Hi guys

Fault code descriptions.(modis)
4525- glow plug cyl 5 activation
483d- throttle actuator
4677- throttle valve actuator

The car presented is a 530d it has no running problems as far as I can tell.

I may be nit picking but I think when the engine is switched off it comes to a holt a touch heavy.

I have not checked it out yet and know it could be more but I reckon cyl 5 glow plug is down.(I dont believe it is connected to the throttle valve code I am concerned with but, if it is I would not be suprised, I have seen stranger. assumption is the mother of all.... you know)

So the customer nipped in with EML illuminating. He as already been to dealer(nipped in again) seems this guy does not want to leave his new car anywhere. The dealers did a code read and cleared fault codes to see how he got on. He had a print out saying there was a problem with emissions but no codes? I wonder if that is so he can not google them?

I did a code read and pulled the above codes and told him he would have to book car in and LEAVE it with me so I could investigate the codes as clearing them was not going to fix the problem.

He agreed so I noted the codes and cleared them.

I got the car today and checked codes.
4525- glow plug cyl 5
483d- throttle actuator
(24 hours between code reads)

I cleared codes, started car, let run for a minute, turned off, same codes.

then

cleared the codes again.Ign on, glow plug code instantly.
started car and let run, glow plug code still. Turned engine off and both codes again. This is consistant.

As far as I know (I would like to know more) the throttle valve aids in DPF regeneration.

I dont know for sure but I was under the impression it helped EGR gasses flow by changing manifold pressure??

What I know for definate is that the valve cuts airflow to the engine to aid in efficient shut down.

My Modis is not completley up to date but it didn't tell me much and also couldn,t actuate the throttle valve.

The throttle valve is easy to access so I took the pipe off and sure enough the valve closed when the engine was shut off, and the code reappeared.

The throttle valve has 3 wires going to it
1- Battery volts through 10A fuse
2- Chassis ground
3- ECU control

So I scoped all 3 wires including Amp clamp on fused live.

blue-fused 12v, red-ground, green-ecu control, gold-motor current measured off 12v.

Full capture



Closer look at when the engine shuts down



A closer look at the ECU grounging the motorjust before current starts to flow.



The waveform is, ign on, start and run, turn engine off.

On start up battery volts drop to 7.7v not good but I wouldn't of thought it was my problem.

The current holds at about 3.8A after initial start up current fall.

When I shut the car off the ECU can be seen to control the motor,current starts to flow and the throttle flap does close(I saw this with my eyes)
yet a code is set?

Sorry guys I will get to my point soon

I do not have a different car to do the same test. If anybody has scoped this while shutting engine off, if you saved the waveform maybe you could see if my current and ground traces are correct.

The throttle body looks brand new(literally) it looks out of place with the older parts surrounding it. It is a pierburg unit, which I believe come on BMW as standard.

If the answer is in the current trace dropping to zero after the ecu starts to control the throttle flap or if it is something else I have overlooked (new to scopes) then could you point it out please and the rest of this post is probably nonsense

MY Theory (How is The Code Being Set)

After a cup of tea and think I came up with a theory.
There is no position sensor on the throttle flap.

The dealer said the unit is plug and play and does not need adapting or calibration.

Assuming the wave form is correct.( I think the ECU would only monitor the current if it went too high and blew the fuse and then there was no current flowing??)

So, I wondered,
Could the ECU monitor the crank sensor and see how long it took for the engine to completely stop?

If the throttle closes to shut the engine down it would probably cause a vacuum in the intake and could try and drag air in from intake leaks and the engine might run on longer and the ecu might blame the throttle flap.

So I smoked the intake and sure enough there is a leak coming from a blanking plug in the intake manifold. I am sure this is standard(not modified swirl flap remover caps) because I can see the typical BMW gasket tag sticking out the side of the cap. The swirl flaps generally have an unseen o-ring not a gasket.

The vehicle is coming back in next wednesday for the glow plugs diagnosing and the intake leak sorting out.


I know both jobs need sorting any way and there is only 1 way to find out but I can't wait till wednesday I wondered if you guys thought my theory was plausable or if I was way off the mark and finding the air leak was coincedental and I am over thinking it.

This maybe well known but I haven't come across any info.

I would appreciate any input
Cheers
James