850 Lambda Light.....

My 2.0 Litre 10V 850 has covered 115,000 miles......

Friday morning I do my ususal run (40 miles) to work, all is well. About
lunchtime I had to move the car to let a colleague out the car park. So The
car ran for 5 minutes, again all was well.

On starting the car to go home at about 2pm I notice that the Lambda light
is on. The car seems to be running normally.

I drove home.... (40 miles again) Let the car cool overnight, it starts
fine..... Left the car alone on Sunday 'till about mid-day Monday. Again
it runs normally with no other sign of ill-health..... It's very cold and
damp here so the car's starting under difficult conditions. It idles well
right the way through the temperature range... Cruises happily, drives fine
in city traffic.... Did maybe 20 miles yesterday...

I have a few questions.....

1) This is a 'check engine' light yes? Which indicates the ECU found an
error on one of the sensors?

2) If an intermittant (or spurious) fault developed giving rise to a freak
error on starting, would this permanently set the lambda light on? Or would
the light clear when the error cleared (I'm thinking here the short 5 minute
run may have left unburnt fuel somewhere)

3) My car has the data connector in the centre console. I'm an electronics
engineer by training, is there a schematic for a fault code reader online or
even a device that would allow me to reset the light....

4) Assuming the light would clear itself on curing a fault, what's the most
likely cause of the lambda light coming on....

I've left the Volvo at home today; don't want to do any more damage.......

 

"LaoFuZhi" <the.real.address
thing.not.too.hard.to.work.out> wrote in message

I would guess a strange spurious fault has upset the ecu and its lit the mil
lamp, especially as you say the engine is behaving as normal. Probably no
fault present, but the lamp will remain lit until you plug in a code reader
to the OBD socket on center console and read any codes, and cancel them. You
can then reset the light.

Look for an EFI specialist nr you in the yellow pages, ring them to check
they are familiar with the Fenix 5.2 on your car and have them check and
then cancel the light. If however it re-appears then its time to delve
alittle deeper.

Just for your information- had you performed the start-run-stop act from a
cold start and only ran it for say 1-2 mins, when you come to re-start you
would probably have failed. The 5 cylinders are very prone to flooding when
in this scanario.

Tim..

 

If your 850 is year 96 or later it will be with OBD2 interface.
some good information on hardware for the interface can be found on
http://www.andywhittaker.com/

Software is available from lots of different sites, also for free or
shareware.
http://www.onboarddiagnostics.co.uk/volfcr/demo.htm
has a demo software that will work for you to see if your interface is OK.
I think the hardest thing to get is the connector that goes into the data
link connector in the center console.

Per Hauge

"LaoFuZhi" <the.real.address
thing.not.too.hard.to.work.out> skrev i en meddelelse
news:buikvf$9gr$...

 

I would guess a strange spurious fault has upset the ecu and its lit the
mil

That's very much appreciated information Tim.

The plot thickens somewhat. I found myself having to use the car today. All
was well on the road in however fun started on the journey home.....

About 90 seconds after start up (engine stone cold) the temp gauge suddenly
rose to it's normal (half way position). This persisted for 20 second or so
when it indicated cold again, and continued to behave normally as the car
warmed up....

All was well 'till about 20 minutes into the journey. I was in a
contra-flow section of the motorway when the car seemed to 'die'. At this
the temp gauge indicated ZERO!......... Fortunately this corrected itself
after about 10 seconds and the journey carried on as normal......

I'm now guessing the light is on because of a temp sender problem. What I'm
a little surprised at is that the engine would stall for lack of input from
a temp sensor! I'd have hoped the ECU would have had a 'fail safe' mode for
such an eventuality!!!

Obviously I'll be using the other car for sure tomorrow!!!! I should get a
look at the volvo over the weekend....

So any additional clues, tips or info anyone can come up with would be very
much appreciated....

 

Thanks for that Per,

My car is indeed a later model fitted with the OBD2 interface.

I'll email Andy directly. I am though a little confused. I had assumed that
the interface on my 850 was peculiar to Volvo. Andy's page seems to suggest
that OBD II ..as fitted to the 850 is some sort of ISO standard???

May I assume this is the case?

 

"LaoFuZhi" <the.real.address
thing.not.too.hard.to.work.out> wrote in message

It definately sounds like you have a possible fault with the coolant temp
sensor, although the ecu does have strategy built in if it suddenly gets
unexpected signals from the CTS and the temp gauge shouldnt be moving about
so randomly. I'm alittle concerned that you have a deeper problem, but check
carefully the CTS and wiring first- make sure its not chaffed on or around
the powersteering pump. Then oik it out, suspend in a saucepan of iced
water with a DVM hooked up to both outputs and check its resistance as you
heat the water. There shouldnt be any jumps or glitches.

Tim..

 

OBD-II is a requirement for all cars sold in the United States from
1996. There are several different communication protocols within the
standard, but most readers will handle all the protocols. There is a
mandated list of codes that are required, and also different, unrequired
codes can be manufacturer specific. You can find out lots by searching
on OBD-II on the internet.

--
Mike F.
Thornhill (near Toronto), Ont.

NOTE: new address!!
Replace tt with t (twice!) and remove parentheses to email me directly.
(But I check the newsgroup more often than this email address.)

 

I wonder if you have the common intermittent ignition switch electrical
problem. It can cause all sorts of strage behavior. On my 850 it cause
most of the instruments (including the speedo) to go off and on
intermittently.

Your situation sounds different, but see if wiggling the key in the ignition
changes anything.

You can read about the repair procedure at this excellent resource (I have
used several of their 850 how-to articles):

http://www.volvospeed.com/Repair/ignit_switch.htm

John