[nissubaru]

Been trying to figure this out for the past few weeks but I have had no luck. I even spent $500 on a new DME programmed to my car, the guy was honestly less than helpful besides taking my money. Plugged the new DME in this weekend and still no luck.


I'll try to simplify this post because a lot has gone on it seems. Codes I'm seeing are:

2E7C BSD data bus communications fault
2E84 BSD, message; electric coolant pump: Missing
2E8E BSD, message; intelligent battery sensor (IBS): Missing
2E98 BSD, message; alternator: Missing.

1. Spun bearing, replaced engine with used motor. Replaced rod bearings and a ton of gaskets in the process.
2. Previous owner modified the hell out of the car, has Fuel It! Throttle Body Injection and Ethanol Sensor wired in
3. Fuel It Throttle Body Injection is unplugged, red wire in the video. Ignore it
4. Either I screwed something up or the previous owners wiring was the problem but I had a wire short from one of the two MAP sensors due to a ground wire being spliced in.
5. My screw up was connecting the DME ground to the positive terminal by the fender (the piece that attaches to the charging post). The DME positive cable was incorrectly bolted to the ground lug on the fender.
6. Idk what caused the wires to short, it could have been the ghetto ground wiring or it could have been my screw up. I had melted wires on the JB4 harness so I removed the JB4 and the harness
7. Replaced 1 of the 2 engine wiring harnesses, the one that connects to the alternator, O2 sensors, AC compressor, MAP sensors etc. Ignition harness left alone.
8. Replaced DME with a cloned one
9. Tried two different batteries

Here's a video looking down into the engine bay, you can't really see much but you can hear how my car doesn't even crank. Is that the fuel pump that you can hear or is that the water pump?

I'm honestly kind of stuck at this point. I'm getting ready to throw in the towel and just have the BMW dealer diagnose it, but I'd hate to find out it's something like the starter. I replaced the engine so I can replace anything else. Just trying to avoid throwing more parts at the problem.

Things I think it could be at this point, honestly though the codes don't make much sense:

• Starter Relay
• Failed CAS, read somewhere that this would cause a crank, no start condition though whereas I have a no crank, no start condition?
• CAS Relay?
• Starter
• Alternator - new as of last year
• Water Pump - new as of 2 years ago

[feuer]

Don't feel bad that you replaced the engine and it doesn't start. I suggest you check first the positive battery cable in the truck if is exploded or not. If Ok then check, FRM. Lastly, maybe different DME, CAS and key combo first. If you don't have friend to let you test with their parts might be cheaper and faster to have BMW dealer just diagnose the issue.

[NinetyEight740]

Do you have voltage at the starter? A lot of times when something is Hooked up incorrectly or shorted under the hood you’ve blown a fuse at the power supply box on top of the battery.

[dpaul]

Originally Posted by nissubaru

2E7C BSD data bus communications fault
2E84 BSD, message; electric coolant pump: Missing
2E8E BSD, message; intelligent battery sensor (IBS): Missing
2E98 BSD, message; alternator: Missing.


Things I think it could be at this point, honestly though the codes don't make much sense:

• Starter Relay
• Failed CAS, read somewhere that this would cause a crank, no start condition though whereas I have a no crank, no start condition?
• CAS Relay?
• Starter
• Alternator - new as of last year
• Water Pump - new as of 2 years ago

The codes are clearly reflecting a problem with the bit-serial data (BSD) bus. This is a communication line connecting alternator, waterpump, oil level sensor, IBS (intelligent battery sensor) and DME. A break in a wire at any point on the bus will bring the whole thing down so you're going to have to figure it out eventually.

That said, it's not the reason you can't start the car.

If that clicking or clanking noise in your video is actually the starter solenoid, it means that your CAS is probably functioning correctly and mostly likely you have a) a bad solenoid/starter, b) a weak B+ supply to the solenoid/starter (perhaps due to corrosion at a connecting point) or c) a bad ground connection to the engine block. All assuming your battery is OK.

Of course, if the click is not the solenoid, everything I'll say from here on is useless.

Since you replaced the engine, I'll vote for ground strap - you had to disconnect it getting the old engine out and it is not uncommon for folks to forget about it. The straps corrode and fray with age anyway and may be the problem even if you remembered to reconnect it.

Fairly easy to test these things:

c) is easiest - connect a jumper-type cable from the engine block somewhere to the chassis somewhere.

b) is not that hard - get a voltmeter and put the positive lead on the charging point in the engine compartment (the thing with the red slide-on cap on it) and the negative lead on a chassis ground (not engine block). If you read anything less than 12, your problem is the cabling between the battery and the engine compartment. I'll disagree with Feuer here (although he's usually on the money) about the possibility that the BST (not BSD, not IBS) terminal at the battery is blown because if it was, I think you'd get no click.

a) get access to the solenoid/starter, which probably means removing the intake manifold. Use a jumper-type cable to put 12V on the solenoid nut opposite the one that the cable is attached to. If the starter turns, it's OK.

[nissubaru]

Originally Posted by dpaul

The codes are clearly reflecting a problem with the bit-serial data (BSD) bus. This is a communication line connecting alternator, waterpump, oil level sensor, IBS (intelligent battery sensor) and DME. A break in a wire at any point on the bus will bring the whole thing down so you're going to have to figure it out eventually.

That said, it's not the reason you can't start the car.

If that clicking or clanking noise in your video is actually the starter solenoid, it means that your CAS is probably functioning correctly and mostly likely you have a) a bad solenoid/starter, b) a weak B+ supply to the solenoid/starter (perhaps due to corrosion at a connecting point) or c) a bad ground connection to the engine block. All assuming your battery is OK.

Of course, if the click is not the solenoid, everything I'll say from here on is useless.

Since you replaced the engine, I'll vote for ground strap - you had to disconnect it getting the old engine out and it is not uncommon for folks to forget about it. The straps corrode and fray with age anyway and may be the problem even if you remembered to reconnect it.

Fairly easy to test these things:

c) is easiest - connect a jumper-type cable from the engine block somewhere to the chassis somewhere.

b) is not that hard - get a voltmeter and put the positive lead on the charging point in the engine compartment (the thing with the red slide-on cap on it) and the negative lead on a chassis ground (not engine block). If you read anything less than 12, your problem is the cabling between the battery and the engine compartment. I'll disagree with Feuer here (although he's usually on the money) about the possibility that the BST (not BSD, not IBS) terminal at the battery is blown because if it was, I think you'd get no click.

a) get access to the solenoid/starter, which probably means removing the intake manifold. Use a jumper-type cable to put 12V on the solenoid nut opposite the one that the cable is attached to. If the starter turns, it's OK.

I'm nearly 100% positive it's not my ground cable. I replaced it not long ago because it was frayed resulting in my battery not charging sufficiently and eventually not having enough charge to start the car. This was probably 2 years ago now, AND I replaced it again because the one I bought originally was too big. It was overkill for the amperage rating of our alternators so I went with a more flexible but adequately sized ground cable. I remember putting it back on but I'll definitely give it another check.

At this point I'm just going to order a new starter and a new starter relay. I will also do some diagnostics with a multimeter and one of those circuit/light testers on the starter before wasting time pulling it out. It's not that hard, I can probably have it out in 20 minutes (I have relocated inlets) but if I don't need it then no sense installing it. I just want to have the parts ready for this weekend when I go back to work on it (it's at my parents house). Relay is $20 and looks quick to replace so I'm gonna rule that one out first.


As for the possibilities of something back near the battery being fried, everything looks okay back there. I had to tinker with all the cables a bunch the past couple weekends because I was swapping batteries in and out. Back when I was chasing down the bad ground strap I bought a new battery so I'm pretty confident it's not that.

There are a bunch of related threads, one said the DME need to be replaced, one says there was a bad ground, another said the cable that runs from the battery in the trunk up to the front of the car was corroded/bad, another said it was a bad starter. I messaged one guy and he said his starter solenoid was bad.

You don't think it's my water pump or alternator right? I would say the alternator has nothing to do with the car running just yet, can't start it so that can't be it. Is that the fuel pump or the water pump that runs when the electronics turn on?

One last thing of note, my car speakers make a popping noise like every 5-10 seconds when plugged in. It's like the radio is bugging out. Idk what to make of this, I never tried to listen to any music to know if the speakers work or not but I have door chimes etc.

[Emilime75]

Originally Posted by nissubaru

...You don't think it's my water pump or alternator right? I would say the alternator has nothing to do with the car running just yet, can't start it so that can't be it. Is that the fuel pump or the water pump that runs when the electronics turn on?

One last thing of note, my car speakers make a popping noise like every 5-10 seconds when plugged in. It's like the radio is bugging out. Idk what to make of this, I never tried to listen to any music to know if the speakers work or not but I have door chimes etc.

Neither the alt or water pump should prevent the car from starting. The HPFP is mechanically driven, so it wouldn't make a noise like that. The LPFP is in the tank, so not likely that that is what you're hearing in the video, either. If the noise is the water pump, I don't know. Try to get your hand down on it and feel for vibrations while someone else tries to start the car. Obviously, watch where your hand is in case it decides to turn over.

The speaker's popping sort of points to a potential voltage/ground issue.

[oilcrankinject]

Did you figure out what was wrong? I had the same issue as you, rod knock. I too replaced my engine. Do you have voltage at your starter?

[nissubaru]

Originally Posted by svtfast

Did you figure out what was wrong? I had the same issue as you, rod knock. I too replaced my engine. Do you have voltage at your starter?

I had two issues, you can probably check both. Start with checking your grounds, all grounds really, but the first grounds you should check are the ones to the DME as well as the positive cables coming from the DME. See the pic below to see which ones I'm referring to, on the shock tower. I had these mixed up and that basically kept the DME unpowered and unable to connect to.



Once I realized this and corrected it I could get power to the DME and all that jazz but the car still wouldn't start for shit. I believe that is when this post came into play, the solution was actually quite simple, and again, related to a bad ground.

This time it was the negative battery cable/ground strap in the trunk that was corroded. Technically it was just the terminal itself that had gone a bit greenish white on the underside and around the ring that goes on the battery. I was only getting ~5V of the 12.6V that the battery was supplying to the rest of the car because of the weak connection. After cleaning up the ground cable terminal with a wire wheel the car started right up.

Hopefully it's that simple for you! But yes, do use a multimeter and check your voltages. You should get the same voltage up front that you get in the back. My problem was literally at the terminal though, less than 1/2 inch away from the battery and my voltage dropped to 5

[JuniorB]

The IBS sensor is a big red flag, was just reading up on that. If that’s old or corroded, it’s going to cause havoc and not start the car. The missing sign means no power to communicate with, make sure that IBS is going to the positive side, and check for power out. Something isn’t hooked up, or it’s hooked up to a ground. Double check everything at the battery, make sure it’s full, or new, and check all connections in the fuse box.

[nissubaru]

Originally Posted by JuniorB

The IBS sensor is a big red flag, was just reading up on that. If that’s old or corroded, it’s going to cause havoc and not start the car. The missing sign means no power to communicate with, make sure that IBS is going to the positive side, and check for power out. Something isn’t hooked up, or it’s hooked up to a ground. Double check everything at the battery, make sure it’s full, or new, and check all connections in the fuse box.

My IBS sensor was fine. No weird BMW bullshit here, as much as I seem to get confused by all of the electrical wizardry that this car has it was a cut and dry issue. I overlooked it because why the hell would the battery terminal be dirty/corroded if it's sitting in a nice clean trunk? But it simply was that, the car was only receiving 5V of power. IBS sensor or not, the car was never gonna start with that weak of a connection.