Why does 20 pin connector blow fuse 26?

Tom Diab

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Jul 14, 2020
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Hello,
When I connect my Foxwell 510 scanner to an adapter for my engine 20 pin port, Fuse 26 blows.
Fuse 26
Engine control unit
Alternator
Cooling fan
Automatic transmission
10 Amp red

My scanner does not turn on either, although it turns on when connected to the OBDII.
Thank you for your ideas.

2001 BMW z3 Roadster 3.0
 

NZ00Z3

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Is there any particular reason for doing your scanning? Just looking for some more clues. Is there a trouble lamp up or something? Maybe the transmission light (Cog of Death)?

I have a Foxwell NT530 scanner that I use in my 2000 2.0L and 2000 3.0L Z3's without any problems on both ports. So its not likely the scanner.

When you plug into the OBD11 port, can you scan the engine computer (DME) OK? You need to have the cover screwed on the 20 pin diagnostic port under the bonnet/hood. If you can, then this proves that the DME is not the problem.

Your scanner will not turn on when plugged into the 20 pin port???
With a Multi-meter, check for voltages at these pins in the 20 pin port:
- Pin 14, 12 V, hot at all times
- Pin 16, 12 V, Hot in run and start
- Pin 19, ground, at all times

The DME and transmission computer (EGS) share pin 17 in the 20 pin diagnostic connector. They also share Fuse 26, so you might have a fault in your EGS. Try disconnecting the EGS and see if your scanner works with the 20 pin port.

The only other thing that it could be is your adapter plug that goes from OBD11 to 20 pin port. Check its pin out with the below picture.

 

Tom Diab

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Wow, thanks for your rapid reply! A little more background. I had the car at the BMW dealer and they were able to diagnose the acceleration sensors under the driver and passenger carpets needed replacement. They were causing the codes on my dash. Those codes were read via the 20 pin. The dealer said that the car had water in it and corroded those sensors under the carpets. I replaced those sensors and wanted to reset the faults. But those faults cannot be reset by the OBDII. So, each time I connect my 20 pin adapter to my Foxwell fuse 26 blows.
When I plug into the OBDII pin with the 20 pin cap on in the engine, my stupid foxwell says "No Communicating" after it goes through its detection steps. I have so many issues at once. Sadly, the dealer said there were no other issues with the car except for those under carpet sensors. Do you think they could have detected a bad EGS?
I will try testing the pins that you stated in the 20 pin.
Thank you very much
 

NZ00Z3

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I have not used the NT510, so don't know if its the same as the NT530 I use. I can either let the scanner do an auto-detect or I can manually select the vehicle to be scanned. I found that the auto-detect didn't work well and always manually select the vehicle. Have you tried manually selecting your car when connected to the OBD11 port?

If you can't communicate with your DME through the OBD11 port, then it could be:
- Your scanner
- The DME
- Something else connected to the diagnostic bus that is pulling it down/faulty.
 

cn55

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Hi

Had a similar issue when I as connecting INPA. Tnhe fuse would blow. Bought a new (more expensive) round 20 pin to OBD connector and no issues since.

May help if you can find someone with another 20 pin adapter.
 

mrscalex

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Some great info from @Murray Wall. But if the BMW dealer has recently connected okay then for the sake of £5-10 I would buy another round pin adapter first as @cn55 says. Some of these things are very cheaply made and may not be reliable.

The Foxwell has a very good reputation on here so my first thoughts don’t turn to that as an issue.
 

mrscalex

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Whereabouts are you Tom? Someone might even be local to you to help with swapping cables/testers around to isolate the issue.
 

Tom Diab

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Hello,
I was able to get reading from the engine 20 pin port. My previous problem was caused by a faulty 16 pin adapter! However, I have one fault. Can someone help me identify where and what this problem is? Can I fix it myself? thanks
 

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NZ00Z3

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Hi Tom

Pleased to hear that you have the scanner problem solved. It had me worried that you might have cooked something important.

The transverse acceleration or Yaw rate sensor lives on the floor under the carpet under the passengers seat (left hand side of the car). There are two sensors there, the Yaw rate sensor and the left side airbag impact sensor. Use the part numbers to tell them apart. The usual failure mode for the sensors is water ingress. So if you stick your hand under the carpet and its wet, you'll know that you have to dry out the huge sponge of foam rubber and find the water leak.

Once you replace the yaw rate sensor. It will need to be calibrated to the car. This is documented and the software is available free. You will need to buy some special leads which are cheap. You will be setting up INPA on a windows laptop and its associated tools. A link to the software and the calibration procedure is below. Read the first post well. You will be using Tool32 for the calibration.

The instructions are in section:
D. Using INPA and other BMW Tools with Z3
3. Advanced Sensor Calibration with Tool32
Z3 DSC Lateral Acceleration Sensor Calibration Instructions

https://www.bimmerforums.com/forum/...tions-Experiences-Discussions-Experimentation

The up shot of all of this, is that you will end up with two very good diagnostic scanner and will be able to sort many of your cars problems easily.

Regards

Murray
 

Tom Diab

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Hi Murray,
I am slowly progressing toward the accelerator sensor calibration. I have some questions if you can help.
First, I followed your instructions and the link to the other forum. I downloaded the BMW TIS software. But I see there is also a software named Tools32. I don't see where to download it. But now I am lost. I have the proper cables. Can you explain what the TIS and the Tools32 software do? Are they related? I also downloaded the pdf on how to calibrate the transverse sensors. Thank you in advance.
Tom
 

NZ00Z3

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Hi Tom

TIS is the technical resource/documentation for BMW's. It has wiring diagrams, service information, maintenance procedures. It does not have the wiring diagrams for the Z3's. For those you can go to the Resources section of this forum and the wiring diagrams are there. You need to know your build date and down load the right ones. TIS is also available online at https://www.newtis.info/tisv2/a/en/

Tools32 is a software program that you will need to calibrate the yaw rate sensor. It is bundled in the download pack called INPA. So download and install INPA and Tools32 will automatically be installed.

Hope this helps

Murray
 

Tom Diab

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Hi Tom

TIS is the technical resource/documentation for BMW's. It has wiring diagrams, service information, maintenance procedures. It does not have the wiring diagrams for the Z3's. For those you can go to the Resources section of this forum and the wiring diagrams are there. You need to know your build date and down load the right ones. TIS is also available online at https://www.newtis.info/tisv2/a/en/

Tools32 is a software program that you will need to calibrate the yaw rate sensor. It is bundled in the download pack called INPA. So download and install INPA and Tools32 will automatically be installed.

Hope this helps

Murray
Hi Murray,
I am finally getting around to calibrating my new yaw sensor I installed on my passenger side of my 2001 bmw z3 3.0
Are these the steps I take.
Connect my laptop to my 20 pin diagnostic port via the special usb adapter I bought
Start the INPA software
but then what do I do?
Thank you
Tom
 

Tom Diab

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Jul 14, 2020
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Hi Tom

You will be using the program called Tools32. It got installed when you installed INPA. There should be an icon for it on your desktop.

The instruction are here https://www.bimmerforums.com/forum/...sions-Experimentation&p=29437829#post29437829
Hi,
I followed the thread to to calibrate my lateral acceleration sensor and all was going so well with Tools32 and then I noticed that my jobs window was blank. I could not make the selections required in the thread you sent me. Any ideas? I have attached a picture. Much appreciated
 

NZ00Z3

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Hi Tom

I'm not a Tools32 expert, so can't help.

Suggest you join the Bimmerforums forum and post you problem at the end of the same thread where you got the instructions. The thread owner, Abe, is very good at helping people.
 
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