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The craziest problem with 96 Volvo 850 T5

Help, Advice and DIY Tutorials on Volvo's extremely popular car line -- Volvo's 1990s "bread and butter" cars -- powered by the ubiquitous and durable Volvo inline 5-cylinder engine.

1992 - 1997 850, 850 R, 850 T5-R, 850 T5, 850 GLT
1997 - 2000 S70, S70 AWD
1997 - 2000 V70, V70 AWD
1997 - 2000 V70-XC
1997 - 2004 C70

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misha
Posts: 3920
Joined: Sun Dec 07, 2008 4:09 pm
Year and Model: '97 850 2.5 20v
Location: Serbia
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misha

Re: The craziest problem with 96 Volvo 850 T5

Post by misha » Sat Aug 10, 2019 2:29 pm

Did they checked TCU for fault codes?
Erikv11 have good point about this.
TCM,unlike ECU and ABS control unit will not clear the fault codes itself when parts are being replaced.
They will remain stored untill read and cleared even if parts is replaced...AND will not proceed further untill codes are read and cleared.
My point is that they should check TCM and see what it have to say about it.
TCM also needs at least VOL-FCR or special Volvo scan tool to communicate with it.
Generic/universal ones will not work with TCM.
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redbeak1


'97 850 2.5 20v /fully equipped/ Motronic 4.4 / polar white wagon
'91 Citroen XM 2.0 SI /fully equipped/mandarine red metallic
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

redbeak1
Posts: 6
Joined: Sat Mar 21, 2015 8:38 pm
Year and Model: 850t5 1996
Location: new jersey
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redbeak1

Re: The craziest problem with 96 Volvo 850 T5

Post by redbeak1 » Sat Aug 10, 2019 8:11 pm

misha wrote:
Sat Aug 10, 2019 2:29 pm
Did they checked TCU for fault codes?
Erikv11 have good point about this.
TCM,unlike ECU and ABS control unit will not clear the fault codes itself when parts are being replaced.
They will remain stored untill read and cleared even if parts is replaced...AND will not proceed further untill codes are read and cleared.
My point is that they should check TCM and see what it have to say about it.
TCM also needs at least VOL-FCR or special Volvo scan tool to communicate with it.
Generic/universal ones will not work with TCM.
I drove 400 miles since my last P0120 code including what my dealer mechanic put on. Would the TCM let me go this far without throwing the code again? I will print out all the responses and take it to another dealer when I get into trouble again. I will be pulling a motorcycle trailer this week another 350 miles. I never know when it will leave me stranded. But all these great responses give me hope.



redbeak1
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Year and Model: 850t5 1996
Location: new jersey
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redbeak1

Re: The craziest problem with 96 Volvo 850 T5

Post by redbeak1 » Sat Aug 10, 2019 8:27 pm

abscate wrote:
Sat Aug 10, 2019 3:32 am
See sticky thread above on wiring diagrams.

Resistance measurement is an art of itself and Is hard to do correctly. Have you removed and sprayed the contact staff with cleaner ?
I agree that doing a resistance test can give very elusive results. I just repaired my 17 year old Kenmore dryer that didn't ignite. I measured ohm resistance on the old gas coils and compared them with brand new ones. They were all in range and very close in results. By replacing the coils it solved the ignition issue. If I had followed the OHM results only, I would still be troubleshooting.

Since my Volvo problem is so sporadic, wouldn't I just be better off replacing the 3 wires from the TPS to ECU since no problem was found with the wiring during the resistance test?



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Clemens
Posts: 961
Joined: Thu Sep 03, 2015 12:34 pm
Year and Model: 96 855 R + 94 855 T5
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Clemens

Re: The craziest problem with 96 Volvo 850 T5

Post by Clemens » Sun Aug 11, 2019 3:20 am

yeah, give that a shot. you could probably just run a temporary fix before hacking up the wiring loom permanently. if you have a chance, get a spare tps connector off the junkyard.


Summer: 1996 855 R
Winter: 1994 855 T5M
Donor: 1995 854 10V

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