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2000 V70 2.5D MAF Problems

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Old Mar 29th, 2015, 19:18   #1
Richard_TD
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Default 2000 V70 2.5D MAF Problems

Our recently acquired V70 TDi isn't boosting properly, and wasn't when we got it. It's a late model with the MSA 15.8 system. I thought the waste gate being held on with jubilee clips and wire might have been the root cause but there was no change when I fitted another turbo.

A VIDA-DICE scan showed two codes, before and after the new turbo was fitted- ECM-000B Mass air flow (MAF) sensor - Signal too low and ECM-001D Turbocharger (TC) control valve - Signal too low. I believe a previous owner fitted a new MAF sensor, so I'm ruling that out for the moment.

I've checked the voltages at the MAF plug and got

1. +5.02V
2. close to 0V
3. 0V
4. +5.01V
5. 0V

Some Googling suggests that Pin 2 should have +12V. Is that correct, and if it is where should I be looking? The wire just disappears into a harness but I don't know where it goes. Is there a fuse anywhere? Would it be ok to connect it to another 12V supply?

For the moment I'm not looking at the TC Control valve, I've a feeling it will start getting the right signals once the MAF is working.
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Old Mar 29th, 2015, 19:33   #2
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You can view MAF response on vida and it should rise and fall with revs.
There are also multimeter back probing tests you can do to look for voltage changes whilst revving.
If the previous owner fitted a cheap non genuine MAF, it could well be the problem despite it being new.
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Old Mar 29th, 2015, 20:48   #3
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The MAF value stays constant on VIDA, which I believe is the default value when there isn't a signal. Even unplugging the sensor doesn't make it change.

Since I posted the above I've managed to find the bit on VIDA that tells me Pin 2 should indeed have battery voltage so the next move has to be to get that working I think. I'm tempted to temporarily connect it directly to the battery to see what happens.
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Old Mar 29th, 2015, 21:58   #4
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Update- the MAF worked when I hotwired it and its code stayed cleared. I'd still like to find out where the other end of the supply wire is though, so I can fix it properly.
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Old Apr 6th, 2015, 19:09   #5
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Genuine Bosch maf for your 15.8 model are less than £50, but sounds like the harness has a break in it, hence not getting power to it. If you can't find the break I don't see the harm in splicing power from elsewhere in? There might be a reason its not possible but I can't think of any just at the minute, just remember there is 12v and 5v
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Old Apr 7th, 2015, 13:59   #6
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I've taken 12V from another source for now and it's working ok. I've worked out what route it takes now so I'll be running a new cable soon.

The TC valve also had a broken wire and I've run one over the top of the engine temporarily, which has cured it. Again I'll be running a new wire through the trunking.
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Old Feb 7th, 2020, 09:21   #7
rosssi
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Quote:
Originally Posted by Richard_TD View Post
Our recently acquired V70 TDi isn't boosting properly, and wasn't when we got it. It's a late model with the MSA 15.8 system. I thought the waste gate being held on with jubilee clips and wire might have been the root cause but there was no change when I fitted another turbo.

A VIDA-DICE scan showed two codes, before and after the new turbo was fitted- ECM-000B Mass air flow (MAF) sensor - Signal too low and ECM-001D Turbocharger (TC) control valve - Signal too low. I believe a previous owner fitted a new MAF sensor, so I'm ruling that out for the moment.

I've checked the voltages at the MAF plug and got

1. +5.02V
2. close to 0V
3. 0V
4. +5.01V
5. 0V

Some Googling suggests that Pin 2 should have +12V. Is that correct, and if it is where should I be looking? The wire just disappears into a harness but I don't know where it goes. Is there a fuse anywhere? Would it be ok to connect it to another 12V supply?

For the moment I'm not looking at the TC Control valve, I've a feeling it will start getting the right signals once the MAF is working.

Hi,


You resolve this problem connect 12 V to pin 2? I have the same problem, my Volvo 2,5 TDI model year 2000 have problem with MAF and if I check voltage at connector have the same as you
1. +5.02V
2. close to 0V
3. 0V
4. +5.01V
5. 0V


You connect 12 V to pin 2 and after this, all working? Thank you for your reply.

R.

Last edited by rosssi; Feb 7th, 2020 at 09:43.
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