Ford Focus - Validity of driveway diagnosis vs dealer? | Technical matters | Back Room Forum

Thu 11 Feb 2016 11:59

Ford Focus - Validity of driveway diagnosis vs dealer? - Tesserat

I have a Ford Focus. End of last year it developed a yellow engine warning light situation and a sporadic misfire. I got it serviced by Ford and they told me it needed a new ignition coil. I thought this strange as I would have thought that an ignition coil problem would have resulted in a more continuous misfire. They replace the coil (and plugs, but NOT LEADS). Now, less than two months later, it has developed a very serious misfire (any cylinder I think, but not sure). There is now a RED warning light that apparently means (Message Center (urgent)). I suspected it might be the coil again, so I called in local driveway diagnostics man who discovered that it indeed is (or appears to be - error code P2303) - which would be covered by warranty.

So I immediately phoned the Ford dealer who told me that that I would have to deliver to them and that they would carry out their own diagnosis ("our meters can sometimes read more into the fault than others' can") and that if it was not the power pack at fault then I would be faced with a bill of £85 for the diagnosis and whatever it costs to fix the fault, Well I feel myself on the horns of a dilemma: this gives them any amount of leeway to tell me that it is not the coil but something else: £££bill for me and no comeback on themselves. Thing is: EOBD code readers are just reading fault codes from the ECU and transponding them into readable format, no? So how come Ford's meters can read more deeply that the ones that mobile mechanics use, and if Ford's diagnostic tools really are more intensive than proprietary ones (this is a Sealey), then why on earth didn't they find the underlying fault in December?

Edited by Tesserat on 11/02/2016 at 12:01

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Thu 11 Feb 2016 13:12

Ford Focus - Validity of driveway diagnosis vs dealer? - RobJP

Firstly, as you probably know : Yellow fault light is advisory. RED fault light = DO NOT USE.

You are assuming that the original fault and the new one are the same fault.

As the initial fault was only an advisory (yellow) fault, and this one is red (urgent) then it's entirely possible that it's two different faults.

Quite simply, get it into the Ford dealer if it's still under warranty. When they then diagnose the fault, if it is NOT covered by the warranty for whatever reason, you are not obliged to get any repair work carried out by them, you can get it done elsewhere.

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Thu 11 Feb 2016 14:41

Ford Focus - Validity of driveway diagnosis vs dealer? - Tesserat

Thanks Kindly.

As you will see from the title of the post "Validity of driveway diagnosis vs dealer?" and my summing-up in the last paragraph of OP, I am not playing a blame-game here: whatever the fault is, I need it fixing, of course. What I was getting at was (1) is a roadside diagnosis really reliable? If not - why not? If an ECU is not able to report on the primary cause of a problem, but only a symptom, then what is the point in that? I already knew I had a misfire and a red warning light ferchrissakes! For a diog to tell me that the fault is the coil pack (but not really) is not much help, is it? (2) are dealers' diagnostics really better than independent garages, when AFAIAA they are only reading the error codes that the ECU generates?

I'm not really asking you lot for solutions to my problem - just querying the point of electronic diagnoses.

Thanks.

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Thu 11 Feb 2016 15:36

Ford Focus - Validity of driveway diagnosis vs dealer? - RobJP

Some of the diagnostic tools are very good (and, generally, very expensive). Some do a lot less, and cost a lot less.

But a lot of it is in reading and understanding the fault codes. Any idiot can plug in a diagnostic tool and read fault codes, but the real skill is in being able to isolate and fix a problem from them.

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Thu 11 Feb 2016 16:10

Ford Focus - Validity of driveway diagnosis vs dealer? - Tesserat

Thanks AGAIN!

You have confirmed my suspicions, that the error code on the hand-held does not necessarily indicate a coil fault, per se, but the fact that the coil is not operating correctly. This could be due to a wiring defect in the loom (which seems very expensive = £500). (BTW I have checked plugs and multimetered the leads - no probs downstream). I do not know how to test the coil independently of the rest of the system. If not the coil, then it is gonna be the wiring to it. Well, that is not really the point of my post, but to find out whether driveway diagnosis can be relied upon...

Thks

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Thu 11 Feb 2016 17:25

Ford Focus - Validity of driveway diagnosis vs dealer? - elekie&a/c doctor

What age is this car?There is a known issue with some Focus models where the connector to the coil becomes a poor contact and can cause misfire issues.

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Thu 11 Feb 2016 18:08

Ford Focus - Validity of driveway diagnosis vs dealer? - Tesserat

2006. Yeah, I noticed on t'internet that the LT side might be the prob. Well, if it is, I just need to man up and pay up. But my initial problem is: ?do roadside diagnostics have any substantial meaning?; and how do I fare if I go to a dealer and he says " don't care what that mechanic says, our machine says you need a new loom (by the way, you can't see the printout")? Seems like on-board diagnosis makes one more of a hostage to fortune than ever!

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Thu 11 Feb 2016 18:51

Ford Focus - Validity of driveway diagnosis vs dealer? - elekie&a/c doctor

More to the point "Do any diagnostics have any substantial meaning"?Roadside or Main dealer doesn't matter,it all depends on the equipt being used and the experience of the operator.No diagnostic machine can say you need a new loom.Remember,computers are clever but they have no brain!Btw,the part you need cannot be bought from Ford,but is available on flea-bay here.

www.ebay.co.uk/itm/172039774306?_trksid=p2055119.m...T

Interestingly,the part has "Ford " stamped on it.Perhaps you now know something that the Main dealer doesn't.

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Fri 12 Feb 2016 15:58

Ford Focus - Validity of driveway diagnosis vs dealer? - Tesserat

That's what I need. Thanks for poting that link!

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Fri 12 Feb 2016 11:57

Ford Focus - Validity of driveway diagnosis vs dealer? - FoxyJukebox

A few years ago I had a fuel pump fault-causing misfires. I took it to the garage asking them to diagnose misfires-and their diagnostics came up with error codes ,which to put simply, did not reveal the fuel pump fault but only engine management symptoms.

I would investigate fuel pump failure

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Fri 12 Feb 2016 12:10

Ford Focus - Validity of driveway diagnosis vs dealer? - Tesserat

Gottit (I think). I had a look this morning, and there is a loose (I mean 'unattached') wire (orange & black to port #1) on the connector to the LT side of the coil pack. I suppose this was damaged when they replaced the previous coil two months ago. Whether the dealer will accept that is another matter, and whether the connector can be repaired without replacing the whole loom needs looking into...

Thanks all.

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Fri 12 Feb 2016 13:31

Ford Focus - Validity of driveway diagnosis vs dealer? - Railroad.

Sounds like you've fixed your problem so well done. The component is actually two coils in one pack. One coil fires cylinders 1 & 4, and the other fires cylinders 2 & 3. The centre terminal on the LT connector plug is a common 12v supply to both coils, and the outer two terminals are the negative returns which are switched by the ECM. Your poor connection would've meant the engine was only running on two cylinders.

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Fri 12 Feb 2016 14:08

Ford Focus - Validity of driveway diagnosis vs dealer? - Gibbo_Wirral

Thing is: EOBD code readers are just reading fault codes from the ECU and transponding them into readable format, no?

No, not always. Generic code readers don't pick up all faults, or cannot display live data or check components.

I've done some tests with various scanners on my car with a known EGR, diesel heater sensor, and glow plug faults and only the Peugeot specific diasgnostic gear picked up these fault codes and read the live data to show that the parts were indeed faulty.

And on two occasions I've known a national breakdown firm say that a customer's high pressure fuel pump has failed because that's what the code said, only for it to be an issue with the tank lift pump - one was a blocked filter in the pump, the other was weak current to the pump due to an old battery.

Don't get me wrong, reading codes yourself isn't bad, but you do need the skills and experience to be able to interpret the codes. Sometimes you can strike lucky, sometimes not. Depends if you like throwing money and parts at a problem.

And on the forum I frequent, I've lost count of the number of times a new member has registered because their car has a fault, they've had a driveway diagnostic only to be given the results "P1351 - Dealer specific code".

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Fri 12 Feb 2016 15:02

Ford Focus - Validity of driveway diagnosis vs dealer? - elekie&a/c doctor

As in my previous post,you can buy a coil connector repair kit from flea-bay for around £20.Ford dealer can only replace the whole loom.

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