2000 V70 XC Throttle Problem or ECM module

htschek · Post by **htschek** » 05 Apr 2015, 10:48

Hi all,
I am looking for a bit of advice after a lot of digging around on this site.

I have the car listed above. It barely starts, runs rough, can't make enough power to move at all even in gear, and the dash board is a Christams tree. But, it doesn't give me any codes! My first assumption was the main computer was toast but then I started reading here and various other places and realized that maybe the throttle control could be an issue or the MAF or some combination.

So I am just looking for a little advice on how to determine if it is the ECM or the throttle so I don't start replacing to discover something isn't the issue.

Note: I have done plenty of mech work on this car but no electronics other than the ABS control unit.
Thanks,
Henry

Post by **kahl** » 05 Apr 2015, 10:55

What is your mileage? What color tag, white or yellow, is on your throttle body. I am leaning to a worn throttle body, MAF would throw codes. Any sign of any vacuum leaks?

htschek · Post by **htschek** » 05 Apr 2015, 13:52

HI All and Kahl,
Well I got a big old clue for you all. After screwing around a bunch with it earlier this week, the battery was getting pretty weak from repeated starts but just enough to not turn the engine. Lights and everything were still coming on. So we took the other car down to jump it and when we did it fired up and ran just like normal as long as the cables were connected to the other car. You could even gun the engine and it didn't die. But the minute you removed the cables, the car sputtered and died and the dash lit up. While it was powered off of the other battery via the cables I could even read codes and the catalyst temp code was the only one and that one is always there.

I measured the voltage on the battery terminals:
Engine off (key off too): 11.2 V
Engine off, key on: 7.5 V
Engine on attached to other car (really measuring other car's voltage out): >12 V
Engine on, no attachment to other car, sputtering and about to die: 7.5V

It hadn't occurred to me that the charging system or battery could be a problem because clearly the control module wasn't controlling. Now I think that 7.5V must be below the voltage that operates the module. So now my questions is: could this be anything but the alternator? Would a bad battery alone do this by somehow knocking down the voltage coming out of a good alternator?
Thanks again,
Henry

Post by **Ozark Lee** » 05 Apr 2015, 14:21

Do you have or know anyone who has a battery charger? I would start by fully charging the battery and then see if most of the warning lights continue to come on while the car is running. A bad alternator does light up the instrument cluster like a Christmas tree. At 7.5 volts the computer will try to make some decisions but they are always wrong decisions.

...Lee

htschek · Post by **htschek** » 05 Apr 2015, 14:26

Thanks Lee. That is what I feared. I have everything I need to fix it in my garage, including the battery charger. But the car isn't in my garage...might just have to hit up the neighbor to yank it up the hill for me so I can get a charger on it....

Post by **precopster** » 05 Apr 2015, 15:27

The regulator in the altetnator has failed.
With 7.5V with engine running that's a sure thing. Charging the battery will get you home. The Bosch FOOM 145229 or equivalent regulator suits your car.

I don't think it can be reached in a P80 turbo engine bay without removing the alternator. Once you remove it this will help:

htschek · Post by **htschek** » 05 Apr 2015, 17:48

Thanks Mike. Confirmation is always nice before tearing in. Is there are thread here on getting the alternator out? I have a reasonable mechanical skill and tooling but haven't done this job on this car.
H

Post by **Ozark Lee** » 05 Apr 2015, 19:17

On a 2000 the alternator is easy.

Remove the battery cables.

Remove the serpentine belt (or at least release the tensioner and get it off of a pulley and yank it out of the way).

Remove the power steering pump and just set it aside. You don't need to disconnect the hoses to and from the power steering pump, just get it out of the way.

Remove the wires from the alternator.

Remove the alternator bolts and pull it out from the top. The bolts all go in from the front side of the car. Pay attention to the bolt lengths, I think there may be a couple of different length bolts but I can't remember for sure.

Reassembly is the reverse.

The way the 1999 and 2000 alternator bolts on it is much easier than on the '98 and earlier cars.

...Lee

Post by **precopster** » 07 Apr 2015, 07:37

As above ^^ I always drain 2-3 litres of coolant & remove top radiator hose but this may be optional.