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(Solved) 98 V70 I Fenix - OBD ECM readout with LED not working Topic is solved

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MotorTheresa
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(Solved) 98 V70 I Fenix - OBD ECM readout with LED not working

Post by MotorTheresa »

Good evening,

Since blue V70 is on the road again I wanted to get a deeper look into the ECM and its DTCs. Getting a bad start occasionally which throws a DTC.
Used this LED rig described here http://volvo-turbo.de/obd-ii.html but LED stays dark. Always.
Am I doing something wrong?
IMG-20240707-WA0067.jpg
IMG-20240707-WA0067.jpg (23.03 KiB) Viewed 577 times
IMG-20240707-WA0068.jpg
Last edited by MotorTheresa on 28 Apr 2025, 03:11, edited 1 time in total.
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misha
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Post by misha »

Fuse ok?
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MotorTheresa
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Post by MotorTheresa »

misha wrote: ↑07 Aug 2024, 12:01Fuse ok?
checked all fuses. I say: yes
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Post by misha »

Possible reversed led polarity?
Did you tried it directly to a car battery?
'97 850 2.5 20v / fully equipped / Motronic 4.4 from the factory / upgraded with S,V,C,XC70 instrument cluster / polar white wagon
History of Volvos in the family:
'71 144 S
'73 144 De Luxe
'78 244 DL
'78 244 DL
'79 244 GLE
'85 340 GLS
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hausmeister
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Post by hausmeister »

Never used that gadget... Are you sure it is wired correctly? - I can't tell from the picture.
You can start by checking if there is the correct voltage for the led present after the resistor and 12v before.. and go from there I think. Test the LED separately etc. probably needs 1-3v. But you probably already got it working I hope.
Also why are you using pin 3?

In any case good luck with the Fenix.
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MotorTheresa
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Post by MotorTheresa »

Apologies, I just saw your replies here. Will follow the suggestions and check, then come back. Topic still open. Since I get MLC on rough startups it would be just perfect to see what's behind that hardware wise :)
Will follow up here, sorry for the late response.
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scot850
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Post by scot850 »

Have you got the ignition on to position II when testing?

Neil.
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MotorTheresa
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Post by MotorTheresa »

Yes, Pos II
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Post by MotorTheresa »

misha wrote: ↑17 Aug 2024, 13:20 Possible reversed led polarity?
Did you tried it directly to a car battery?
Today I have turned to this task again and indeed found the LED polarity wrong ... So, good hint!
Resoldered and will test tomorrow.
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P80GLT
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Post by P80GLT »

It is possible you will need to replace the LED with a new one as incorrect polarity can cause them to fail
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