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ECU Ground Connections Under Manifold Location?

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

warmblood58
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Re: ECU Ground Connections Under Manifold Location?

Post by warmblood58 » Mon Feb 29, 2016 11:11 am

Thank you, (I have full dash and instrumentation except the whole lower bank of warning lights (2 rows) located along the bottom of the instrument panel (both right and left) These are the lights that come on in position 2 right before starting ( I think about 17 or so, like SRS, ABS, oil, battery, etc. Thanks! This car sat for six months with a dead battery (previous owner did this) but did run up until that time. At first, I did not have dash lights but I bridged the dimmer pins and voila, had dash again but still no warning/indicator lights. Perhaps a reset or other though I have been reading about volatile memory, very important to keep these ECU's energized. Thanks again for your help! Also, this car has IPD's flashed ECU upgrade -

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erikv11
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Re: ECU Ground Connections Under Manifold Location?

Post by erikv11 » Mon Feb 29, 2016 12:37 pm

You might want to grab another ECU while you are messing around with possible wiring issues. For sure any turbo ECU from 95-96 will do just fine, although the emissions may not match and you could get a CEL for that. If you could only get the CEL to show ...
'95 854 T5-R, Motronic 4.4, 185k
'96 855 NA, 145k
'98 S70 NA, 220k (living out west)
'98 V70, T5 tune-injectors-turbo, LPT engine, 286k
'06 S60 R, 167k
'99 Camry V6 :shock: 125k
gone: '96 NA 850 210k, '98 NA V70 182k

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abscate
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Re: ECU Ground Connections Under Manifold Location?

Post by abscate » Mon Feb 29, 2016 12:43 pm

warmblood58 wrote:Thank you, (I have full dash and instrumentation except the whole lower bank of warning lights (2 rows) located along the bottom of the instrument panel (both right and left) These are the lights that come on in position 2 right before starting ( I think about 17 or so, like SRS, ABS, oil, battery, etc. Thanks! This car sat for six months with a dead battery (previous owner did this) but did run up until that time. At first, I did not have dash lights but I bridged the dimmer pins and voila, had dash again but still no warning/indicator lights. Perhaps a reset or other though I have been reading about volatile memory, very important to keep these ECU's energized. Thanks again for your help! Also, this car has IPD's flashed ECU upgrade -
I keep trying to ignore that upgrade since its just another variable in the mix (I know nothing about them, so I can't add value here)

The program in the ECU isnt volatile and doesn't require voltage to retain itself.

Have you found the dash wiring diagram on the web yet??
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1999-V70-T5M56 2005-V70-M56 1999-S70 VW T4 BMW
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warmblood58
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Re: ECU Ground Connections Under Manifold Location?

Post by warmblood58 » Mon Feb 29, 2016 7:56 pm

My next move is to check wiring diagram to see why warning light circuit might differ from other instrumentation. If ECU was fried, I would think cranking would be shut out with other functions =might try to reset tomorrow

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erikv11
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erikv11

Re: ECU Ground Connections Under Manifold Location?

Post by erikv11 » Mon Feb 29, 2016 11:35 pm

I don't think anyone is suggesting your ECU is bad, not sure what you are saying.

If you are referring back to my post, maybe I can clarify my point: you seem to really like that IPD flash, so as long as you are screwing around with wiring why not protect it and use a throwaway ECU for now? They are a dime a dozen at the wrecking yard.
'95 854 T5-R, Motronic 4.4, 185k
'96 855 NA, 145k
'98 S70 NA, 220k (living out west)
'98 V70, T5 tune-injectors-turbo, LPT engine, 286k
'06 S60 R, 167k
'99 Camry V6 :shock: 125k
gone: '96 NA 850 210k, '98 NA V70 182k

warmblood58
Posts: 141
Joined: Wed Feb 24, 2016 9:42 am
Year and Model: 1995 850 T5-r
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warmblood58

Re: ECU Ground Connections Under Manifold Location?

Post by warmblood58 » Tue Mar 01, 2016 11:02 am

I have a pair that came from an '97 but the markings are different - I don't see Motronic 4.3 labeling and thought about trying this but decided not. I did notice something strange the other day. While working around the battery and cleaning up connections, I hooked up negative terminal with blue wire only attached and no black neg cable (cable was hanging detached from neg terminal connection. In Position 2, the left bank of warning lights lit up but not right bank. When I noticed that I had not attached black cable back to post, I reattached and had no warning lights again . . . Does anyone one know if there is a third wire attached to ground at battery (in addition to black and blue cables at negative battery terminal? Previous owner admitted that he did not know much about electrical but I see evidence of where he has been . .

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abscate
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abscate

Re: ECU Ground Connections Under Manifold Location?

Post by abscate » Tue Mar 01, 2016 1:06 pm

You really don't want to do that. When you have 12 VDC on part of the car, and are grounding only parts of the the circuit, you will see all kinds of weird things happening - weird until you see that 12 VDC will ground itself through other components - none of which is good.

Sorting out wiring butchery is really nasty work.
Empty Nester
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1999-V70-T5M56 2005-V70-M56 1999-S70 VW T4 BMW
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JimBee
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Re: ECU Ground Connections Under Manifold Location?

Post by JimBee » Tue Mar 01, 2016 8:58 pm

Look for a ground behind the passenger side headlight, hard to locate. Somebody posted a thread on that a while ago, said it's a common source of no-start.
Good luck.

warmblood58
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Re: ECU Ground Connections Under Manifold Location?

Post by warmblood58 » Tue Mar 01, 2016 10:13 pm

Thank you!

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erikv11
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erikv11

Re: ECU Ground Connections Under Manifold Location?

Post by erikv11 » Sat Mar 05, 2016 10:52 pm

warmblood58 wrote:I have a pair that came from an '97 but the markings are different - I don't see Motronic 4.3 labeling and thought about trying this but decided not. ...
Just FYI, about this side thread: the 97 ECU (any P80 turbo ECU) will work just fine in your 95, regardless of whether the ECU is m4.3 or m4.4. If it's m4.4 you can enjoy the quicker startup and "other engine management advantages" (whatever those may be, exactly ... ). But an emissions code is likely as mentioned. If you use a 98 ECU the AC won't work.
'95 854 T5-R, Motronic 4.4, 185k
'96 855 NA, 145k
'98 S70 NA, 220k (living out west)
'98 V70, T5 tune-injectors-turbo, LPT engine, 286k
'06 S60 R, 167k
'99 Camry V6 :shock: 125k
gone: '96 NA 850 210k, '98 NA V70 182k

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