Hi all,

I was driving home earlier today and the 'check engine' light (orange engine shaped light on the left side of the speedometer) came on out of the blue.

There are no strange sounds coming from the engine, the engine idles smoothly, the engine pulls fine through all gears, there is no "lumpiness" and no misfires throughout the entire rev range.

I have checked all fluids and all seem fine, I have checked all hoses and plugs as much as I could at the side of the road (just visual checks for obvious splits or loose hoses/disconnected plugs etc) and there don't appear to be any obvious issues.

I have tried various methods which are supposed to clear lights/errors (I don't know how many [if any] of these are genuine methods but I tried these regardless):

- Pressing in trip button for 2 seconds and turning to the right

- Pressing in trip button for 2 seconds with key turned to lights position, and turning to the right

- Pressing in trip button, holding, turning ignition to lights position, holding, turning ignition off, removing keys, and releasing button

I have also tried to reset the ECU using these two methods (Again, unsure if either of these are genuine methods, but I tried them regardless):

- Disconnecting negative terminal for 15 minutes and re-connecting, then starting engine

- Disconnecting negative terminal for 3 minutes, then re-connecting, then turning ignition to lights position, waiting 3 minutes, turning ignition off, removing key, putting key back in, then starting engine

Points to note:

- Engine had a full tank of petrol when this happened, it was cheap supermarket petrol though (Tesco 95) and I usually use Momentum/Ultimate/Super or sometimes Esso 95

- Radiator fan is faulty and non-working (blows fuses) but it has been like this for 2 weeks/500 miles, I have been careful with the engine, and never seen it go above 90 degrees. (replacement fan is in the post)

- The car was involved in an accident a few weeks ago, but it has been fine from after the repairs up until now (again, 2 weeks/500 miles) and it was fine before (never had the light come on)

The following parts were replaced:

- Front bumper

- Front offside wing & arch liner

- Lower front offside wishbone

- Front exhaust

- Radiator

- Front offside headlight cluster

The sump pan is dented, but not ruptured at all, and the inner wing was welded.

If anyone could shed any light on the subject or give me things to try, it would be much appreciated!

I do not have access to any diagnostic equipment, but I will be phoning my mechanic ASAP to get him to have a look at the fault codes and give the car a general once over to see what is wrong.

Finally, would you advise against driving the car while the check engine light is on persistently, even if there are no obvious issues?

Kind regards!

Edited 26 October, 201411 yr by acme15

The only way to clear the light is with diagnostic reader, it's a myth that disconnecting the battery will clear it, so without any fault codes it's impossible to say why the light has come on.

If it's running OK then your not going to do any harm running it while you wait for the codes to be read. By the year of the car a generic code reader will be able to read the codes so you could get one from Halfords or other motor factors

I haven't got the codes yet, but I took a closer look in the engine bay and traced the wires for the lambda sensors, and one of them looks like it has been chopped, re-soldered and taped up in the past, and further down the same wire, it looks like the wire got pinched in the accident and the insulation is ripped and there is bare wire showing.

Which of the many eBay code readers would you recommend?

My mechanic wants £20 to read the codes, but for £20 I could buy a generic code reader, do it myself, and then still have the reader.

If you have a laptop then I'd opt for a VCDS/Vagcom canbus lead and download (free) VCDS lite from the Ross Tech site, it'll definitely work on any VW and other makes that are obdll compatable

I don't have a laptop at the moment.

I sold it the day before this happened!

Where does the cable plug into in the car?

Edited 28 October, 201411 yr by acme15

ebay item 150541025281 it plugs in under the dash below the light switch

Thanks, I have ordered one with upgraded delivery, so it should arrive tomorrow.

Right so, the OBD reader returned three fault codes:

16804

17978

16556

The first one, 16804 isn't in the accompanying booklet, but Google suggests that it is "Catalyst System; Bank 1: Efficiency Below Threshold"

The second one, 17978 isn't in the accompanying booklet, but Google suggests that it is "Engine Start Blocked By Immobiliser"

The third one, 16556 is in the accompanying booklet, and it is "Fuel Trim: System Too Rich: Bank 1"

I am not concerned about the second one regarding the immobiliser, as the engine starts and runs fine, there have been no issues with the immobiliser, and I think it may have happened when I had a third party key programmed for the car.

So looking at the first and third ones then:

16804 - Catalyst System; Bank 1: Efficiency Below Threshold

16556 - Fuel Trim: System Too Rich: Bank 1

Any ideas?

Should I clear them and see if they come back, first off?

Thanks!

Edited 29 October, 201411 yr by acme15

Yes clear them, run it for a few days and then see if they return, although it's not faulting a lambda probe, both of those codes are common to one of the sensors giving out of normal range voltages

Cleared the codes and drove about 20 miles, cycled the ignition 5 or 6 times, no engine light yet.

I assume you've repaired your lambda wiring too?

PoloD.

That rather depends what you class as repaired. If you class winding loads of insulation tape around the damaged parts and cable tying it so that it doesnt flap about then yes. If you mean cutting out the damaged section, soldering the cable and heat-shrinking it, or replacing the cable, then no.

Edited 30 October, 201411 yr by acme15

Car was working fine for days and now won't start. Key turns to the lights position and they all come on and go out as normal, then the final turn which should trigger the starter does nothing.

Have tried both keys (original one included) one error is back, the fuel trim one.

Help?!

Edited 1 November, 201411 yr by acme15

Is it trying to turn over but not starting ? or is there nothing from the starter motor?

Hi mate, I sorted it a few minutes after I posted that. The cable had snapped off of the plug on the starter motor. No idea how that happened between 3PM and 7PM with a short town journey in the middle!

Fixed with a spade connector and a cable tie...

Should I worry about the "16556 - Fuel Trim: System Too Rich: Bank 1" error returning so soon? No check engine light though.

Edited 2 November, 201411 yr by acme15