2000 S70 Base DTC P0505: 1275634 Air assisted control valve (AACV)

thankswww · Post by **thankswww** » 23 Nov 2013, 05:00

I've got a 2000 S70 base, Denso everything, non-turbo. This is a recurring DTC code that my car is throwing:

P0505 ECM-6207 Air assisted control valve (AACV) Flow too low

Here's the thing; the car idles perfectly and never fluctuates or dips. No idle problems whatsoever. What are the chances of the AACV being bad, without affecting the idle at all?

Furthermore, if the ECU thinks the flow is too low, will it make any adjustments to compensate for this that might affect the overall performance of the car? In other words, if my car idles perfectly, should I even bother with replacing this valve?

thankswww · Post by **thankswww** » 23 Nov 2013, 10:59

I wiped all of the codes, and then with the car shut off, I unplugged the AACV sensor. I then started the car. The code came back. I guess this means there is a wiring problem somewhere? If I unplug this sensor, and the PCM still throws the 0505 code, it has to be a problem with communication between the sensor and PCM, right?

Post by **jimmy57** » 23 Nov 2013, 13:02

Not necessarily. Feel the AACV with engine idling with it plugged in and then do the same with it unplugged. You should feel a faint but fast vibration in the valve if it is cycling. It might even operate with key on and engine not running for the testing.
I have seen that code with dirty throttle. The throttle is supposed to carry some of the airflow with AACV admitting the rest through the air inlet ports flanking the injector tip. If ECM has to open throttle beyond an acceptable value to get correct idle speed it sets this code.

Some scanners do not show all codes and may only show the ones turning on warning lamp. WHat scanner are you using?

coffeysm · Post by **coffeysm** » 24 Nov 2013, 00:46

I had the same exact problem as you and the car seemed fine, but the DTC kept coming back. Try cleaning it first when I took mine off it was full of crud (there is also a small hole that was packed with dirt). I ended up buying a used one from eBay for 50 bucks and the problem hasn't been back since.

thankswww · Post by **thankswww** » 29 Nov 2013, 08:48

Well, I took AACV off and gave it a good cleaning. Reset the fault codes, put it back on. Started the car and the code is still there, instantly. Car idles perfectly.

While I was in there, I checked the throttle body, and it was spotless.

I am using a cheapo scanner, nothing high-tech.

I guess I'll search for one on ebay, and hope that it's in good shape. A new one is over $160 plus shipping and import taxes. I wonder how the idle can be perfect if the valve us completely bad...

coffeysm · Post by **coffeysm** » 30 Nov 2013, 16:22

There a few of them on eBay now for about 55 dollars. Just search for: Volvo S70 V70 S60 Idle Air Control Valve IAC 1275634, 136800-1050 1999-2007.

I had the same symptoms as you and still can't tell a difference with the new part other then the DTC is gone.

tlarim · Post by **tlarim** » 18 Apr 2014, 21:44

Greetings. Hope this is appropriate place to drop this question.

I have 2000 S70 NA with possible AACV issue. Codes are clean. I discovered this issue when charging the battery (periodically I charge it to determine the status of the battery, charge/discharge state/rate) and noticed it seemed to recently be needing more charge than normal. While poking around the battery area, I heard and felt the faint vibrating related to the AACV (Volvo 1275634; 136800-1050; Denso 991208 on part). However, the engine was turned off and the ignitiion key was removed. So, that seems to ID the cause of the battery drain when car is off. Pulling the connector to the AACV stops the vibrating, which makes sense. Car idles/runs fine with the AACV connected or not. If I pull the connector and run a scan, it immediately has the 0505 pending. Plugging in the AACV connector back in clears the pending. But it gets better. When I disconnect the battery to remove system power with the AACV connected (vibrating with key removed), of course the vibrating stops. What surprised me was when I reconnected the battery the AACV vibrating was not present until I started the car, turned it off and removed the key - the vibration was back (no key). I removed the AACV, cleaned and lubed it with a bit of WD-40, blew it out and reinstalled it. I also treated the connector with DeOxit - didn't help. I hesitate to install a new Volvo 1275634 without the CEL being triggered by the 0505 indicating this is the likely problem. Soooooo...I'm stumped. Any words of wisdom out there?

Post by **VCA** » 19 Apr 2014, 08:04

Hi tiarim, the AACV is powered by the main engine management relay, 2/32 in the attached diagram. It's grounded (energized) by the ECU. The relay may be staying on either due to age or the ECU keeping it energized (or a faulty electrical portion of ignition switch)

tlarim · Post by **tlarim** » 19 Apr 2014, 22:44

Thanks. I pulled the system relay and tested it; it repeatedly closes and opens OK with 14V. Without the relay in the socket, the relay control contact sockets show about 3v with ignition off and 12.5v with ignition on. Key on-off consistently shows 3v off and 12.5v on. Installing the relay and checking the control contacts with key out shows the relay loads the control circuit such that the 3v (with no relay installed) drops to basically zero volts with the relay installed. So I'm seeing almost no voltage at the control contacts with ignition off and 12.5v with ignition on, until the first ignition on/start after the power is reapplied (reconnect battery or reinstall the relay), then the 12.5v gets stuck on, hence the battery drain at least through the AACV. If I pull the relay and reinstall it when the 12.5 v is "stuck" on, it returns the control voltage back to zero. I'm willing to put in a new system relay (found for under $40) just to see what happens. If problem goes away, great. Assuming that does not cure the issue, and knowing that with no relay installed the ignition switch seems to turn on and off the system relay control voltage properly, I'm still stumped. The farther back upstream this problem may be, the more it will probably cost. Hoping the relay will fix it, but am always willing to listen to good advice/ideas. Thanks again.

fars70 · Post by **fars70** » 23 Apr 2014, 01:06

thankswww wrote:Well, I took AACV off and gave it a good cleaning. Reset the fault codes, put it back on. Started the car and the code is still there, instantly. Car idles perfectly.

While I was in there, I checked the throttle body, and it was spotless.

I am using a cheapo scanner, nothing high-tech.

I guess I'll search for one on ebay, and hope that it's in good shape. A new one is over $160 plus shipping and import taxes. I wonder how the idle can be perfect if the valve us completely bad...

How do you clean the aacv, with throttle body cleaner? I wonder if its actually the energizing issue because something drains the battery w/o the key in the ignition as well.