DMTL Pump started and runs continuously without key
3. Water Pump started and runs continuously without key

With key inserted, I cannot get the the 2nd “RUN / ON” position.
I press the start button once and I get to Accessories 1st position.
I press the start button a second time and it shuts the car off.

This happens whether I step on the brake pedal or not.


Car ran and drove fine before the repair, it was just leaking a bunch of oil from the head gasket partly due to the broken aluminum head bolts.

I’ve done a few engine swaps on E90 and E92, and I like to separate the looms at the ECU connections. Everything came apart as expected and went back together smoothly.

I have redone all of the connections at and around the ECU. No change.
I have tried unplugging the IBS wire and unplugging the water pump. No Change.

Now, when I insert the key, it jumps into accessory and radio comes ON without pushing start button. 1st push of start button now shows the car off.

The key fob barely hangs in the holder, it easily falls out. I have a spare ignition / key reader and will try swapping that out to see if that makes a difference.

Not sure what to do or where to go from here….

[mecheng77]

What electrical parts were removed when you were replacing the head gasket ?

[Tunafish]

Try disconnecting the IBS from the battery.. The IBS is sensitive to electrical spikes.. This might let you start car if its the issue and you can go from there.. Its the blue plug coming off of the negative post which looks like picture..

[smass]

Check for bent pins on the ECU connections.

[dcsonnenberg]

Originally Posted by Tunafish

Try disconnecting the IBS from the battery.. The IBS is sensitive to electrical spikes.. This might let you start car if its the issue and you can go from there.. Its the blue plug coming off of the negative post which looks like picture..

I'll try that. I disconnected the large blue cable from the positive terminal block, guess that's not the same thing?

[dcsonnenberg]

Originally Posted by smass

Check for bent pins on the ECU connections.

That was one of the first things I checked. Thankfully everything looked perfect.

[dcsonnenberg]

Originally Posted by mecheng77

What electrical parts were removed when you were replacing the head gasket ?

What was disconnected?

Valvetronic Motor
All Injectors
All Coilpacks
Both Cam pos sensors
Both Vanos Solenoids
MAF
Altenator
Compressor
O2 sensors
Every connection in the ECU compartment was separated and the ECU plugs were take apart (as designed)
All the intake evap sensors
Postive cables on firewall posts

[Tunafish]

The large blue is IBS+ but what i read its the connector i had picture. Never had to verify this so not sure of it will make a difference but whats a one minute try...

[dcsonnenberg]

Originally Posted by Tunafish

The large blue is IBS+ but what i read its the connector i had picture. Never had to verify this so not sure of it will make a difference but whats a one minute try...

Oh I'm definitely going to try! Thanks for the suggestion

[dcsonnenberg]

Unable to read codes. Power must not be getting to the ECU.

[dcsonnenberg]

Hey everyone, just following up to let you know that I solved the problem.

Since there was no power getting to the ECU I decided to check the 5-pack of fuses in the ECU / DME compartment.
All 5 fuses were good, so I checked for 12 Volts for each of their power leads.

I found 12 volts at each of the power leads.
AND
I found 12 volts on each of the opposite leads.

I knew then that I had power on ground somewhere, YIKES!

So after literally praying for God to intervene, I started looking for my mistake knowing better what to look for.
I found it:
There is a ground wire that comes out of the ECU compartment that is attached to the grounding post on the strut tower.
I had accidentally put it on the POSTIVE POST!!!

I rectified the mistake and everything runs perfectly, no codes.
Praise God I didn't fry anything with such a stupid mistake.

Cheers!