OBD2 on 10-valve V70s (again)

[Chris_Rogers]

My advice is to get yourself a multimeter if you have not got one. Also get an insulaton piercing croc clip (or use a pin) so you can get onto the wires at the sensor end without cutting them.
Remove the ECU then check the signal wires from sensor to ECU socket for continuity. Use the wiggle test on the loom while you do this and watch the meter. Expose as much of the loom as you can.
Then test for insulation resistance between cores and ground repeating the wiggle test.

[ascott1]

>...check the signal wires from sensor to ECU
>socket for continuity. Use the wiggle test on the loom while
>you do this and watch the meter. Expose as much of the loom as
>you can.

Tried this, but having trouble exposing any of the loom, can anyone advise on access? Posted some photos at URLs below. Got the offside headlight out to get at conduit near base of ECU box, but still can't get the lid off any of the conduit (looks pretty dirty and undisturbed since 98, can pop 4 clips holding first box section from ECU to curve, top lifts a little but doesn't come off). The conduit curves under the front plastic panel which holds both headlights. Is it necessary to remove this big panel and both headlights? Or should it be possible to disconnect the loom from a connector at the base of the ECU. (Can't seem to move it). There are concertina sections of conduit between rectangular and curved sections, but can't seem to split them. If I had a scrap loom to look at, I'd have a better idea what to look for, but nearest one seems to be in Dumfries (V70 2.5 diesel), 2 hours drive each way.

Dark night stopped play for today, may be next weekend before I can get back to it. Car still starts as poorly, no worse, after reassembly.

http://www.volvoclub.org.uk/photopos...cat=500&page=1

http://www.volvoclub.org.uk/photopos...cat=500&page=1
and

http://www.volvoclub.org.uk/photopos...cat=500&page=1

[ascott1]

No good news on this loom access. I found an independent tester with Bosch diagnostic kit, 40 miles away, who tells me "wires OK", but there's no sign of his having opened it. He got the car to miss-fire during starting with a good cps signal "going into the ECU" but I don't see how you could trace the signal to the ECU input pins without opening up the loom.

[cootuk]

Is the cam sensor a genuine part?..just a thought...it might be giving peaks, but are they the peaks (frequency, voltage) the ecu is expecting?

I know some cars will run with the cam sensor disconnected (they just assume the reading based on other factors and limit the revs as well?) but I thought the 850s cut the fuel supply if the CPS malfunctioned - I believe that in an accident where the fuel lines are severed the fuel pump would be shut off rather than the ecu merrily sensing no engine rotation and merrily pumping fuel everywhere.

[ascott1]

>Is the cam sensor a genuine part?..just a thought...it might
>be giving peaks, but are they the peaks (frequency, voltage)
>the ecu is expecting?
Yes, replaced 12 months or so ago. The engine always ran fine once started, and started fine, first time, most of the time. Are there any specs on required voltages and pulse widths? I hear the device is a hall sensor detecting a cutout on the end of the camshaft, my mechanic tells me the gap is there and doesn't seem damaged.

>I know some cars will run with the cam sensor disconnected
>(they just assume the reading based on other factors and limit
>the revs as well?) but I thought the 850s cut the fuel supply
>if the CPS malfunctioned
That's what I've been told too, though there's also the crankshaft sensor signal which can support fuel cut-off. I replaced the fuel pump relay in case of dodgy operation during starting, no effect.

[ascott1]

Thanks again for peoples' suggestions for this V70 2.5 10-valve problem. To round this out, the Bosch diagnostic guy mentioned earlier in the thread, sent the ECU off to a repair specialist who returned it reporting a faulty Texas microprocessor and no part available. I was told the car was ready to collect, went to get it but it wouldn't start, they diagnosed missing signals from the ECU and everyone denied liability. Eventually they towed it for free to a Volvo main dealer who said the ECU was damaged and got me to request fitting a new one <sigh>. None of the problems with cam sensor codes or poor starting returned after that, in several months' running. The car continued to show other early V70 problems (suspension/driveshaft play though not enough to prevent getting an MOT, related poor tyre life; bumpy ride; persistent oil consumption; expensive parts; misted windows in wet weather; poor paint on plastic bodywork; etc). I disposed of it without mentioning VOC, fortunately at not too great a financial loss, it still looked quite nice overall. Don't think I'll buy another one.