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[holey head]

if it only does it on a warm start i think it's more likely crank sensor, somebody else had same prob think it was grumpy. is it limiting at 4500 rpm???

[magnul]

In the beginning it was only when warm. After a few days it became permanent. A new crankshaft sensor is on its way from the uk. Dunno if it will sort the problem, but I guess the crankshaft sensor would fail soon anyway, so I'm being a bit proactive.

[magnul]

I replaced the crank sensor. Didn't solve the problem, although the engine appears to run a bit smoother after the change.
Got a mechanic to check cam belt timing and tension, all in perfect order.
Bought and fitted the modded sensor today, but fault is still there

Any advise on what to do next? I'm getting a bit desperate now.

[holey head]

hi again,

check that you have made connections good on new wiring loom on modded sensor. and that none are shorting. seems daft but it does happen. try reading codes again and see if you getting same codes. is engine limiting at all???

cheers steve

[magnul]

I've just re-checked the continuity, and alle the connections from ECU connector to sensor connector are good.
From what I've read this sensor should operate with a high frequency reference signal (100-180kHz) of unknown magnitude. As the modded sensor gave me some points to measure at, I tried to measure AC volts from red/white cable (AC signal from ECU) vs battery negative with a Fluke. The signal was only a few tens of mV. Tried the frequency-mode (not used to working with AC), and the frequency was a few tens of kHz, but basically just noise/background. Don't know whether this signal is within the capabilities of my Fluke, but I'm a bit concerned that the AC-thing in the ECU is broken. I think I can borrow a decent oscilloscope from work, but I'm not quite sure what to measure, and how waveforms should be. My only reference is this page: http://www.picotech.com/auto/cam_ac.htm

[magnul]

Now I've soldered the sensor into the loom closer to the ECU. EML still on and still in limp home mode.  
TB wrote in a related thread:

Unplug crank sensor, see if symptoms are similar....
 
 
Other thinks to check - try switching on ign, leaving 20s, then starting. Also, try crank for 5s WOT, then start normally...

Should the crank sensor be disconnected with engine running or before start?
What would I learn from the above tests? I guess cranking at WOT would be to clean out any fuel from leaking injectors, but could that throw up a fault code?

[Grumpy]

It is possible that one of the cables to Cam Sensor is earthing and
destroying your Cam sensor signal.

The cam and crank sensors share a common earth, so disconnect the
cam sensor plug to break the earth connection from pin 3 on the
 crank and cam sensors to Pin 2 on the ECU.

Now check that there is no connection to Earth on Pins 1 & 2 on the Cam
sensor plug or Pins 4 & 22 on the ECU.

As a final check, check that the earth connection is actually intact by
checking between Pin 3 on the Cam and Crank sensor plugs and Pin 2
on the ECU and Earth.

No guarantee this is the fault, but assuming you haven't fitted a new duff
cam sensor, or the common earth from the crank sensor isn't duff, then
you have to check the wiring again from a different perspective.

'Sparks3ks' will be probably be able to advise better on this approach as
he actually is a 'Sparky'.  

[magnul]

Thanks. I think I've done all the things you mention, and could not find any earth errors within the cable harness. I thought I found a problem yesterday when checking all the connections at the ECU connector, as I got continuity between ground pin and crank AC signal pin, but soon realised that it should be a connection there. This connection was in the sensor, not harness (unplugged sensor and rechecked). I'll try to measure resistances on new and old crank sensor and see if they match. The old sensor was changed before it failed.

[Grumpy]

This connection was in the sensor

Yes, both Cam and Crank Sensors are connected to Earth due
to capacitors linked within each sensor, but both Earth cables,
from each sensor, also link together to form a single common Earth
to the ECU. Whether this is at the ECU or within the Harness to the
ECU, I don't know.

When you disconnected the Crank Sensor Earth return, you would have
broken the Earth return path from the Crank Sensor, but not the
Cam sensor Earth return.

When you originally started this thread you've been checking for faults on
your Cam Sensor and associated wiring, but now you're talking about
the Crank Sensor wiring. The only common wiring to these 2 sensors
is the Earth return paths on Pins 3 at the Cam and Crank Sensors and
Pin 2 at the ECU. If you had a fault in this circuit I would have thought
that you would have got error codes for the Crank and Cam Sensors.
But you say you're only getting a Cam Sensor code.

When you disconnect the harness at the ECU, and the Cable connectors
at the Cam and Crank sensors, you say you've checked the Harness
between the two and can find no faults.
With the ECU and Cam and Crank sensor plugs disconnected, have you
checked the cabling for faults between the plugs and the sensors?
For instance, are you getting an Earth return on any of the cables, when
you shouldn't do because the Crank and Cam plugs are disconnected and
thus breaking the Earth return circuits?

Sorry if I'm stating the bleeding obvious here, but I don't know what
checks you've carried out.
No offence intended.  

[magnul]

Can't blame you for not knowing what I've done during my many hours of fault finding:)
The common earths of the two sensors appear to be at the ECU side of the loom.

The reason why I'm talking about the crank sensor is that browsing all kinds of forums have told me that cam and crank sensors are often related. Now I'm pretty sure that there's nothing wrong with my cam sensor or wireing. The only common wire is, as you say, ground at ECU pin 2. However, I'm wondering whether crank sensor problems appears to be cam sensor problems, as the crank signal is the primary trigger and discrepancy between the two signals can be interpreted by ECU as cam sensor fault. This is why I changed the crank sensor a couple of weeks ago.

With the ECU and Cam and Crank sensor plugs disconnected, have you
checked the cabling for faults between the plugs and the sensors?
For instance, are you getting an Earth return on any of the cables, when
you shouldn't do because the Crank and Cam plugs are disconnected and
thus breaking the Earth return circuits?

Yes. I have checked from ECU plug both with sensors connected and disconnected. Earth and shilding cables are grounded, whereas the others are not when sensor plug is disconnected. To summarise I've performed all tests I can think of on the electrics and found nothing wrong.
I have tried to start the engine by rolling down hill (someone claimed tired starter could cause problems), but to no luck. I have not yet tried to start the engine without aux belt (is it ok to do for a few seconds?) as some have claimed that interference will be caused by ignition system, not alternator.

[Grumpy]

Yes. I have checked from ECU plug both with sensors connected and disconnected. Earth and shilding cables are grounded, whereas the others are not when sensor plug is disconnected

If you've checked from the ECU Plug, then the plug would have to have been disconnected
for you to check. If the ECU plug was disconnected then the Earth cable should not have been
grounded.
Or am I misunderstanding what you are saying?

Also, although you probably have if you've done loads of checks, have you actually
checked the cabling between the sensor plug (not the ECU plug) and the sensors
when all plugs are disconnected to isolate each circuit?

As said, you probably have, but you didn't actually state this and I'm just checking.

[magnul]

With ECU plug off I use ECU connector pin 2 as earth. With ECU connected I use battery negative as earth to check earth connection for both what should be connected to earth and those that shouldn't.

Sorry that I'm not able to make everything clear. I express myself a bit better in Norwegian

[Grumpy]

Forgot to add. The reason I'm concerned that you may have an Earth
when you shouldn't, is that although we draw our Electric circuits showing
the flow from +ve to -ve, electons are negatively charged and actually
flow from -ve to +ve. That's why you get some weird results, for instance, when wiring
up tow bars.

No idea if you know all this, you may be an electrical genius for all I know  
But plenty of folk reading this thread aren't.  

[Grumpy]

I express myself a bit better in Norwegian

And my I say that you express yourself much better in English
than I would ever do, trying to speak Norwegian.  

[magnul]

No idea if you know all this, you may be an electrical genius for all I know  

I'm pretty retarded when it comes to electricity, but being and ELECTROchemist I'm pretty used to fault finding at the lab. A bit embarrasing that I don't know more about the electro-part of my profession...
However frustrating this particular fault it, at least I've learned to read wiring diagrams in Hayes the last couple of weeks:)