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Discussion Starter #1
Hi ,
my e34 m5 1992 3.6 doesnt do a flap test when starting.
New vacuum lines new solenoid .
flap opens when directly connected to 12 v.

What possibly go wrong
i have 2 modules and both not working.
How to test them what part may fail.
Opened them both the boards are good no bad connections and not burned.

Rpm is also working fine.

What else shoukd i check ?
thank you
 

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1. Ignition ON, do you get ~12V on the wire that goes from the solenoid of the resonace flap to the control unit?
2. Ground the wire that goes to the resonance flap and see if it operates
3. Power and earth OK
4. Does the TD wire get to the module? Can you hoop up a LED tester to see if it blinks while the engine is running?
 

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Discussion Starter #3
Hi thank you ,
We have snow here i will test today.

What is the TD wire?

I ll get back to you with results for the above tests

Regards
 

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Discussion Starter #5
Hi again,

Test result:
1-ingnition on 12v exist.
2- No ground available.
3- Wire of ground is good to control module.
4-Engine on if grounded the valve it opens never close unless i remove the vaccum line .
Also never close if i turn off the engine. Note it moves free by hand its not stuck.

Any idea ?

Thank you.
 

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I don't get exactly what you mean. Therefore I made a point to point test which I hope you can perform again...

Resonance control unit pin out:
  • 1. Blue/Black – resonance valve
  • 2. Brown/Black - throttle position full load input
  • 3. Black – engine speed input
  • 4. Brown/Orange - Ground
  • 5. Green/Violet - Power supply

Do the following, access the resonance control unit (placed together with the DME in the BOX under the hood on the right side).

  • 1. Use a voltmeter and turn it on voltage measurement (DC) and put black/ground wire from voltmeter on pin # 4 (ground) and red/positive wirre to pin # 5 (power supply). Turn on the ignition and engine. The resonance valve is power by the fuel pump relais and is only activated shortly during ignition on and permanently with a running engine.
  • Do you have ~12V?
  • 2. Remove the red wire from voltmeter and put it in pin #1 (resonance valve). Do you have 12V?
Leave the black / negative wire from the voltmeter connected to pin #4 (ground) during these measurements.

  • 3. Remove the red wire from voltmeter and put it in pin #2 (full load signal). Do you have 5V?
  • 4. If the engine is heated up or you want to Turn the throttle lever to full load, do you have 0V?
  • 5. Remove the red wire from voltmeter and put it in pin #3 (engine speed signal). Do you have ~12V?
  • If OK. Remove the wires from the voltmeter
  • 6.Get an extra wire and connect it to pin#1 (resonance valve). Short it to ground anywhere you like. The flap should be operated once you ground it.

I will try to make a manual for you as soon as possible with guide steps on how to identify problems. Please try the suggestions above and report back
 

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Discussion Starter #7 (Edited)
Thank you for the details please find below the test results in BOLD :



Do the following, access the resonance control unit (placed together with the DME in the BOX under the hood on the right side).

  • 1. Use a voltmeter and turn it on voltage measurement (DC) and put black/ground wire from voltmeter on pin # 4 (ground) and red/positive wirre to pin # 5 (power supply). Turn on the ignition and engine. The resonance valve is power by the fuel pump relais and is only activated shortly during ignition on and permanently with a running engine.
  • Do you have ~12V?
Confirmed 12V
  • 2. Remove the red wire from voltmeter and put it in pin #1 (resonance valve). Do you have 12V?
Leave the black / negative wire from the voltmeter connected to pin #4 (ground) during these measurements.

Confirmed 12V

  • 3. Remove the red wire from voltmeter and put it in pin #2 (full load signal). Do you have 5V?
YES
  • 4. If the engine is heated up or you want to Turn the throttle lever to full load, do you have 0V?
YES
  • 5. Remove the red wire from voltmeter and put it in pin #3 (engine speed signal). Do you have ~12V?
YES
  • If OK. Remove the wires from the voltmeter
  • 6.Get an extra wire and connect it to pin#1 (resonance valve). Short it to ground anywhere you like. The flap should be operated once you ground it.
IT worked

so we assume that the flap control module is faulty?
 

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so we assume that the flap control module is faulty?
99% chance it is. I have tot found a way to test the engine speed signal yet with easy measurement tools. But if your instrument cluster shows engine speed I have a good feeling it is correct. If you have a LED tester it should be possible to test the engine speed signal.
connect the terminal with a clamp towards battery positive and connect the probe to the engine speed signal pin. It should blink as it gets grounded by the DME/ECU. Once engine speed rises the frequency of blinks should rise equally.

We can conclude that the vacuum system and wiring are OK. Once you ground pin #1 the flap is actuated.

I don't know if getting a used one for you is easy? Otherwise I would try to repair the unit. Maybe there is a broken transistor. Otherwise remove current electronics and install an Arduino or other self programming device. Doubt the part would come cheap from BMW dealer.
 

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Discussion Starter #9
Thank you again for for your reply
I hv 2 with same issue.

I will try to fix one by interchanging parts.

If i ground #1 pin the flap opens

This means that all vaccum line are good .

I will keep you posted when i finish testing
Regards
 

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Discussion Starter #11
Thats strange if you have 2 with an equal problem. Try to measure the engine speed signal if possible!
Tested engine speed
With a light .

The light goes stronger with more rpm
Is this correct!


Below are the 2 modules

936361
936362
 

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Tested engine speed
With a light .

The light goes stronger with more rpm
Is this correct!

Yes.

There are 3 transistors/mosfets in the middle of the board.
Measure the resistance against all 3 connctions.

Transitor has 3 connections, base, collector and emittor
1. BASE - COLLECTOR
2. BASE - EMITTER
3. COLLECTOR - EMITTER

See how they behave. Make one is broken.
 
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