EVAP Ldp Reed Switch Doesn’t Open

2000, 328Ci, 147kmi

My Service Engine Soon light is on and when I pull the codes, I get 8D, EVAP Ldp Reed Switch Doesn’t Open. I'm using a Auto Enginuity scanner with enhanced BMW software, so that is the BMW factory code. When I clear the code, the problem typically reoccurs in ~ 5 driving cycles and the number of times the fault occured (fault frequency) is always 1 regardless of the time/driving cycles that I wait to pull the codes.

Can anyone provide diagnostic help?

1. I'm assuming the LDP pressurizes the system and the reed switch reacts to the pressurization. Does the switch open or close when the system is pressurized?

2. Does this code point definitely/strongly to a specific component?

3. Is there a way to test the pump (LDP) and the reed switch?

4. Are there other system components that could be causing this problem that I should check?

I've had this problem for about a month. I recently replaced the MDK (throttle assembly), but the timing of the problem is not exactly coincident with the throttle replacement, so I doubt that they are related.

I have the same issue with my 323ci. Did you every find out how to fix it? Thanks.

I'm not sure yet. I replaced the LDP which in my car is purchased as part of the charcoal cannister assembly. But I haven't driven it enough cycles to say with confidence that it's fixed yet.

Prior to replacing the LDP, I manually pressurized my system, and there were no obvious large leaks, but my method was not precise enough to determine if there could have been a small leak.

My car has the MS42.0 engine control system. In this system, the reed switch will open and close as the pump operates, and then stay open when the system is pressurized if there are no leaks. If the code 8D means the switch never opens, then this suggests the pump is not operating, the reed switch (part of the pump assembly) is bad, or the electrical connection to the switch is faulty. The pump not operating could be caused by a bad pump, faulty vacuum feed to the pump (the pump is powered by vacuum), or a faulty electrical connection to the pump which activates the pump.

I said "If the code 8D means the switch never opens" because in my exerpience you can't always take these descriptions literally. It could mean that the switch doesn't open under a certain test condition or it could mean that it never opens.

Anyway, I decided to replace the pump/switch. I did this prior to gaining a more thorough understanding of how the system operates which would have allowed me to check out the vacuum and electrical connections. If the new LDP doesn't fix the problem, then I'll spend some time checking the vacuum supply and electrical signals to the LDP.

Did you ever figure this out? I just replaced my charcoal canister assembly as well, but I am still getting this code 8d also.

Does this code ever trigger a CEL for you? Mine doesn't seem to, but I'd appreciate having it go away nonetheless!

Yes, I did get it fixed. I had lost the vacuum supply that powers the LDP. For MS42.0, there are two vacuum connections to the LDP/cannister assy. One goes from the cannister to the purge valve to purge vapors from the cannister. The other goes from the pump to the back of the intake manifold. On my car, the vacuum line had come off of the intake manifold. On later models, BMW went to an electrically power LDP. But if your LDP is powered by vacuum, I'd start by checking that you have a good vacuum supply at the pump. If you don't then trace the line back to the intake manifold and see if you have any problems with the line.

Here's a good reference for MS42.0. See pages 46-50 for the LDP.
http://www.beisansystems.com/misc/SE...ROL_SYSTEM.pdf

The fault never generated a CEL, only the Service Engine Soon light.

I know this is an old thread but this really helped me fixed the same problem I have on my 99 328i. The connection from the back of the intake manifold to the LDP got disconnected causing the engine light to come on. After reading this thread got my flashlight and found the problem. Thanks also for the link about the emission system.

i got this same code, can u give me the general area to find this vacume that u found loose, i got a 99 bmw 328i and im having the same issue, i believe my disconnection might be the same at the intake manifold, just wondering if u can point me in the right direction as to where did u look under the hood, thanks Ray

2ndary air pump is the most common, and ccv valve, done all those, charcoal canister pump replace and still same issue, moving on to replace fuel breather valve... will update if this solves the problemmmmmmmmmmmm......

Look at this link to a drawing of the intake manifold in the area of item 19.
http://www.realoem.com/bmw/showparts...95&hg=11&fg=40

It's impossible to see it in the car in that it's located between the manifold and the firewall. Remove the cabin filter and housing which sits at the top of the firewall. This is easy. You can then slide your hand down into the location between the manifold and the firewall and feel for the loose vacuum line. If you find it, you just slide it back on the nipple on the manifold.

I doubt that this would come off on it's own. The vacuum line runs through a bracket on the dipstick tube. I had removed the tube to access my throttle body and had jarred the line loose in the process. This line acts as the vacuum source for the LDP. With it disconnected, the LDP won't work and you'll get an evap emissions failure.

Hope this helps.

Thanks for your response, I really appreciate members like u that offer knowledge without flaming others, i actually found that it was still connected, but the bottom hose on my ccvv was loose it look like the mouth connection had widen enough to let air through the sides, i tell you must of this vaccuum issues are just bad hoses or connections, well i replace that hose with a new one, reset the CEL, and so far so good, 2 days driving no light , Yesssssssssssssssssssssssssss after a year of troubleshooting IM claining victory...!!!!!!