Multiple Scan Tool Communication Issue ?

Scott Technician Jacksonville, Florida Posted   Latest   Edited  
Network Communications
1996 BMW 750iL 5.4L (M73) 5-spd (5HP-30)

Looking for some direction or possible info. A … ) BMW e38 750il w/ no communication with DME's thru cardaq2 & ista-d. All other Nodes will communicate and using Matco launch same thing happens, DME's not found on network​.​ Now with Solus edge I get comm's , and data pids for both 20 pin and OBD2... under IHKA (a/c) controls, although very slow LOL. Now the symptom and issue with the vehicle seem to align with the code (in generic mode ) , P1270 MAF bank plausibility. Smells very rich at idle and bank to bank difference is about 5 grm/ps.. B1 2.34 grm/ps and B2 6.4 grm/ps.. I've swapped MAF's with no change, Just for S's&G's , Previous repairs were for very lean at idle due to the PCV blocks on back of intakes with rubber grommets bypassing air. Now at this point not looking really for an answer but reason why 2 tools show no comm's and 1 does. Should I trust the none OE tool? How do I clear adaptions or look at data?

Side note - I have tested voltage and Ohms at the 20 pin per ISTA test plan and Is good. Just doesn't make sense. Especially I have comms with the other Nodes on the CAN line. 

Is this a possible pre 96 pre obd2 issue or my tooling? I've reached out to Drew tech (still waiting on an answer) Did not contact ISTA support due to not having Icom hardware. 

Thanx for your time, any thoughts would be greatly appreciated,

Scott T. ASE Master L1

Jeff Owner/Technician
Baldwinsville, New York
Jeff Default

With 20 pin diagnostic port and OBD2 port, make sure OBD2 port has the cover on it, otherwise it will have comm issues and visa versa with 20 pin port, cover needs to be on it for OBD2 to work properly, I have seen bad resistors on the cover before causing a comm issue.

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Michael Mobile Technician
Clinton, Utah
Michael Default

Since the Drew Box was engineered for J2534 standards, anything more is a bonus. Surprised you can get anything on that old of BMW with it. The new Matco tool does not seem to be backward compatible past year model 2000. I could be wrong. I was helping a customer on a 1999 Infiniti and the tool would not communicate over the 14 Pin proprietary connection only Engine and Transmission on the

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Brian Owner
Parma, Ohio
Brian Default

I have little BMW experience, but is there a possibility that the snap on tool is internally grounding some pins? If it were a 16 pin dlc many aftermarket tools bridge the grounds making some problems go away.

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Rex Owner
Sarasota, Florida
Rex Default

Are you using the under hood BMW proprietary diagnostic connection (Big round screw-on cover)? If not, find someone with the necessary scan tool to do so. And as noted above, make sure the OBD2 cover is installed on the worthless OBD plug. The old Baum Iscan hand held scanner and Autologic work well on these old Beasts

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Steve Technical Support Specialist
Gainesville, Florida
Steve Default

On BMWs that have the 20 pin connector, they must be used for everything BUT the OBDII functions. The 20 pin will not work using OBDII protocol for the DME. If you have a BMW protocol tool always use the 20 pin if it exists. It was removed in around 2001.

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Scott Technician
Jacksonville, Florida
Scott Default

Thank you all for the responses. Hope I am replying in the correct format due to I'm on my phone. As most of you suggested , I did have the obd2 jumper cover on while using the 20 pin port .Like I stated earlier the Snap-on would connect with both ports , 20 pin and obd2 ( I have all pre obd connections for both Snap-on and Matco ). But j2534 nor Matco would see the dme's on the network . A

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Michael Owner/Technician
Cartersville, Georgia
Michael Default

Hi Scott, Ista really sucks on cars that have 20 pin connector. As Steve stated the only thing you can get out of the 16 pin is generic OBD2 information. Everything else is through the 20 pin. Have you pulled the oil dipstick to see if there is excessive vacuum while idling. That could cause your problem.

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