Crankshaft position sensor

Spice Burger · 13-09-2015 12:46pm #1

Good afternoon,
I have an issue with a 04 Ford Fiesta Mk6 & would be grateful for any advice / guidance.
While the engine is running the tach/ rev meter keeps dropping to zero and coming back to live again . The engine light sometimes comes on when this is happening.
I can go months & all is OK then problem suddenly re-appears.
The fault code from engine consistently shows the crankshaft position sensor as the culprit which I have had replaced twice.(a year ago and this month)
The garage said all connections & wiring to the sensor are sound but the problem persists.
I would appreciate any advice / opinion on the above please.
Regards Mike.

PukkaStukka · 13-09-2015 2:55pm

Were either sensor physically damaged when they were removed?

Spice Burger · 13-09-2015 3:16pm

PukkaStukka wrote: »

Were either sensor physically damaged when they were removed?

Thanks for reply.
I am not sure..I will have to call and ask when they open tomorrow.Changed latest sensor on Friday and the tach failed again this morning. :-(

Do you suspect the sensor could be catching fly wheel?

PukkaStukka · 13-09-2015 3:48pm

Spice Burger wrote: »

Thanks for reply.
I am not sure..I will have to call and ask when they open tomorrow.Changed latest sensor on Friday and the tach failed again this morning. :-(

Do you suspect the sensor could be catching fly wheel?

Yes, there have been some issues of clutch debris jamming in the flywheel swiping the sensor, and some with engines having excessive crankshaft float. I'll see if I can dig up a link....

What engine does yours have?

Spice Burger · 13-09-2015 3:54pm

PukkaStukka wrote: »

Yes, there have been some issues of clutch debris jamming in the flywheel swiping the sensor, and some with engines having excessive crankshaft float. I'll see if I can dig up a link....

What engine does yours have?

Your a gent...Just the basic 1.25l lx model.

PukkaStukka · 13-09-2015 4:00pm

This by no means is the same issue you have, but IF the sensor is damaged then this might be it

http://www.bba-reman.com/forums/topic70558-1-1.aspx

martinr5232 · 13-09-2015 4:07pm

Those sensors dont really give any trouble i cant remember ever changing one.
Instrument clusters give trouble on those fiestas but you would need a proper diagnostic done before replacing any parts.

Spice Burger · 13-09-2015 4:17pm

PukkaStukka wrote: »

This by no means is the same issue you have, but IF the sensor is damaged then this might be it

Thanks Pukka.A couple more Avenues to explore.Cheers.

Spice Burger · 13-09-2015 4:24pm

martinr5232 wrote: »

Those sensors dont really give any trouble i cant remember ever changing one.
Instrument clusters give trouble on those fiestas but you would need a proper diagnostic done before replacing any parts.

Thanks Martin.

2 different garages both changed the same sensor a year apart.

Would a bad instrument cluster give out a fault code relating to the crankshaft sensor even if the sensor is 100% ?

martinr5232 · 13-09-2015 5:58pm

Spice Burger wrote:

Would a bad instrument cluster give out a fault code relating to the crankshaft sensor even if the sensor is 100% ?

The sensor is only one part of the circuit it could be a wiring fault a pcm or the cluster.

The garages you are going to more than likely see a crank sensor fault and replace the cheapest part on the off chance it will fix it instead of actually diagnosing the fault.

As i said more than likely its the cluster that is faulty because if it was a sensor you would be having starting issues which i presume you are not.

PukkaStukka · 13-09-2015 6:24pm

martinr5232 wrote: »

The sensor is only one part of the circuit it could be a wiring fault a pcm or the cluster.

The garages you are going to more than likely see a crank sensor fault and replace the cheapest part on the off chance it will fix it instead of actually diagnosing the fault.

As i said more than likely its the cluster that is faulty because if it was a sensor you would be having starting issues which i presume you are not.

Cranks sensor can cause running as well as starting faults. The garage obviously saw a crank sensor fault code and that's what they plumped for it. Why would a faulty cluster cause a crank code?? If the cluster was causing the car to cut out then the cluster itself should generate its own code. That obviously depends too if the scan tool the garage used was a suitable one for reading those codes because Ford cars are not the most user-friendly in that regard.

Spice Burger · 13-09-2015 8:04pm

Thank you both for your posts.
I did mention to the garage that I did'nt think the sensor was the issue but alas the sensor was changed & all oK on test drive so job done :-\
No noticeable issue on start up.Sometimes the car feels feels sluggish for a couple of seconds in 2nd gear then kicks back to life.
Need to get her checked / diagnosed properly as the sensor seems to be flagging another problem somewhere.
Thanks lads.Will post any future outcome :-)

martinr5232 · 13-09-2015 8:36pm

PukkaStukka wrote:

Cranks sensor can cause running as well as starting faults. The garage obviously saw a crank sensor fault code and that's what they plumped for it. Why would a faulty cluster cause a crank code?? If the cluster was causing the car to cut out then the cluster itself should generate its own code. That obviously depends too if the scan tool the garage used was a suitable one for reading those codes because Ford cars are not the most user-friendly in that regard.

I dont know what codes came up and i dont know what equipment was used neither do you.

As for a cluster creating a code maybe it did and the non genuine code reader interpreted it wrong it was quiet possibly a U code which is a communication fault but you need to know how to interpret what you are looking at and not just throw parts at it and hope it fixes it.

PukkaStukka · 13-09-2015 9:32pm

martinr5232 wrote: »

I dont know what codes came up and i dont know what equipment was used neither do you.

As for a cluster creating a code maybe it did and the non genuine code reader interpreted it wrong it was quiet possibly a U code which is a communication fault but you need to know how to interpret what you are looking at and not just throw parts at it and hope it fixes it.

Of course I don't know what equipment was used. But the fact that crank sensor codes consistently came up, and a replacement sensor worked initially suggest there was / is some validity to those codes.

If the garage has an oscilloscope, they could've scoped the output from the sensor before replacement to see what is being produced. That'll confirm if it is the sensor or something further upstream in the wiring or the PCM. I also mentioned if previous sensors were physically damaged. The link I posted above and other anecdotes I've heard suggest some Ford engines have form for this....

ted1 · 13-09-2015 9:34pm

The misses had a similar issue, turned out there was a tiny oil leak above it that kept covering the sensor

Spice Burger · 15-09-2015 5:50pm

A deeper diagnostics check was carried out on electric circuit .wiring / looms/instrument cluster etc.
No physical damage to sensor.Garage had the older one to show me & that had no signs of wear.Washer added as possible fix but made no difference.
Signal & data to Instrument cluster was found to be sound.Communication between sensor & ecu was also OK.
They checked the timing and all OK.
Looking like the computer could be the guilty party.

PukkaStukka · 16-09-2015 11:22pm

Ouch, that'll be expensive! If you opt to have it replaced but the fault persists thereafter, will the garage refund you the cost of the parts?? I doubt it....

Alternatively, if you can live without the car for a short while, you could have the PCM sent away for testing. Personally and if it were mine, I would consider this particular option before condemning and replacing the PCM.

Spice Burger · 17-09-2015 7:18pm

Gutted..I have had a hell of a lot of work done on the vehicle since purchase 3 years ago.

Replacing the pcm is not an option at the minute as I simply cannot afford.As you rightly say,I could get it replaced and all that goes with it, only to find the problem hasn't resolved itself : - o I think your original thoughts that clutch debris messing with the flywheel or the engine having excessive crankshaft float havn't been disproved.What's involved with diagnosis and repair here?

Funnily enough ,as expected yesterday the tach sprung back to life.Before setting off for home after work , I turned iginition key on and off a few times without starting the engine.Then turned engine on, drove about 200 metres & on an incline, hey presto working again.engine management light extinguished today& working fine.

I have been advised that if I donot plan on selling the vehicle before she hits the scrap heap, I should just learn to live with intermittent fault..

Crankshaft position sensor

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