Engine check light on 1999 V70 2.5D (UK)

With the curent cold weather, my (diesel) V70 (old shape) has been running
very rough for a bit after a cold start - so I suspected that the glow plugs
may not be operating.

This morning, before trying to start the engine, I checked all the relevant
fuses and relays in the main fusebox - to make sure that the fuses were
seated properly, and not blown - and the relay operated ok (when it was
removed and 12v applied to its coil).

In the course of my investigation, I was curious to know whether the
glowplug light on the dash indicates that the plugs are *really* on - or
simply that the system *thinks* they're on. I turned the ignition on with
the 15A fuse and relay removed, so that the plugs couldn't possibly
operate - but the light still came on!

I didn't find anything obviously wrong, and put it all back together - after
which the engine started and ran perfectly normally - with none of previous
roughness.

*However* the engine check light is now on, and refuses to go off. I suspect
that this was caused by turning the ignition on with the fuse out. The same
fuse feeds the emission control equipment. I guess that an error code was
generated, and will continue to turn on the engine check light until it is
reset.

Does this sound likely, or is it indicative of something more sinister? Is
it a trivial (and cheap!) job for a dealer to reset it? Presumably there
isn't a DIY way of doing it without access to OBD-II equipment?

TIA.

 

How long has it been on? I believe the Volvo ECUs are designed to turn the
light back off if they don't detect the same fault again within a certain
combination of time, miles and starts.

 

In an earlier contribution to this discussion,

It's done it for 24 hours, during which I've done about 6 starts and 25
miles.

Are you suggesting that it may sort itself out after a few more
days/starts/miles?

 

If the problem is gone, it should reset itself after 3 complete check
cycles - on my '98 this is 3 trips to or from work, which is about 25
miles and 30 minutes. Short trips do not allow complete check cycles
and won't contribute to turning off the light.

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

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

 

In an earlier contribution to this discussion,

Thanks- that's encouraging!

Do you have a feel for the minimum length of trip (time/distance) which
would count? [Presumably less than 25 miles, but more than the 6 mile trips
which I have done recently].

 

The heater plugs won`t affect running after starting.They are only
energised for a few seconds prior to starting.My wife`s 850 2.5 TDI`s
heater plugs are not working although the light still comes on as
normal,but the engine starts first time.On the other hand one of our
vans (Peugot) whose heater plugs are working perfectly will not start
on a cold morning even with a burning newspaper held in the manifold.
regards,Mark.

 

I have a 1999 V70. The ETS (Electronic Throttle Control System) light comes
on after the car hasbeen running for about 15 minutes. The car runs
smoothly. My mechani says the electronic brain needs to be replaced or the
ngine will start to run rough then perhaps have trouble starting. Any
suggestions for next steps I should take? Do the Volvo dealers have a
diagnostic machine which specifically diagnoses the problem?

 

The dealer has a computer with special software and a proprietary interface
device to read diagnostic information from your Volvo. It will tell the
technician which signal caused the fault light to come on, and if he's
competent, he'll be able to trace that signal back to the faulty component.
(The dealer will typically expect you to be very generous in compensating
him for providing this service.)

In ETS, the ECU (engine control unit) gets position signals from a pair of
sensors attached to your accelerator pedal and uses that information to
generate a signal telling the throttle unit on your engine to adjust its
position accordingly. I would suspect moving parts, like the position
sensors, before electronic parts like the ECU. Since everything appears to
be working normally, it may be that one of the position signals is faulty
and the ECU is complaining about the lack of redundancy.

 

In an earlier contribution to this discussion,

Not so! The following is the description given in VADIS of the glowplug
operation on the 2.5D engine:
__________________
Preheating
If the ignition is switched on when engine temperature is below +5 °C, the
glowplugs are activated for a period which varies with engine temperature
and atmospheric pressure. The glowplug indicator lamp on the dashboard
indicates that preheating is active. Preheating shuts off when the engine is
turned by the starter motor.

Stand-by heating
After preheating stand-by heating is activated for up to five seconds. This
corresponds to the time between the glowplug indicator lamp going out and
the engine starting. This makes the engine easy to start even if it is not
started as soon as the indicator light goes out.

Start heating
Start heating is activated for up to 30 seconds each time the engine is
turned over by the starter motor, if the engine coolant temperature (ECT) is
below +30 °C and engine speed (RPM) is below a given threshold. Start
heating facilitates engine starting even when it is not entirely cold.

Post-heating
Post-heating starts when the starter motor stops turning the engine.
Duration depends on engine temperature, engine speed (RPM) and quantity of
fuel injected. Post-heating is always shut off when engine speed (RPM)
exceeds 2500 rpm, irrespective of engine temperature and the quantity of
fuel injected. Post-heating is always activated even if preheating has not
been activated. This improves combustion which reduces noise levels,
improves idling and reduces exhaust gas emissions. Post-heating also
improves idling at extremely low temperatures.
_______________

 

Each time my V40's MIL light has come on, (three times that I can remember)
it's gone off again in about three work days. I drive 25 miles each way to
and from work and usually drive a mile or two for lunch. This is strictly a
guess, but there's probably something built into the algorithm to allow it
to decide that the light should turn off after some number of short trips or
even a single very long trip. It would make sense to have it that way to
accommodate different use patterns, but all I can say for certain is what
I've actually seen for myself, so don't take my guess as anything remotely
authoritative. At any rate, I'd say that if your light doesn't go off within
a couple of weeks under just about any driving conditions, you probably have
a real fault somewhere keeping it on.

 

I'm not aware of the minimum trip, but I know it requires some constant
speed driving for several minutes, and some periods of idling after
warmup where the A/C does not come on. It seems that my trips to and
from work are ideal for this.

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

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

 

Just ran across this in VADIS for my V40. (I'm much too lazy to check and
see if it applies equally to other cars.)

"If a fault disappears for any reason after the diagnostic trouble code
(DTC) has been permanently stored in the control module, information about
the fault remains in the control module for a while. For each diagnostic
trouble code (DTC) stored, a counter records the total number 'fault-free'
operating cycles since the diagnostic trouble code (DTC) was stored. If the
control module does not register the fault after 10 completed operating
cycles, the diagnostic trouble codes (DTCs) are erased automatically. They
are 'self-erasing'."

"An operating cycle is defined as where the ignition has been switched off
and then on again and the vehicle has then reached a speed in excess of 30
km/h. The ignition must have been on (or the car driven) for longer than 5
minutes."

 

In an earlier contribution to this discussion,

Thanks, that's useful. I have a copy of VADIS, but haven't come across that
information for my V70. Can you please tell me how you got to it for your
V40 - and I'll follow the same route?

 

Selected Function Area: Electrical System
Selected Information Type: Design and Function
Topics: 38 Instrumentation
Diagnostic Functions ->
Combined instrument panel diagnostic functions ->
Diagnostic trouble codes (DTCs)

 

In an earlier contribution to this discussion,

Thanks. I've found the information you referred to for the V40 - but
unfortunately, the equivalent V70 section doesn't contain any of this stuff.

 

Are you using a politically conservative newspaper or a liberal one?