Apologies if this is something I could have searched for, I really struggled to come up with good keywords.

 

I have a Skoda Fabia 2011 DSG petrol with a problem. I bought it a couple months ago and the previous owner had the car since new and sold it because it had this problem.

 

When the car starts, it runs great. Although once while driving, it switched into limp-home mode, so I turned it off then on again, and it was back to normal. When this happened, I scanned for error codes and there were so many, including a limp-home code, that I don't think they had ever been cleared and it was hard to tell whether any of them were relevant to this incident. So I cleared them and waited. I'm not so concerned about this problem as it's happened only once, but I've written it here for completeness.

 

The more common problem, having happened now 4 times during my ownership, is that the car will not start for a day or two at a time. Turning the key all the way engages the starter motor which can be heard turning the engine but the engine does not fire. The car will refuse to start for a seemingly random amount of time, perhaps a day or two, then it will start first time every time again. No error codes are triggered when this happens, except for code 00821 which seems to always be there about the radio's second antenna.

 

I read somewhere that turning the key to the on position engages the fuel pump for priming, and indeed I can hear something whirring for a few seconds each time I turn the key to this position. I tried turning the key on and off 5-10 times and only then turning the key all the way to engage the starter motor. This causes the engine to fire, but only for a few turns.

 

This indicates to me that the plugs are sparking and that the fuel pump is working. I could be wrong, of course. So what could it be? And how big of a job is it to replace?

Hello, welcome to the forum. This sounds to me as if it might be an intermittent problem with the immobiliser. Have you tried using the second key (if you have one) when this problem occurs?  

7 minutes ago, Warrior193 said:

Have you tried using the second key (if you have one) when this problem occurs?  

I haven't! But I do have a second key and this is an easy one to test, thanks for the suggestion. The intermittent nature of the problem means I might not be able to do so for a little while, but I promise to update this thread whenever that may be.

Looking more closely at the two keys, the key that I've deemed the spare key appears to be more worn. So I think the previous owner was using this one as their main one. Knowing that the previous owner was already experiencing this problem I don't think the key is the problem.

 

In any case, I'll still try the swap next time the problem presents, as it's worth a shot.

On the contrary, unless I have misunderstood what you wrote it suggests to me that the problem is definitely the RFID chip of the key you are using not being recognised.

 

It could be that the other key is even worse and will never start the vehicle, that does not mean its another fault, I believe the RFID coil around the ignition switch is misplaced or has a weak field, the original worn key would have become problematic, the spare behaving better, as always these problems get worse over time.

I would be looking towards cam/crank position sensor rather than an immob issue a good way of figuring this out would be with vcds live data checking if fueling or not on while cranking 

Opening the drivers door primes the fuel when the car has been sat an hour or 3 or longer.

 

http://briskoda.net/forums/topic/217514-motor-noise-upon-opening-drivers-door-but-not-the-other-doors

 

 

Edited 18 August, 20232 yr by toot

21 hours ago, thomasaspin said:

I would be looking towards cam/crank position sensor rather than an immob issue a good way of figuring this out would be with vcds live data checking if fueling or not on while cranking 

Unfortunately I don't have VCDS, but I do have a Vgate iCar Pro (bluetooth) and Car Scanner (Android). Here are the codes from today:

 

Car Scanner ELM OBD2
Version: 1.99.5/400995/GP
DTC report
Connection profile: Skoda OBD-II / EOBD 1.0L-2.0L TSI/TFSI CAN-UDS + AT/DSG (PQ26, MQB, MLB, MSB, etc.)Date: 18/08/2023 12:28:55
VIN: 
============================
OBD-II
No DTC found.
============================
19. CAN Gateway
No DTC found.
============================
09. Onboard supply control unit
No DTC found.
============================
01. Engine control unit01. Engine control unit
DTCs: 1
----------------------------
11003 [0x002AFB] Archive (inactive)
P044100: EVAP Emission Contr.Sys.Incorrect, Purge Flow
EVAP Emission Contr.Sys.Incorrect Purge Flow
P044100: EVAP Emission Contr.Sys.Incorrect, Purge Flow
Status: Test failed since last DTC clear, Test not completed during this operation cycle
============================
08. Heater and climate
No DTC found.
============================
10. Parking Assistant 2
No DTC found.
============================
15. SRS
No DTC found.
============================
17. Dashboard
No DTC found.
============================
25. Immobilizer
No DTC found.
============================
56. Head unit (MMI) (VW TP2.0)56. Head unit (MMI) (VW TP2.0)
DTCs: 1
----------------------------
00821 [0x0335]
Antenna 2 radio-R93; Antenna 2 for radio R93; Engine speed sender-G28 malfunction
Status: Pending fault present, Pending fault present during this driving cycle, Test is inhibited by other DTC, Validated and stored in non volatile memory, Validated fault present at time of request
============================
76. Parking assistant
No DTC found.

 

I noticed these things:

1. 11003 is new... but a quick search leads me to believe that this shouldn't prevent the engine from firing

2. 00821 could be about the radio's antenna (like I wrote in the OP), but could also be about the engine speed sender (sensor?), just like @thomasaspin suggests. I feel a bit silly for missing that, that's almost certainly it, right?

 

If so, is this a big job to replace? Please guide me towards the right part to order and roughly where it is under the bonnet.

Edited 19 August, 20232 yr by ColinD

If it is the immobiliser sensor coil, I cured that on my Volvo S40 by moving the steering wheel position (while checking to see how easy it was to remove the cowl) and after that I never had any issues (possible poor connection or it moved slightly). However, when I tried to start the car with the fault it wouldn't turn over, just the immobiliser light flashing.

It's under the car rather than under the bonnet!

1 minute ago, sepulchrave said:

It's under the car rather than under the bonnet!

Can you provide any more info? It's a CBZB engine. I'm currently scouring the net for details of the sensor's location, there has to be something somewhere, it's just not proving easy to find.

So far I've collected this information:

 

Quote

Engine speed sender -G28-
- at rear crankshaft sealing flange, suction side

https://workshop-manuals.com/skoda/fabia-mk2/power_unit/1.6/77_kw_mpi_engine/mixture_preparation_system_electronic_inj.gas/fuel_injection_system/injection_and_ignition_system_overview_of_fitting_locations/

 

Quote

The engine speed sender -G28- is integrated in the sealing flange on the flywheel side.

Special tools and workshop equipment required
- Socket insert 4 mm -T10370-
- Assembly device -T10118-
Removing
- Remove the noise insulation.
- Disconnect the plug -arrow- for the engine speed sender -G28- using the assembly device -T10118-.
Note: To disconnect the plug without using the assembly device -T10118-, carefully lever off the plug with a suitable screwdriver and at the same time lift up the release button with a thin wire hook.
- Release the fixing screw -arrow- and pull out the engine speed sender -G28-.

https://workshop-manuals.com/skoda/fabia-mk2/power_unit/1.6/77_kw_mpi_engine/mixture_preparation_system_electronic_inj.gas/fuel_injection_system/removing_and_installing_engine_speed_senderg28/

 

Where is that 7 arrow even pointing?

I can't see anything that resembles the second two sketches, probably because it's behind some noise insulation. Again, where's that?

It'll be on the opposite side from the starter motor, you'll need to get under the car to stand any chance of seeing it.

The sensor is right at the bottom of the block near where the gearbox is if memory serves , it is possible to do with a deep socket I’m sure it screws into the block , it’s worth getting it on a ramp if possible or on two jacks and checking it out 

The car has started failing more frequently. It will more often not start and and stop itself while driving. This is a good thing: hopefully a mechanic can witness the problem and solve it more confidently.

 

I've taken it to the garage to let an expert deal with it. I'll update this thread once I know more.

1 hour ago, rcambrj said:

The car has started failing more frequently. It will more often not start and and stop itself while driving. This is a good thing: hopefully a mechanic can witness the problem and solve it more confidently.

 

I've taken it to the garage to let an expert deal with it. I'll update this thread once I know more.

 

I don't blame you for getting the garage to do it, you really do need a proper car lift and good lighting to tackle the crank sensor, even then it basically has to be done blind.

The car is back with a new battery (old one may have been dead due to using the starter motor so much), a new fuel pump relay and a new ignition coil. I hope that's the end of it.

Sounds like the mechanic has thrown the kitchen sink at it , why didn’t he do the crank sensor like was agreed ? 

He probably did on the qiuet after all the parts the OP had to stump up for made no difference.

 

I bought the crank sensor myself and took it to the mechanic along with the DTCs printed on a piece of paper, he didn't think that a new crank sensor would solve the problem. I still have the unused crank sensor.

 

The mechanic had called me to tell me the car was ready. The battery and fuel pump relay had already been replaced. I was sent a video of the battery problem (starter motor would not turn), like I say it might have just been discharged through starter motor overuse, but batteries being consumables I'm fine with this.

 

The fuel pump relay is a weird one I don't quite understand, but it was a second hand one so negligible cost.

 

When I got there, the mechanic asked me to test the car, and it was still consistently stopping. Quite strange that he didn't test it himself, but to his credit, he started work on it straightaway.

 

He removed the fuel line and turned the key on, at which point fuel could be seen coming out. Fuel pump (and relay) good. He removed a spark plug cable and checked for current while the starter motor was turning, nothing. He unplugged the coil and plugged it back in, car started up.

 

The car made the 30 minute drive home, which is more than it could do just before it went into the garage. But I'm still skeptical as the problem might have just subsided back to what it was before: something that happens every few weeks. If the problem persists I guess I'll be continuing the conversation with him, along with some awkward questions about the parts I've paid for.

 

Even though I'm delegating this to the mechanic, I very much appreciate all your comments. Please keep them coming and I'll do my part to keep this thread up to date too. I hope it will be useful to someone.

The coils not firing is a typical sign of a crank position sensor problem it’s literally in the fault code I can’t believe a mechanic would be so careless as to not replace it , the crank position sensor tells the ecu when to fire the coils and inject fuel so without that working correctly the ecu will do neither throwing the parts bin at it suggests to me a mechanic who doesn’t know there trade 

How many these days are within their sphere of competence with modern vehicle electronics?

 

That is not running them down as even a poor Motor Mechanic of today has probably had more education and training than his counterpart of previous generations most of whom would not really have understood the Kettering ignition system but the level of complexity of the vehicle electronics and emissions systems  is way out of whack with the educational entry requirements for the trade.

Fuel pump relay used to be a common problem in VAG models. Dry joints in the relay.

Guys, the car's fixed, the OP is happy, it wasn't the crank sensor, all's well that ends well.

3 hours ago, sepulchrave said:

the car's fixed

It's too soon to say, but I sure hope so!

 

I do see that it could still be the crank sensor though, like @thomasaspin says. Like I say, I'll keep you all informed 😋

Edited 2 September, 20232 yr by rcambrj