P0505 Code 1998 540i e39 6-speed

[DopeG]

Okay, so I’ve been searching everywhere and could not find a fix to my situation and I could really use help. I’ve made an account for this exact problem.


I keep getting a p0505 code and ONLY when idle, the car will occasionally turn off altogether so I have to turn it on again and then it works fine till another random stop sign or light.

-I replaced a bad TPS sensor as recommended per my mechanic. Didn’t solve.
-I then replaced my IACV per mechanic. Didn’t solve.

-THEN my mechanic did a smoke test with 10lbs of psi and found a vacuum leak, we sealed it at the problem area with hose clamps so it currently has no leaks now.

Since the vacuum leak fix the car has not turned off on me on stop signs BUT the code ended up coming on again when I drove it home. My mechanic says he might have to clean the throttle body or get a new one altogether and on on about maybe if it’s electrical to replace the ECU if it’s seriously fried in the computer.

I would greatly appreciate what has helped you guys/gals to fix this issue and what clues or things that will help me. I need it to pass smog and I can’t do that with the CEL light on in CA. Thank you so much. I will be monitoring the post...

[Mach540]

P0505?
What is that?

[edjack]

Your engine has a conventional cable-operated throttle; it is not electronic. You may need a new mechanic.

IACV =?= idle air control valve. Test it by turning on the A/C. If the engine RPM increases about 100 RPM, the valve is okay.

BTW, Mach540 is correct to ask. We should ALWAYS define the code(s) we post. We can't expect members to waste time looking them up.

[DopeG]

So sorry, so the P0505 code is defined as being “Idle Air Control System Malfunction”

[edjack]

Make sure the hoses are properly attached to the IACV, and that it is working correctly. See my previous post for checking the valve.

[DopeG]

The valve is working as I got a new one as my mechanic said to. I’m thinking it may be the throttle body because the chassis of the car is 210k miles. May replace that

[DopeG]

Okay **UPDATE**

I will be cleaning the Throttle body tomorrow and replacing the second TPS sensor that sits on the side of the TB housing area as I heard this is the one that actually controls throttle position and that the one on top controls cruise control?? I replaced the top one with no fix so I’m assuming that info is right and I’m replacing because I got the p0505 “Idle air control Malfunction” and p0120 “Throttle/pedal position sensor/switch “A” Circuit”....

Please if you know anything about this issue give me some tips and fixes. My IACV is new so don’t tell me to clean it.

OBSERVATION: So I noticed while driving today, if the car is in gear right before a complete stop, then taken out, it will turn off.

Example, say I’m in 3rd coming to a stop sign, if I take it out of 3rd right before I stop, the car will turn off. No I don’t leave it in gear and stall it that’s why it’s explained. The RPM goes from idle speed to below like 200RPM and will either shoot back to idle or turn off at the stop.

Help me out you bimmer guys.

[DopeG]

At this point,

Replaced the IACV, both TPS sensors, air box filter with reusable non-oiled, cleaned the MAF sensor, and just cleaned my throttle body. None of which has solved my p0505, I’m going to run this car off a bridge, please someone what else can I check? ECM? I’m losing hope at this point and I have till feb. to smog.


206 views and 6 replies, is everyone clueless?

[geargrinder]

Yes we are "clueless". Sadly we are falling down on the job of sitting around all day waiting to answer your questions instantly and perfectly. 1000 apologies your excellency.

edjack gave you a test for the IACV. Did you try that? Or are you "clueless"?

If your car was just stalling then I'd have a handful of things you might be concerned with like MAF or O2's - and mainly MORE VACUUM LEAKS, but because the DME is throwing an ICV code... SOMETHING IS STILL WRONG with the ICV clearly.

What kind of new ICV did you get? Was it a proper new Bosch part that cost over $200? Or was it a knock off for $50 or so? Just because new doesn't mean good, especially with electronic items it seems. Did you double check it was / is installed correctly, as suggested? Its' kind of "clueless" to demand suggestions, get suggestions from reasonable experts, then just ignore those suggestions.

[JimLev]

Good response GG.
Hey Dope, for a new guy your starting off on the wrong foot, got it?

That code can reference any problem that has a direct result of the engine not idling where the DME wants it to whether it's a bad ICV, an air leak, sticky throttle body, etc.

[Mach540]

Ding, Fries Are Done!!!

[DopeG]

Well I ended up using my original bmw IACV and just cleaning all the gunk out. I understand if you can hear the valve move freely in your hands is a good sign. Throttle is not sticky anymore after cleaning the other day. Don’t take the “clueless” so personally

[edjack]

So, did that solve the problem?

[DopeG]

Unfortunately no, a weird issue indeed. My last option is replace the ECU and see if that works. Maybe the IAC relay is fried or faulty.

[JimLev]

I seriously doubt the DME/ECU is the problem.

[DopeG]

I seriously doubt the DME/ECU is the problem.

That’s my only option right now. Maybe I’ll get a new oem IACV but I’m running out of options.


I do have some logging that says :

“System B: Open loop - has not yet satisfied conditions to go closed loop (bank 1 or both)
Fuel System Status”

Not sure if that has anything to do with this odd issue.

[geargrinder]

That’s my only option right now.

That hardly seems the case.

These DME's hardly EVER puke the bed on their own. They are extremely tough and resiliant and durable.

Mechanics who throw that crap out for these ECU's are almost always craniorectally challenged.

The exception is if the MAP thermostat starts to leak at the electrical plug and coolant wicks into the DME connector and starts to corrode stuff.

Do you know you can't just toss an ECU in the car? That you need the DME virginized and then for it to be re-paired with the EWS (the "immob" as its called on other platforms) to start the car?

Though you (cluelessly) refused to answer the question, and are now suggesting a "new OEM" unit, we'll take that as confirmation that the new ICV was indeed a cheapo generic? If so there's a slim possibility that by bad coincidence, the old one is dead and the new one was crap... however my experience w those Bosch ICV's is that if you clean one at least you can get it to work for a while. Of course you never answered the question whether you indeed tried the test suggested which would be VERY helpful in trying to help you. Since you keep ignoring that let me try again:

TRY THE ICV TEST THAT ED SUGGESTED. Then tell us what happens.

Also... you are very inconsistent / confusing about what codes you have. Now you have "some logging" ?

Get a proper BMW compatible scan tool or PC (INPA or PASoft etc.) hooked up to the car and read proper (not PeePee) BMW codes and report those.

This is very likely an easy simple fix. Its almost certainly not a dead ECU. You just have to be sensible and patient and actually use the good suggestions you're being provided.

[DopeG]

That hardly seems the case.

These DME's hardly EVER puke the bed on their own. They are extremely tough and resiliant and durable.

Mechanics who throw that crap out for these ECU's are almost always craniorectally challenged.

The exception is if the MAP thermostat starts to leak at the electrical plug and coolant wicks into the DME connector and starts to corrode stuff.

Do you know you can't just toss an ECU in the car? That you need the DME virginized and then for it to be re-paired with the EWS (the "immob" as its called on other platforms) to start the car?

Though you (cluelessly) refused to answer the question, and are now suggesting a "new OEM" unit, we'll take that as confirmation that the new ICV was indeed a cheapo generic? If so there's a slim possibility that by bad coincidence, the old one is dead and the new one was crap... however my experience w those Bosch ICV's is that if you clean one at least you can get it to work for a while. Of course you never answered the question whether you indeed tried the test suggested which would be VERY helpful in trying to help you. Since you keep ignoring that let me try again:

TRY THE ICV TEST THAT ED SUGGESTED. Then tell us what happens.

Also... you are very inconsistent / confusing about what codes you have. Now you have "some logging" ?

Get a proper BMW compatible scan tool or PC (INPA or PASoft etc.) hooked up to the car and read proper (not PeePee) BMW codes and report those.

This is very likely an easy simple fix. Its almost certainly not a dead ECU. You just have to be sensible and patient and actually use the good suggestions you're being provided.

I will try the ICV test but yes my mechanic knows how to reprogram the new ECU to the car

[geargrinder]

Lol. Your mechanic so far has proved to be a total dumbass in other regards so i'm not sure I'd believe that but hey - best of luck!!

[DopeG]

Okay so I installed a new OEM IACV (~$200) from Germany from a reputable bmw parts website. Still getting the same code and issue of RPMs dropping below threshold causing car to die.

[JimLev]

If you turn on the AC does the idle increase?

[702KNITE]

tried switching your tps connectors around? this fixed a stalling issue on my 540 in the past.

[DopeG]

tried switching your tps connectors around? this fixed a stalling issue on my 540 in the past.

Hmm, I will definitely try that. Thanks for the tip!

[DopeG]

If you turn on the AC does the idle increase?

I do not think so and if it does it’s only for like 30 seconds then goes back to normal idle

[geargrinder]

If you turn on the AC does the idle increase?

LOL - he's been asked to do that for week now and finally you got him to come through!