1998 s70 MAF ECU connector location

goVolvo · Post by **goVolvo** » 25 Jan 2015, 06:31

Hi there,

This car has MAF input low problem and I want to check if the 12V supply is all right. Where is the connector on ECU side for the MAF wires? I found wire diagram here but don't know where the ECU terminals are.

Thanks a lot!

Post by **Ozark Lee** » 25 Jan 2015, 09:03

You can get the factory wiring diagrams with all of the pinouts here:

http://www.volvowiringdiagrams.com/

The pagination is all screwed up but they are pretty much all there.

...Lee

goVolvo · Post by **goVolvo** » 25 Jan 2015, 16:07

Ozark Lee wrote:You can get the factory wiring diagrams with all of the pinouts here:

http://www.volvowiringdiagrams.com/

The pagination is all screwed up but they are pretty much all there.

...Lee

Great info. Thanks. I need to know where to locate the ECU terminals or harness in the car so I can trace the 12V supply to the MAF. The diagram I got one here.

Post by **Ozark Lee** » 25 Jan 2015, 17:37

If you are asking about the physical location of the ECU it is in a plastic box on the right hand side of the car, just behind the windshield washer fluid bottle. There should be two modules in the box, one is the ECU and the other is the TCU for the transmission. The modules slip right out after you move the retainer lever. You can't really test the ECU connector with the module in place without a breakout box which is unbelievably expensive.

The +12 volt to the MAF doesn't come from the ECU however, it comes though the master fuel system relay and is tied to the same circuit that provides power to the injectors, the idle air control valve, and a host of other sensors.

...Lee

goVolvo · Post by **goVolvo** » 26 Jan 2015, 12:26

Ozark Lee wrote:If you are asking about the physical location of the ECU it is in a plastic box on the right hand side of the car, just behind the windshield washer fluid bottle. There should be two modules in the box, one is the ECU and the other is the TCU for the transmission. The modules slip right out after you move the retainer lever. You can't really test the ECU connector with the module in place without a breakout box which is unbelievably expensive.

The +12 volt to the MAF doesn't come from the ECU however, it comes though the master fuel system relay and is tied to the same circuit that provides power to the injectors, the idle air control valve, and a host of other sensors.

...Lee

I am looking for the physical connectors in the car so I can trace down the wire or connector if 12V is not delivered to MAF pin3. Eg. I want to find where the 12V is OK from the master fuel system relay, and measurable connectors on the way to MAF pin3. I still need to double check with inserted paper nail/safepin/nail method though.

Post by **Ozark Lee** » 26 Jan 2015, 16:09

The schematics that you downloaded have junction points called out and then, if you dig deep enough, you can find some pages that graphically show where those points should be located. Under the hood many of them are actually splices inside of the loom and they are tough to check.

If I were in your situation I think I would see if there is battery voltage on the green injector wires as well. If you have no voltage there and the idle air control valve isn't buzzing I would focus on the master fuel system relay which is the gray relay on the fan shroud - left hand side of the car.

That relay itself isn't usually much trouble but the wiring to the connector to the relay is a known troublemaker.

...Lee

goVolvo · Post by **goVolvo** » 29 Jan 2015, 00:16

I looked at the wiring diagram and hopefully I am reading it correctly.

The engine management is Motronic4.4 as for 1998 S70 N/A and also turbo.
MAF Pin3 is connected through junction 23/11 on harness 24/43 Pin3, which is from fuse 11B/2 after the main relay.
I looked today, MAF Pin3 only has 0.3V for some reason. If current wire is somehow broken, I'll try to fly-wire from harness 24/43 to MAF pin3 directly. Should be straightforward. See attached.

goVolvo · Post by **goVolvo** » 31 Jan 2015, 20:07

Oh, my goodness. I was going to jump a wire from fuse box to the MAF connector since they are so close. When I peek into the wires in the rubber tube on the connector, PIN 3 and 1 are actually cut off, and stay quietly in the tube. Looks like previous owner was driven crazy by it and did this and just leave the engine light on, and ECU runs with default number.

My work is easy now. Got a small clamp-on wire connector, connected PIN 3 wire. But there is no more space for another connector in the tube for PIN 1, so I soldered PIN 1 wire together. It is GND and stays in the tube, quite comfortable.

Now I see the voltage are good, 11V to 12V before starting engine, and the BOSCH MAF insert worked! So MAF problem solved. Only problem is now that idle RPM is not stable. Don't know why.