Air pump '98 S70

crlande · Post by **crlande** » 02 May 2019, 12:23

Hello,
Any theories on why the air pump would run for several seconds at a stop light or a similar situation on fully warmed up vehicle?
P0410 occasionally after it would run but no codes last couple days.
Thanks.

Post by **RickHaleParker** » 02 May 2019, 13:53

Flaky pump relay. Contacts shorting when coil not energized.
Pump +12V shorting to another +12V.
Relay coil +12V shorting to another +12V.

crlande · Post by **crlande** » 02 May 2019, 14:08

That makes sense. Good place to start poking around, Thanks!

Post by **erikv11** » 02 May 2019, 16:42

That's completely normal, the air pump is supposed to come on occasionally at stop lights. This has been reported many times before for P80 cars and unless it is coming on all the time, there is nothing to check out (but checking is free and usually doesn't hurt things!).

About the P0410: you already know the pump works so I'd start by checking for vacuum leaks, or just by replacing all vacuum lines related to the SAS.

crlande · Post by **crlande** » 02 May 2019, 18:17

Also sounds reasonable. I was fairly sure I have never heard either of the car's pumps come on after the initial start up phase. The occasional code must have made me keen on listening for it. Thanks.

Post by **RickHaleParker** » 02 May 2019, 20:00

The function of the SAS system is to burn off excess fuel from the rich starting Air/Fuel mixture and get the catalytic converter up to operating temperature. After that there is no reason for the pump to run. The pump running when it should not be running will trip P0410.

If it was not for the pump running when it should not be running, I would tell you look for leaks in the SAS system or defective valve.

If you monitor the input to the pump relay coil. Your be able to tell if the ECM is commanding the pump to turn on or if the power is coming from somewhere else.

Post by **erikv11** » 02 May 2019, 23:20

We can all agree with you RIck that it is not intuitive, but still it's normal behavior. People have posted about this many times over the years. These days many P80 owners just eliminate the air pump when P0410 pops up, so you need to look to the old posts,

e.g. from Moderator MadeInJapan and one other MVSer, pump running at stop lights without p0410: viewtopic.php?t=20348

Post by **RickHaleParker** » 02 May 2019, 23:27

Common and/or not unheard of does not make something normal, anymore then repeating something over and over make it so.

Post by **abscate** » 03 May 2019, 03:22

I would guess there is a Low voltages drop somewhere that is fooling the ECm into thinking it’s a new start cycle. The obvious correlation To a stop sign is the transition from alternator to battery’s voltage.

Can we agree it’s a common occurrence, without the judgemental “ normal” or “abnormal”?

From the thread above

Well, problem solved for now. After the tech used a Multi Tester Pro scanner with Volvo software to turn on the air pump manually in the test mode, it's been working ever since. I installed an LED across the pump relay coil to see when the relay picks up and it comes on always after a cold start and occasionally at a stop light. I also discovered something interesting - it apparently does not come on unless the car is (or has been) in motion. If I wait for it to come on in the garage before moving, it doesn't. That agrees with what the owners manual says about the pump, that it comes on when the engine is cold and the car is in motion.

Thanks for the suggestions.

Wow. This one is complicated. ECM is taking inputs of temp, speed, mixture, closed loop?

Post by **RickHaleParker** » 03 May 2019, 04:08

abscate wrote: 03 May 2019, 03:22 Can we agree it’s a common occurrence, without the judgemental “ normal” or “abnormal”?

Clearly not unheard of but not enough data to declare it common.

You might be on to something, I have seen startup routines triggered by a brown out.