Yes, a vacuum issue, no vacuum makes a stiff pedal. No vacuum is caused by the engine not running, not vice versa.

 

Thanks for the quick reply, @Doug Huffman!

No vacuum is caused by the engine not running, not vice versa.

What I mean to ask is: If I were to remove the leak, would this make the brake pedal less stiff immediately (without a running car), allowing me to start the car, or would the car need to be running to reinstate the necessary vacuum first?

I am wondering if I need to depress the brake switch somehow to get the engine started and complete the repair.

 

Can you get your X5 into Accessories or Run mode? Like press the start without foot on brake?

Also do you have a scanner for BMW Enhanced codes?

 

Yes, the car “wakes up” just fine with a single press of the start/stop button. Regardless if the pedal is down, it fully lights up the dash and accessories on a second press.

I’m re-downloading Rheingold/ISTA-d now to get the codes.

 

You will have a stiff brake pedal without vacuum created by a running engine.

Even without vacuum, you should be able to easily depress the brake pedal enough to permit an engine start.

The stoplight switch on the brake pedal is an electronic device instead of a simple electro-mechanical switch. It may have failed, but other items are more likely.

The CAS relay is one of those items.

Also, check for broken ground straps under the hoo
d.

 

Try manually depressing the brake switch and see if it starts. Could be a linkage problem in the brake?

 

Although not the same, I had a similar problem recently. Everything worked (lights, accessories, etc…) but it wouldn’t even try to crank. After much hypothesis and fumbling around in the dark, it turned out to be the ground between the chassis and the block. I didn’t even get a voltage drop between the chassis and the block when I tested with a dmm. However, as soon as a load was put on that ground (trying to crank), it failed and everything shut down. Much like a battery can read good voltage, a load test is required to confirm a good battery. Those grounds are notorious in e70s so start with the basics.
Good luck.

 

Hi everyone. Thanks for your support. I went out of town for the holidays end of '22, and when I returned, the car cranked back up and resumed working just fine...until last week. Thus, the same issue has re-emerged 6 months later. I finally got ISTA-D running on my computer, but I'm unsure if it is connecting properly with the car. I'm posting here because of the off chance that it is in fact connecting to the car, but there is a fatal error when attempting to communicate with the ECU. Would appreciate any input. Thanks again for your help. In the meantime, I'll continue troubleshooting ISTA-D in case it's an issue with my K+DCAN. See screenshots below:

 

Could be an issue with your cable. Has it worked before? Maybe test it on a different car.
Otherwise I would check for power and a good ground on the engine computer.

 

Thanks for the tips, @xrviz . I ended up re-installing ISTA-D and it works now. Here are the codes. It looks like an issue with the CAS module. I'll look around for information on how to replace or fix it. In the meantime, if anyone has experience with this, please share. Thanks in advance everyone. Can't tell you how supportive it is to have a community like this.

005224 Transfer box (VTG): Oil wear
00A0B3 CAS: Engine start, starter operation

 

Follow up -- At first glance it looks like the issue could be with the CAS module or Starter. This post describes some troubleshooting steps. This will be my firs time troubleshooting electrical errors on the car. Funny - I was just thinking the other day that it would be nice to learn - you get what you ask for!

 

Is adding an additional ground strap safe to do? Looks like replacing the original could be far more work.