Motor control system failure - rpm sender issue? - Alfa Romeo Forum
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Motor control system failure - rpm sender issue?

Hi,
Just one week into ownership and 1st issue...
Yesterday, I drove my car for a bit with no problems. When I got to drive it again a bit later on, once I turned the engine on it showed a motor Control system failure warning on the dash. I took the car to an Alfa specialist and they told me it was an rpm sender error. They cleared the fault and off I went without any warnings on the dash.
Today I went on a mid distance journey without an issue and when starting the engine to set off to go back home, it again showed the mcsf warning on the dash. I decided to drive the car anyway and to be honest, the car did not feel running rough or anything (although I was careful not to drive it too fast)
The thing is I know that the previous owner had replaced the rpm sender about 3 months ago so I don't think is a case of replacing the sensor.
Does anyone have any ideas of what could it be?
Many thanks

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Last edited by TheVarix; 10-07-16 at 17:00.
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You should get the error code read out to see if the ECU still indicates RPM sensor (crank sensor)
If it still does I would a connection problem to the sensor or the sensor hasn't been fitted properly.
Do you if the RPM sensor was a Bosch or from another vendor?

You are luckey that you don't have sudden have an engine cut-out andit won't start again until cooled down, which is the typical error when you have crank sensor problems
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Originally Posted by Henrik_45 View Post
You should get the error code read out to see if the ECU still indicates RPM sensor (crank sensor)
If it still does I would a connection problem to the sensor or the sensor hasn't been fitted properly.
Do you if the RPM sensor was a Bosch or from another vendor?

You are luckey that you don't have sudden have an engine cut-out andit won't start again until cooled down, which is the typical error when you have crank sensor problems
Thanks for the reply. No, I don't know what they replaced it with Bosch or other. All I know it's the part was £60 without vat, if that gives you a clue... It was replaced by an Alfa specialist but we'll, I guess even the specialists can make mistakes...
I am afraid though that I don't know where to look for it. I have read it's at the back of the engine. Is it possible to check from the top of do I need to check it from below? I have had a look online at pics of the sensor to know what to look for but any pic. Or description of where the sensor is would be quite helpful actually...
Do you recommend not to drive the car then?


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Just because the dealer charged £60 for it doesn't mean its a £60 part..

This price implies cheap part marked up ..

Bosch or nothing with these cars..
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Thanks. I agree with you. I'll have it rediagnosed and if a replacement is needed, I'll request with the Bosch sensor. I would have a look down there but we have guests this afternoon so it won't be possible for me to check... Do you think it's safe to drive the car? Could it be an intermittent problem?
By the way, is there any good error reader with which to clear errors as well. I had a nice hand held one for my TT I bought on eBay and it was really handy. I have seen on ebay for £15 one eobd / obd2 reader that can read and clear errors and the Mil light. Is that OK for a Alfa 156 55 reg?

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I use torque app pro on my samsung S6 with an elm 327 bluetooth interface.

Reads and clears all codes except airbags.

CPS is under the starter motor..
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I intend to have a look today (weather permitting) at the rpm sender to see if it's fitted properly. Anything to look for? Is there any danger in spraying and cleaning with electrical contact cleaner spray?

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Won't harm it but its just a simple hall effect sensor so if its faulty its faulty!

Keep us posted..:-)
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Well, as yesterday's weather was a bit crap, I decided not to have a look the sensor. The funny thing is that yesterday I parked the car outside of the house after work, realised it's a bit far off the kerb. Started the engine again and to my surprise the mcsf warning light is gone! Been driving today as well without any warning at all... This has left me a bit puzzled to say the least. Well, I'll make a sacrificial offering of pink coolant to the gods of motoring to see if the warning light doesn't come back, although I must admit I'm not too hopeful...

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MCSF will go away after a few re-starts if there was a transient non-fatal fault. That's normal behaviour. You should still look at logged codes to see what caused the problem in the first place.
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Well. I knew the motoring gods would ignore me... The mcsf light has come back. I've scanned the car and the error thrown (twice) was:
P0335 crankshaft position sensor A circuit.
Any ideas of what could be the fault? I guess the most obvious are a faulty sensor, loose connection and/or wiring to ecu. Any ideas of how to diagnose?
The sensor has been replaced very recently by an Alfa Specialist so this problem has reocurred. I don't want to spend £72 (Local Alfa dealer prices) if that's not the problem...Could it be possible that it's a faulty Ecu? If that's the case I might consider rejecting the car. I don't want to spend hundreds of pounds diagnosing something that then it's also going to cost me hundreds more to repair...

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Reject it just on principal really..can't believe how many dealers are selling cars with faults!

When you buy a used car work on the assumption thaf it "should" in theory be prepared to a standard where you shouldn't have any issues for one service interval or 6 months ,whichever is sooner,orif sold with fault price should reflect that.

A recurring MCSF light with a fault that has been known and new part failed to resolve would worry me TBH.

Give them a choice

Fix it permanently or take the car back.
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Hi,
Thanks for the reply but I have a bit of a problem as the dealer is more than 150 miles from me! So a quick visit is out of the question. I've spoken to him today and I agreed with him that I would take the car to my local Alfa specialist to have a proper diagnosis and then we would take it from there. Depending what the diagnostic is, I'll ask him to either give me a partial refund covering whatever the repairs cost or a full refund if it turns out to be something serious (I want to give him the benefit of the doubt) He seemed to be willing to reach an amicable solution so let's see... The thing is, for the price I paid (£1850 after some haggling) there are not many cars in good condition and not too crazy miles. I had seen so many rubbish cars for about the same price before this one that I don't know, maybe I got a bit carried away... We'll see how all this ends but I'd be gutted to get rid of the car as it goes really well, the engine looks and sounds healthy and both the interior and exterior are in great condition (only 66k miles).

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Well, to me it doesn't sound like a big problem, just that the new CPS you had fitted has probably failed (just a duff one, or a crappy aftermarket non-Bosch substitute, or a loom/connection issue). That's easily and cheaply fixable, a minor glitch that could and often does happen with any car made since the mid-80s. You should ask the repairer to look for possible causes of this early failure including checking the flywheel ring gear for damage. (The CPS detects crank position from the ring gear - and damaged teeth can confuse it). That would require the gearbox to come out to repair, and might justify returning the car. But chances are it's just a duff CPS or connection, which is scarcely more reason to panic than a blown headlight bulb.
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Well, to me it doesn't sound like a big problem, just that the new CPS you had fitted has probably failed (just a duff one, or a crappy aftermarket non-Bosch substitute, or a loom/connection issue). That's easily and cheaply fixable, a minor glitch that could and often does happen with any car made since the mid-80s. You should ask the repairer to look for possible causes of this early failure including checking the flywheel ring gear for damage. (The CPS detects crank position from the ring gear - and damaged teeth can confuse it). That would require the gearbox to come out to repair, and might justify returning the car. But chances are it's just a duff CPS or connection, which is scarcely more reason to panic than a blown headlight bulb.
I have been told by the Alfa/Fiat specialist that looked after the previous owner that my car's cps doesn't read from the flywheel. I am really confused now...could he be mixing up camshaft and crankshaft sensors? I thought all ckp sensors read from the flywheel's ring gear... He told me that after replacing the sensor the problem reocurred so he told me that his 2 possible diagnostics were either wiring loom fault or ecu fault and told me that the previous owner decided not to investigate more.
If you see his previous bills he had had some expensive bills for a new radiator, and wishbones not too long before the sensor was replaced so maybe he got fed up! (although I know those are common things that go bad in these cars)
On the other hand I asked over the phone the guys at Gonella Brothers near me and mentioned what the other garage told me. They said to me that they had yet to come across a faulty Ecu on the jtd's. He suggested a problem on the flywheel side could be a possibility but that from his experience he doubted so.
Luckily the dealer has been really nice and offered a full refund if I so wish. I don't know, I really like the car and I might get it properly diagnosed. If it turns out to be something simple I guess I can also ask the dealer to cough up the cost of the repair (obviously before I pay anything). It's just that engine wise goes so well! I actually fell in love with the car. Ah....decisions, decisions....

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Well, I decided to resuscitate my own thread as the problem got solved in the end.
I contacted the garage (Alfa / Fiat specialist) the previous owner used to take the car to and they told me that they thought it was a wiring loom problem or maybe a faulty ECU!?!?
Thankfully I ignored their opinion and took the car to another garage (Firela motors, by the way) and they told me that they had yet to come across problems with the JTD's ECU or wiring loom like the ones I was having and they recommended to replace the rpm sender again as although it was nearly new, it could be faulty.
So I went to my local Alfa dealer and bought an OEM RPM Sensor. They fitted it for me and... problem solved! 3 months on and no more MCSF lights or errors thrown (fingers crossed!)
I checked the old rpm sensor and it was certainly different to the one I bought: the OLD one had a thin metal rod visible in the middle of the sensor while the OEM I bought at the dealers' did not have it. It seems that these cars don't like non OEM parts... Well although my symptoms were uncommon, I hope this helps someone in the future with the same or similar symptoms.
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