Anyone know the pinout on the '98 S90 ECU. From what I know it's Motronic 4.4 -- specifically I'm looking for the two O2 sensor inputs, but would be nice to be able to grab +12V and ground also. Anyone?

 

What are you trying to install?

 

I'm anticipating one or both O2 sensors may be bad when I start this engine back up - have built a two-channel O2 monitor that I wanted to install in the cabin. Just too messy trying to graft a connection to the sensors under the hood.

In the meantime, you may be able to help with the more present problem with the rebuild. Everything is back in and double-checked. What I have now is a classic no-start where either the CKP or CMP are bad -- injectors are not firing, no spark, and the tachometer is dead flat while cranking.

The camshaft position sensor - although it looked pretty fragile when I pulled it out is presenting a very nice square wave at the mating connector on the backside of the head.

The crank sensor I am less sure about - have it unplugged and watching it on an oscilloscope. Should I see a pulse (I know it is not a square wave) on every revolution of the crank or more frequently? (e.g. per tooth???) I need to recheck the resistance - I'm seeing neither I think.

While I've got you (as you seem to be the only one in the know!) does this model ('98 S90) also have the immobilizer function - and since the battery has been out for two-months now -- is that something I should be chasing as well - assuming I can coax a signal out of the CKP?

The cylinder head rebuild was enjoyable and educational for me. Although I'm very comfortable with electrical things - lacking the manuals I'm pretty lost here.

Thanks in advance - anxious to hear back from you!

 

UPDATE - and very puzzling still. Found and purchased the service manual from ALLDATA. Have rechecked the CKP at the ECM and see waveform of about .4v p-p that looks like it's related to engine cranking RPM. That seems to be in line with expectations for a non-Hall Effect sensor. But I don't know what the ECM expects.

Also checked the following and confirmed good:

CMP signal at the ECM
Function of Fuel System Main Relay.
High-Side voltage on the FIs and Ignitors while cranking. So Fuel System Main and Ignition Coil relays seem to be functioning.

Any other inputs that would keep the ECM from cycling the low side lines to the FIs and ignition discharge modules while cranking?

ECM was in working order when I garaged the car in February and since it still seems to know to release the fuel pump relay a couple seconds after bringing the rail pressure up - it's working somewhat.

 

One question when you removed the intake did you take a bolt out from the bottom?
Looking from the bottom there is a plastic loom that runs under like where the nut for the intake mount is. There is actually 2 ground wires there. If they are off they will show all the signs you have.

Have you read all up on the O2 sensors on these cars?
They only read 1/2 a volt to 1 volt.
Easiest way I have found to tap into them is look at a wiring diagram for the Signal wire. Then find a 960 in the junk yard and cut the O2 plugs from the car. Cut the sensor wires and harness car side. This way you will have 2 plugs. The splice the wires together this way you will make a plug you can put inline. When you splice together add a extra wire on your signal wire. Then you can connect the meter you made to it.

Make it so it looks like this.


Yes they have an immoblizer but it cuts the starter.

 

I removed the nut holding the bushing on the bottom of the intake manifold to the bracket - is that the same nut that holds the ground wires that you mention??? I didn't put that back on yet - because it is rather difficult -- that'll teach me a lesson if it turns out to be one and the same bolt!

 

No it is not. But if you crawl under there and look up towards there from the back side of the crossmember you should see the wires.

Also what condition was the single wire at the back of the head that goes to nothing?
Make sure that is not grounding out either.

 

I don't remember removing anything other than the nut on the bottom of the bowl. I'll get under there and check to make sure that those lugs are grounded.

The test point on the wire loom at the back of the head is in reasonably good shape - will double check but I think that's Ok.

I have ScanTool and can pull throttle position from the diagnostic port, and get Engine RPM of 30 while I'm cranking (seems odd) Only other thing I see is rather odd - says that Timing Advance is 65degrees. I removed the reluctor plate from the exhaust cam to replace the seal - but am sure I got that back in the slot correctly. Do you think this info from the diag port is enough evidence that the ECM is alive?

Thanks much - really appreciate your expert help!

 

You might want to double check the plate and make sure it is on straight.
After you remove the cam sensor look straight down the back of the head and make sure it is straight and not off center.

Did the screw seem hard to put back in?

 

Removed the cam timing plate. It appeared straight, but when I placed it back on the end of the shaft I realized it would engage the shaft in two places, 180deg out from each other. When I had the camshafts out of the engine - I removed the plate and had somehow convinced myself that the tangs on the plate were slightly off center-line and that the plate would only go on one way. If that's true - I could have forced it back on the wrong way at some point.

So I flipped it, still no start - but the diags now say 6degs of timing advance which seems much more inline with what I expected. Pulled the battery cable now, and going to let the ECM rest for 30mins to see if it wants to start the engine later.

 

Hopefully that is it.

 

Still no spark. I removed the intake manifold again to check those two ground lugs that you mentioned earlier. They were in place, I removed, cleaned and reattached. Put everything back up and still nothing.

Still not convinced that the crankshaft speed sensor is really working. I see a signal at the ECM and its the right waveform but still less than .5v AC. The tech manual says 1.8v AC at idle. I know that 750RPM would produce a higher voltage.

The tachometer needle is dead flat and the diag port is reporting 30RPM while cranking - tomorrow I'm thinking of building a small amp to bring the signal level up and see where we go from there. Running out of ideas.

Also noticed the supply voltage at the ECM while cranking is around 10.5V - that seemed a little low. Topping off the battery overnight. Thanks again for keeping an eye here!

 

Did you check for spark on all the coils?
And same on all injectors?

The power stages on the side of the intake control the cylinders as well. One side is 1-3-5 and the other is 2-4-6. Any possibility you pinched one of the coil leads and it is shorting out? All the fuses good?

 

all fuses pulled and checked. Verified +12V on the high-side off all injectors and ignitors. But the low sides are not being pulled low - nada. It looks to me like the ECM doesn't think the engine is turning and doesn't feel the need to fire anything - or to wiggle the tach line.

 

OK just running out of ideas and just throwing things out there.

 

i'll let you know how the amp trick works. If that works I'm in for a new crank sensor. If not I may be shopping for a new ECM - running out of ideas myself! )

 

Happy to report that the AMP did the trick - the CKP which looks like it's working wasn't sending levels high enough to trigger the ECM. With the AMP, which I placed between the CKP and the input to the ECM, the levels are now much better and the car starts. I have a theory on how I turned a perfectly good CKP into the troublemaker that it's become - if you're interested. (The problem started with a piece of information that indicated the coolant temp sender is on the rear of the cylinder head. The service data suggests the same in several diagrams. )

Will report more on this as progress is made. Thanks again for chiding me along. I didn't let the car run very long -- but I can tell you that it is running lots smoother than in February when you told me I had a burned exhaust valve on #1.

Sweet!

 

There was only a coolant temp sensor in the back of the head on the older cars.

The newer cars did not have them.

I hope it goes well from here.