1991 325i SRS light doesn't come on

[Vincenze]

They are 6 and 7 in the 1989 wiring diagram.

Now, you just need to check if the pin #6 gets 12V in ASSY.
And check that the wire from the pin #7 is connected to the pin #1 on the SRS module. Disconnect the connector from the SRS module and connect the pin #1 to the ground.

[salvadorwill]

Just found that if I ground pin #7 and put power on pin #6 the SRS lights up. No idea what's going on here.

[salvadorwill]

Yup, ok, figured out the pin number thing. Looks like my check panel connecter doesn't have a pin #3. Confirmed that pin #4 on the connector does have power in Accy.

[Vincenze]

The picture shows the pin numbers. But it's a good idea to match the wire colors.

You may use thin wires to get to the contacts.

[salvadorwill]

You mean test the tiny little pins on the back of the check panel? What can I use to connect to those tiny pins? Also, how do I know which pin is which number? There are 14 pins, and I don't see a map for them in any manual.

I tried just putting 12v on the SRS light and it did come on, so at least I know that the bulb and socket are ok. I also swapped in a "known good" check panel, and its SRS light didn't come on.
btw, thanks for your help, I appreciate it.

[Vincenze]

Odd that pin #3 Red isn't connected to anything on the SRS side, no? Why would a always hot 12v wire go to a dead end? Pin #4 violet does have power when turned to Acc. I tried connecting pin #4 violet to pin #4 Gn/Vi on the SRS side, and then testing to see if any of the other connections could get the LED to light up, and nothing happened. I also tested grounding each pin on the SRS side while the #4 to #4 connection was on Acc, and still nothing.

Ok, you have Power.

You're supposed to connect the pin #1 Brown/Black to the ground.
That Brown/Black wire is connected to the pin #3 in the Check panel connector. Disconnect it, and check the wire resistance between the pins. It should be 0.

The Violet Power wire is connected to the pin #4 in the Check panel connector. It should have 12V in the ASSY position.

Connect 12V to the pin #4 and ground to the pin #3. The bulb should light up. If it doesn't, the bulb must be changed, or there is another problem with a contact in the Check panel.

[salvadorwill]

Odd that pin #3 Red isn't connected to anything on the SRS side, no? Why would a always hot 12v wire go to a dead end? Pin #4 violet does have power when turned to Acc. I tried connecting pin #4 violet to pin #4 Gn/Vi on the SRS side, and then testing to see if any of the other connections could get the LED to light up, and nothing happened. I also tested grounding each pin on the SRS side while the #4 to #4 connection was on Acc, and still nothing.

[Vincenze]

I do have power, just not on the pin#4 violet, instead it is on pin#3 which is a red wire.

You say the the pin #3 is not connected to the SRS module.
It's not in the diagram. It can be obsolete.

According to the diagram, the power must come from the violet wire.
Another violet wire coming from the same connector C200 should be connected to the pin #4 of the connector in the check panel.

[salvadorwill]

I do have power, just not on the pin#4 violet, instead it is on pin#3 which is a red wire.

[Vincenze]

If there is no Power, it doesn't mean that the SRS module is dead.

You should follow the Violet wire to the connector C200, pin #4.
It should have power when the ignition key is in the position ASSY.

Check the view of the connector C200 on the page 142: https://www.armchair.mb.ca/~dave/BMW/e30/e30_89.pdf
It says that the 10-pin connector should be on the steering column. It should be connected to the ignition lock.

You'll probably have to take out the steering wheel to disconnect the plastic covers around the steering column.

[salvadorwill]

Did some tests, here is what I found:
The connector coming from the unit has the same colors/locations as what you show (#1 Blue/Bk, #2 Wt/Vi, #3 empty, #4 Gr/Vi, #5 Bk/Yl, #6W/Yl). On the side that plugs into that connector it goes: #1 Br/Blue, #2 Empty, #3 Red, #4 Violet, #5 Bk/Gr, #6 Wt/Bk. I tested pin #4 violet, and no power, however pin #3 red does have 12v. I also tested connecting pin #1 Br/Bk to ground, no light. Tried it with and without power. Only idea at this point is that the unit is dead, but also wondering why my wires differ from the wiring diagram. Why does my violet not have power, and this random red one does?

[Vincenze]

Thanks, I will give it a shot. When you say "the SRS block" I assume that is the orange box behind the headlight switch, right? And by "LED should light up" you mean in the check panel? Just making sure I'm clear.

Yes, the SRS computer. There are some on eBay, they are not very expensive.
If I remember correctly now, it's not an LED, but a light bulb, it can be changed from behind the check panel.

I just followed the wiring diagram from the link above.
If there is an error in the SRS system, that bulb must flash, and you can count the flashes to find the error. But if it doesn't flash, then the SRS computer can be dead.

[salvadorwill]

https://www.armchair.mb.ca/~dave/BMW/e30/e30_91.pdf

Disconnect the 6-pin connector C240 from the SRS block. It's probably better to disconnect the battery before doing that, and connect it back after you disconnect the connector.
Connect the pin #1 (Brown/Black) to the Ground and turn on the ignition key to the ACCY position. The LED should light up.
Check the pin #4 (Violet/Yellow). It should have 12V.

Thanks, I will give it a shot. When you say "the SRS block" I assume that is the orange box behind the headlight switch, right? And by "LED should light up" you mean in the check panel? Just making sure I'm clear.

[salvadorwill]

I have to make everything on this car work, I'm obsessive. This is one of the only features I haven't restored, so I am gonna try and figure it out.

[Vincenze]

https://www.armchair.mb.ca/~dave/BMW/e30/e30_91.pdf

Disconnect the 6-pin connector C240 from the SRS block. It's probably better to disconnect the battery before doing that, and connect it back after you disconnect the connector.
Connect the pin #1 (Brown/Black) to the Ground and turn on the ignition key to the ACCY position. The LED should light up.
Check the pin #4 (Violet/Yellow). It should have 12V.