IPD sale XeMODeX - Experts in Volvo Electronics Free shipping all USA - Experts in Brakes
Did you know? 🤔
Logged in users can get email notification of topic replies Log in or register (free).
Amazon Link Buy your stuff using this and it helps MVS!

1998 V70 Engine compartment wiring harness removal?

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

kjhiggins
Posts: 38
Joined: Wed Sep 02, 2009 2:14 pm
Year and Model: 2010 XC70; 2006 S40
Location: Boston
Has thanked: 0
Been thanked: 0
United States of America
kjhiggins

1998 V70 Engine compartment wiring harness removal?

Post by kjhiggins » Mon Jul 21, 2014 1:47 am

I've been having an ongoing problem with my V70 (287k miles) frying ECUs. It's been four in the last 2 1/2 weeks, even after an independent Volvo shop took a stab and replaced the B+ cable to the fuse box. I'm at the point now where I'd like to gain access to/remove the engine compartment wiring harness and I'm wondering if there are any tutorials on the subject? I've done many searches with various terms for the harness but I've come up empty.

I should mention that I found a corroded ground behind the airbox on the strut tower and replaced that along with a bad engine coolant temperature sensor today. I also did some more checking for shorts but didn't find anything apparent when I checked the ECU socket terminals. So I put in another salvaged ECU, started the car and let it idle for 1 1/2 hours before taking it around my condo complex's loop drive for 1.1 miles. I then ventured a bit farther, going up the hill to a school about 1/2 mile away and returned home with no problem. I turned it off and back on, let it idle another hour and then took it for a more extended drive, including freeway at 70 mph. As I was nearing home and driving down a gentle incline the car died again. It made it 11 miles and 3 1/2 hours this time, as opposed to 6.2 miles and 15 minutes and 2.2 miles and 45 minutes (mostly idling) the last two times I thought it had been fixed.

So I don't know if it's something that's slowly killing the ECU or a loose wire that just happens to make contact and shorts at random times after I start driving. The car shows no signs of running poorly right before it dies and there are no OBD-II codes being stored.

Thanks!
2010 XC70 T6 180k; 2006 S40 T5 AWD M66 230k; 2004 XC70 280k; 1998 V70 288k (sold); 1970 Dodge Super Bee 383 Magnum 122k

Ozark Lee
MVS Moderator
Posts: 14798
Joined: Thu Sep 07, 2006 8:24 am
Year and Model: Many Volvos
Location: USA Midwest
Has thanked: 4 times
Been thanked: 49 times
United States of America
Ozark Lee

Re: 1998 V70 Engine compartment wiring harness removal?

Post by Ozark Lee » Mon Jul 21, 2014 6:28 pm

There is no connector for the engine wiring harness like there is on many domestic cars. It splits off to numerous places and goes through holes in the firewall on both the left and the right hand side of the car. Replacing the entire wiring harness is a daunting task and the better way to go about locating the problem area is to split the loom and inspect the harness for damage. It is still a PITA but it beats trying to replace and add new connectors to each wire.

...Lee
'94 850 N/A 5 speed
'96 Platinum Edition Turbo
Previous:
1999 V70XC - Nautic Blue - Totaled while parked.
1999 V70XC - RIP - Wrecked Parts Car.
1998 S70 T5
1996 850 N/A
1989 740 GLT
1986 740 GLT
1972 142 Grand Luxe

User avatar
erikv11
Posts: 9482
Joined: Sat Jul 25, 2009 2:03 pm
Year and Model: 850, S/V70, 06 S60R
Location: Iowa
Has thanked: 81 times
Been thanked: 244 times
United States of America
erikv11

Re: 1998 V70 Engine compartment wiring harness removal?

Post by erikv11 » Mon Jul 21, 2014 8:34 pm

kjhiggins, I sent you a PM.
'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, 285k
'06 S60 R, 165k
'99 Camry V6 :shock: 125k
gone: '96 NA 850 210k, '98 NA V70 182k

jimmy57
Posts: 6517
Joined: Fri Nov 12, 2010 9:25 am
Year and Model: 2004 V70R GT, et al
Location: Ponder Texas
Has thanked: 3 times
Been thanked: 218 times
jimmy57

Re: 1998 V70 Engine compartment wiring harness removal?

Post by jimmy57 » Mon Jul 21, 2014 9:16 pm

The ECM grounds are under the RH headlight under the black fiberglass/plastic core support. If you use a mirror and a 10 mm boxed end wrench you can tighten them.

Tell us more.
What happens?
DO you have any idea what circuit is affected?

kjhiggins
Posts: 38
Joined: Wed Sep 02, 2009 2:14 pm
Year and Model: 2010 XC70; 2006 S40
Location: Boston
Has thanked: 0
Been thanked: 0
United States of America
kjhiggins

Re: 1998 V70 Engine compartment wiring harness removal?

Post by kjhiggins » Tue Jul 22, 2014 11:48 am

Thanks - I was able to finally see it and disconnect it for cleaning. It looks a bit corroded where the wires are crimped in the terminal but not overly bad. I'm in the process of pulling most of the wiring harness up from where it goes just above the crossmember so I can clean and inspect it. The plastic tray is filled with grime from what I can see but I've got to disconnect a few more things before I can pull it up far enough to do anything with it. I've read about opening up the tray, cleaning the wires, and then separating them and spraying them with wire lacquer or some other insulating material in case any of the insulation has worn away due to the abrasive nature of the dirt and grime.

The issue manifests itself with my car simply dying while I'm driving it - no sputtering, no indication it's about to die. After it dies, there is no spark from the coil until I put in a different ECU (all the usual suspects were checked before changing the ECU) but I don't know what circuit is affected other than the coil signal circuit from the ECU (presumably, since there is a no-spark condition.) I've tried comparing resistance readings between ECU pins on one of my bad ECUs and a good one but nothing stood out as different. I've opened up two of them but there is no obvious physical damage like a burned or overheated area.
2010 XC70 T6 180k; 2006 S40 T5 AWD M66 230k; 2004 XC70 280k; 1998 V70 288k (sold); 1970 Dodge Super Bee 383 Magnum 122k

jimmy57
Posts: 6517
Joined: Fri Nov 12, 2010 9:25 am
Year and Model: 2004 V70R GT, et al
Location: Ponder Texas
Has thanked: 3 times
Been thanked: 218 times
jimmy57

Re: 1998 V70 Engine compartment wiring harness removal?

Post by jimmy57 » Tue Jul 22, 2014 12:30 pm

Has the coil been changed?

Does it have injector pulses when it has no spark?

The power stage is driven by a 3.5 +/- volt + pulse that lasts 20 milliseconds. The pulse when seen on a scope will have a ramp on its upper flank from charging a capacitor. The pulse will start at 3 v and rise to 3.5 v during the 20 milliseconds.

kjhiggins
Posts: 38
Joined: Wed Sep 02, 2009 2:14 pm
Year and Model: 2010 XC70; 2006 S40
Location: Boston
Has thanked: 0
Been thanked: 0
United States of America
kjhiggins

Re: 1998 V70 Engine compartment wiring harness removal?

Post by kjhiggins » Wed Jul 23, 2014 9:57 am

Yes, the coil was changed and this has happened with both the old and the new coil. I didn't check for injector pulses - I don't have a scope but presumably the shop I took it to, where they checked 'everything' does and did check but I have no confirmation of that. We're not exactly on speaking terms since their total lack of concern that the car died 6.2 miles after leaving their shop so I don't think I can check with them to see what all they did during their two hours of diagnostic work.
2010 XC70 T6 180k; 2006 S40 T5 AWD M66 230k; 2004 XC70 280k; 1998 V70 288k (sold); 1970 Dodge Super Bee 383 Magnum 122k

Jbw99v70t5
Posts: 3
Joined: Tue Feb 04, 2020 12:43 pm
Year and Model: V70t5 1999
Location: Portland OR
Has thanked: 0
Been thanked: 0
United States of America
Jbw99v70t5

Re: 1998 V70 Engine compartment wiring harness removal?

Post by Jbw99v70t5 » Tue Feb 04, 2020 12:44 pm

You might be having voltage spikes from your
alternator

Jbw99v70t5
Posts: 3
Joined: Tue Feb 04, 2020 12:43 pm
Year and Model: V70t5 1999
Location: Portland OR
Has thanked: 0
Been thanked: 0
United States of America
Jbw99v70t5

Re: 1998 V70 Engine compartment wiring harness removal?

Post by Jbw99v70t5 » Tue Feb 04, 2020 12:45 pm

Sorry voltage regulator

User avatar
abscate
MVS Moderator
Posts: 20028
Joined: Sun Feb 17, 2013 5:54 pm
Year and Model: 99T5 ,99S70,2005V70
Location: NYC, ALBANY NY
Has thanked: 273 times
Been thanked: 851 times
Trinidad & Tobago
abscate

Re: 1998 V70 Engine compartment wiring harness removal?

Post by abscate » Wed Feb 05, 2020 4:51 am

Old thread alert, from 2014

Interesting problem from OP though.

Don’t check resistances on an ECU with a voltmeter. You are putting current into it when you do this, and ungrounded , this might not be healthy.
Empty Nester
A Captain in a Sea of Estrogen
1999-V70-T5M56 2005-V70-M56 1999-S70 VW T4 BMW
Link to Maintenance record thread
Link To Volvo Glossary

Post Reply
  • Similar Topics
    Replies
    Views
    Last post