Car judders, rev fluctuation & battery light

[Albert27]

Hi guys,

Need some advice for a friend who's got a 2006 mk2 petrol 1.6 focus.

At motorway speeds the car is juddering, the rev counter fluctuates continuously, and during the judder the battery light comes on.  Check engine light has come on so i put forscan to it and got following codes:

P0335-E2 / CKP sensor circuit fault

P0335-C / CKP sensor circuit fault

U2196- 20 / Invalid Engine rpm data

U2200- 20/ Invalid data for odometer

U1900 - 60/ CAN Communication bus fault.

The crankshaft position sensor has been replaced & car fully serviced but still doing it.

Any thoughts on what to try next or any advice?

Cheers

[mjt]

I think the U1900 code is the significant factor. It sounds like the instrument cluster problem that Tdci-Peter has described a number of times.

[Tdci-Peter]

22 hours ago, Albert27 said:

P0335-E2 / CKP sensor circuit fault

P0335-C / CKP sensor circuit fault

U2196- 20 / Invalid Engine rpm data

U2200- 20/ Invalid data for odometer

U1900 - 60/ CAN Communication bus fault.

The crankshaft position sensor has been replaced & car fully serviced but still doing it.

I am not so sure of the U1900 error. It can happen as a result of connecting & setting up the diagnostic system. On its own it is not very significant, unless it keeps happening very often.

My top suspect is the wiring from the Crankshaft sensor to the PCM. Then probably the camshaft sensor. These two sensors are continuously compared, I think, and faults in one can be confused with faults in the other. I had Crankshaft sensor errors on my last Vauxhall, and ended up replacing both to cure the fault.

One missing bit of data is which module all the DTCs were in. If they were all in the PCM, then I think it has to be one of those sensors (a faulty replacement CKP is improbable but not impossible), or its wiring, or failing that, the pcm itself (unlikely!)

If some DTCs were in the IC, then maybe communications problems could be the cause. But the reported CKP circuit faults could well cause the invalid rpm & odometer data.

It might be worth trying to run the car with either one of the camshaft or crankshaft sensors disconnected. It should be able to run on either alone, in reduced power mode probably. A disconnected sensor can be better then a faulty one sometimes.

[Albert27]

3 hours ago, Tdci-Peter said:

I am not so sure of the U1900 error. It can happen as a result of connecting & setting up the diagnostic system. On its own it is not very significant, unless it keeps happening very often.

My top suspect is the wiring from the Crankshaft sensor to the PCM. Then probably the camshaft sensor. These two sensors are continuously compared, I think, and faults in one can be confused with faults in the other. I had Crankshaft sensor errors on my last Vauxhall, and ended up replacing both to cure the fault.

One missing bit of data is which module all the DTCs were in. If they were all in the PCM, then I think it has to be one of those sensors (a faulty replacement CKP is improbable but not impossible), or its wiring, or failing that, the pcm itself (unlikely!)

If some DTCs were in the IC, then maybe communications problems could be the cause. But the reported CKP circuit faults could well cause the invalid rpm & odometer data.

It might be worth trying to run the car with either one of the camshaft or crankshaft sensors disconnected. It should be able to run on either alone, in reduced power mode probably. A disconnected sensor can be better then a faulty one sometimes.

One CKP DTC was in the PCM section, the other P code was in OBDII Diagnostics (not sure what that is) and the other 3 U code's were in IC.

Thanks for the info Peter, as always so informative.  I learn so much from this forum.  A few questions spring to mind.

If it is the wiring, is there a DIY fix and how?  If not, what would my friend's garage likely do to rectify it, just replace the wiring?  If it is a fairly straightforward DIY task i may try and have a go to save him some cash, but if it's going to get messy, i'd rather just send him to the garage armed with the knowledge of likely causes as we live a fair distance away!

The crankshaft sensor has been replaced so i'm fairly sure we can discount that for now.  Where is the camshaft sensor and how do i get to it on a 2006 1.6 petrol?

 

[Tdci-Peter]

1 hour ago, Albert27 said:

One CKP DTC was in the PCM section, the other P code was in OBDII Diagnostics (not sure what that is) and the other 3 U code's were in IC.

I am 99% sure the OBDii module is a "virtual" module, that is created, probably inside the pcm, for full compatibility with the OBDii international standards, which is a legal requirement. It holds copies of the standard OBDii DTCs and other info, which standard OBD tools can access. The pcm itself, can have these standardised DTCs & PIDs, plus any amount of manufacturer specific stuff. When using a tool like Forscan, which can access almost all Ford stuff, it does not really matter, as far as I know.

I do not think it says anywhere if it is the Ti-VCT, or the standard non-VCT 1.6. It makes a difference, the VCT engine has two camshaft sensors (the camshafts are independently adjustable), the non-VCT engine only has one sensor. I can not find a picture of it in situ, they are usually relatively easy to get at, on the Ti-VCT the CMP (camshaft position sensor) connectors have to be removed before the camcover can be removed, so must be outside this cover.

If it is the Ti-VCT, I would suspect the CMPs less, as I suspect if one of these failed, the pcm would know, by comparing it to the other CMP, and flag up a different error.

Whether the wiring is easy to fix depends what is wrong. You may be lucky and a squirt of contact cleaner will get it working, at least for a while. Or it may need a section of wiring loom replaced. The connectors at the PCM end are usually protected by a tamper-proof cover, that needs a headless bolt to be drilled out.

Even with those 3 DTCs in the IC, I think engine sensor or sensor wiring problems are most likely. There would usually be a lot more data errors from other modules if there was a CANbus problem, like the classic 2006 Focus IC problem. So keep scanning if the car is being used or even just started, to see if anything else pops up.

[Tdci-Peter]

On 08/05/2017 at 7:13 PM, Albert27 said:

during the judder the battery light comes on.

I did notice this symptom before, but thought a side effect of the judder or badly known rpm.

However, to add to the mix, I know that dodgy alternators can give some strange effects. My neighbor had a van that would start & idle, but then utterly ignored the throttle. Until stopped & started again, then it worked. That had the battery light on, and the battery was going flat. It was a faulty alternator.

If there is an intermittent fault, possibly in one phase, then the alternator may be keeping the battery charged, but when warmed up, and at speed, it could be mucking up the system voltage (the "12v", which should be about 14v when running).

The CKP is probably quite sensitive to voltage problems, as it is sensing passing teeth at quite a high speed.

But I still think CKP wiring faults are more likely. With no alternator of battery DTCs, and no other effects, it is hard to blame the alternator. Also the PCM is inherently capable of operating with low or variable supply voltage, as it has to do this on a cold start.

But does the battery start the car with good cranking speed, or is it getting sluggish? Something else to look at I am afraid!

 

[Albert27]

 

1 hour ago, Tdci-Peter said:

That had the battery light on, and the battery was going flat. It was a faulty alternator.

 Thanks for that Peter.  I will have a good thorough read tomorrow and come back with any questions.  I got the reg today so will look it up when i get a minute and clarify the specific engine.  I have a multimeter so should be able to rule the alternator out.

[Albert27]

Just an update: Problem caused as you suggested @Tdci-Peter by a broken wire from the crankshaft sensor.  As ever, thanks for all the help!