00 S70 Electrical Issues, an untraceable short?

deardeergod · Post by **deardeergod** » 17 Mar 2017, 08:27

I posted here last year with an issue my car was having. The vehicle would go into limp mode, the ETS, ABS, and BRAKE lights would come on along with the speedometer, tacometer, and odometer going to zero. I assume some other sensors were offline like the O2 sensor because it would idle poorly.

A restart would bring the dashboard back on, but the transmission would still be in limp mode. The car would have to be off for about 20 minutes for the ECU/TCM to reset (or something).

The throttle body was the first thing to be replaced and that made no change. My mechanic and I figured it was a peak or a dip in the voltage that would throw these faults. After months of this issue happening a few times a week the battery was replaced on a whim. And the issues stopped. A month later the alternator died. We figured that was the root cause of the issue and the new had battery staved off the voltage issues enough.

After nine months of everything being good the problem is back, the exact same as it was doing before. What now? Battery cable? Some other wiring bit? Is there a short in the system and I'll never be able to track it down? Any insight would be helpful.

Post by **abscate** » 17 Mar 2017, 08:46

Perhaps you can link back to the other thread, but was the ignition switch, electrical part ever evaluated??

that is common to all that stuff

Post by **bmdubya1198** » 17 Mar 2017, 08:48

Being that everything cuts off, it sounds like it might be battery related. When your transmission goes into limp mode, do you have an up arrow light?
Back when my transmission was doing that, it turned out to be a smashed connector near the air box and fan. I'll post a picture later, couldn't hurt to check.
Ignition switch is also very possible, makes a lot of sense to me especially that the problem had gone away and come back after some time.

deardeergod · Post by **deardeergod** » 17 Mar 2017, 09:10

The ignition switch was replaced last year when we trying to track down and fix the issue. The up arrow has only come on once, that was when I was running errands and the car was being turned on and off frequently without having time to reset. When the arrow did come on, it didn't act any differently.

My first post about it is here: viewtopic.php?f=1&t=73766&p=390143#p390143
My post about it being "solved" is here: viewtopic.php?f=1&t=75361&p=400873#p400873

I have conspiracy theory about it now. It often faults after it has been sitting in the sun for awhile. Maybe there is some thermal expansion that's causing a pin to go out of place? However, it doesn't always happen when the sun is shining and can happen on a cold cloudy day too.

Post by **bmdubya1198** » 17 Mar 2017, 15:54

Those OBD codes definitely seem wiring related. I had P1618 when my connector was broken. I'll post a picture soon of the connector I'm referring to. I believe it somehow links the TCM to the transmission, but I'm not completely sure. Basically, it was interrupting communication between the ECU and TCU, therefore my transmission was stuck in its fail safe program. It sounds awfully similar to the issues you're having, except this seems to be on a larger scale.
You may want to check all visible connectors under the hood, and maybe pull off the wiring harness cover(s) near the ECU box and make sure all wires are in tact. It could be that a wire's coating has stripped down over time and is shorting out.

Post by **scot850** » 17 Mar 2017, 17:16

My project 2000 V70 base had a TCU and ECU fault lights on before I bout it. Long story, but the result was there was TCU and ECU had corrosion on the connectors. The dealer removed the TCU and ECU and cleaned the contacts with a Wurth product and a cotton bud, dried it, and then fitted/removed them a couple of times and reset the units and so far so good.

Neil

Post by **bmdubya1198** » 17 Mar 2017, 17:40

Pictures... the connector with the electrical tape on it is the one I repaired. These larger connectors tend to be quite important... make sure all of yours (that you can see) are in tact.
This is between the intake hose in front of the air box and the battery if it's hard to see.

Post by **sleddriver** » 17 Mar 2017, 18:29

deardeergod wrote:After nine months of everything being good the problem is back, the exact same as it was doing before. What now? Battery cable? .

check the +cable connecting the battery to the main fuse box. Also verify your battery gnd cable. Obviously you tickled something when the battery was replaced, which is a hint.

Post by **abscate** » 18 Mar 2017, 05:36

Have a good look in your fuse box , and remove the top layer to look at the relay board for melting and other stuff.

Feel the battery cables on the idling car to see if you can detect resistive heating too.