VW Golf MK4 EMS Warning Dashlight.

golfbgud

EMS light on dashboard coming on - Reset twice.
Goes out for a few days and then comes back on.
Car is driving fine.
Code was related to Catalytic Converter.
1400CC Petrol with 110k miles.

Question:
(1) Anyone had a similar problem?
(2) Was it a cat replacement or sensor replacement?
(3) How much for both?
(4) Where to buy parts?
(5) New or Used?

Thanks in advance.

Tipsy Mac

Sure it's not an EPC warning light?

westcoastred

I have found that the electrics can be a bit dodgy on these golfs. Often, it just a sensor that has malfunctioned and if you've had it checked out and reset I would say that this is definately the problem. I saw the engine management light come on on the dash for a faulty rear light before!

Mr.Diagnostic

Sensors and cats can be tested to see if they are faulty. Fault codes are only a direction for a diagnosis not a diagnosis in themselves.


Testing will work out cheaper than guessing, unless you are very lucky!

golfbgud

I'm told the cat is gone. Mechanic tested the emmissions and it failed

"Measurement at Idle not OK".

LAMBDA 1.045

Seems to make sense if the code was pointing to cat and cat is failing emmissions under a separate test?

Anyone got any advice on whether to use new or 2ndhand and what the likely costs will be?

Appreciate the feedback.....Thanks.

promethius

Hey i replaced mine recently, cost about 220 euro all in to fit it, it was a generic one the garage recommended.

golfbgud

promethius wrote: »

Hey i replaced mine recently, cost about 220 euro all in to fit it, it was a generic one the garage recommended.

Thanks PROM.

You remember what the name of the generic part was? I see plenty of them on the web......Thanks.

golfbgud

Tipsy Mac wrote: »

Sure it's not an EPC warning light?

Deffo not the EPC light.

Its the one with the engine sign.......

Mr.Diagnostic

golfbgud wrote: »

I'm told the cat is gone. Mechanic tested the emmissions and it failed

"Measurement at Idle not OK".

LAMBDA 1.045

Are you saying the only problem was the lambda reading and only at idle?

If so, then that is not a faulty cat.

golfbgud

Now I'm getting anxious!

Attached is the printed report.....

Apprecaite your feedback Mr D.

Car is owned by my daughter. Only has it 2 weeks and is upset already!

Mr.Diagnostic

golfbgud wrote: »

Attached is the printed report.....

Based on those reading I would not be buying a cat.

There is a series of checks needed but the first thing i would look for would be dirty throttle body and a vac leak. That car has a breather flap built into the intake trunking which could cause similar.

I would be prepared to bet the fault code logged was for O2 sensor signal low??

golfbgud

I didn't get the actual failure codes (will try asking later) but there's a note on the back of the emmissions slip saying:

"cat + lambda sensor" ?

Light was reset twice in recent weeks and came back on showing same issue? That's why he checked the emmissions and said that the cat was gone?

R.O.R

Any chance it's one of the coils about to pack up?

I had an EML light on my Octavia (1.8T) for ages before the coils started to go. I'd reset the light by disconecting the battery, but it would always come back on in a couple of days.

Would an inefficient coil cause high emissions?

golfbgud

Borrowed a friends scanner tonight and it spat out the following:

Codes x9

1. 16804 Catalyst System, Bank1 Efficiency Below Threshold
2. 16645 Cylinder 1 Injector Circuit Low Input/Short to ground
3. 16651 Cylinder 3 Injector Circuit Low Input/Short to ground
4. 16654 Cylinder 4 Injector, Circuit Low Input / Short to ground
5. 16648 Cylinder 2 Injector, Circuit Low Input / Short to ground
6. 17833 Tank Ventilation Valve - Short to Ground
7. 17525 Oxygen (Lambda) Sensor Heating Circuit, Bank-1 Sensor-2, Short to Ground
8. 17953 Throttle Valve Controller, Malfunction
9. 18010 Power Supply (B+) Terminal 30 Low Voltage

Battery was disconnected recently to sort starter problem. Car is harder to start recently (hot or cold).

I have cleared the codes and may drive it to work tomorrow to see what codes come back...

Any hints/clues above anyone?

Thanks....

AzureAuto

Hi,
Problem is high CO at idle, i.e. 0.5% when max to pass emissions test is 0.3%. High CO indicates a rich mix at idle, yet at fast idle the emissions are within spec...
Rich mix= injectors increasing output of fuel due to oxygen sensor signal indicating an excess of oxygen in exhaust gases. Reason 1) vacuum leak from the engine, suggest using carb spray or Wd40 and spraying around all vacuum pipes, unions, rubber hoses with car running at idle, an increses in revs will show up a leak. Reason 2) Sluggish or faulty lambda sensor? Indeed it apears to be showing lambda switching to 1.045 which is 0.15 outside of the typical switching window (0.97-1.030).
Get your mechanic to test the switching of sensor using oscilloscope/graphing scanner. Any waveform indicating a voltage less than 200mv (0.2V) or in excess of 1000mv (1v) at idle should be considered knackered, which wouldnt suprise me for car with 118K on the clock!
Not dismissing the CAT but suggest to check the cheaper options first

golfbgud

Read the codes again tonight (after last reset) and got similar results to the last test:

16645
16651
16654
16648
17833
17525
16804

golfbgud

Hooked up a 409 Vers of VAGCOM to check codes and it spat out the following:

Borrowed a friends scanner tonight and it spat out the following:

Codes x 6

1. 16645 Cylinder 1 Injector Circuit Low Input/Short to ground
2. 16651 Cylinder 3 Injector Circuit Low Input/Short to ground
3. 16654 Cylinder 4 Injector, Circuit Low Input / Short to ground
4. 16648 Cylinder 2 Injector, Circuit Low Input / Short to ground
5. 17833 Tank Ventilation Valve - Short to Ground
6. 17525 Oxygen (Lambda) Sensor Heating Circuit, Bank-1 Sensor-2, Short to Ground

Mr.Diagnostic

You have a relay/power supply problem.

beachlife

The code relating to the o2 sensor is saying that the heater circuit is not

working,on some models this is fused,so worth checking the fuses
.
Also you can test the rear lambda sensor(02) This is the faulty sensor,

If this sensor is not working then it may well be causing the code for the

cat.
because the ecu can't get any feed back from the sensor to analyze the cat

As for the injector codes,short to ground circuit low,this could well be a relay issue/or a wiring problem. and usually is what it states. A short to ground(i.e a broken wire or shorted out component,relay etc)

I feel you car does not need a cat but has a few small wiring issues and needs someone to check the circuitry properly

golfbgud

OK Guys so we replaced the Relay 109 and the car is now starting properly so good call by you and thanks.

Car ran without light for two weeks and about 113 miles (all short trips around town).

Light came back on yesterday and only one code this time :



VAG-COM Version: Release 409.1-US
Chassis Type: 1J - VW G/J/B Mk4
Scan: 01,02,03,08,16,15,17,19,22,35,46,56

---

Address 01: Engine
Controller: 036 906 032 D
Component: ME7.5.10 3398
Coding: 00031
Shop #: WSC 00810

1 Fault Found:

16804 - Catalyst System: Bank 1: Efficiency Below Threshold
P0420 - 35-00 - -
Readiness: 0000 0000
________________________________________


Converter - Low Efficiency
16804 P0420 Catalyst System Bank-1, Efficiency Below Threshold

golfbgud

Looks like we're back on the emissions/cat track again......

I've read about stuff like trying cat cleaner, changing air filter etc but I'm open to more suggestions.

Does this point to the sensor before the cat?

I'm using the shareware version of VAGCOM - Would the full version tell me more about this problem? Trying to avoid more huge costs (Christmas is coming).

Thanks.

beachlife

Do you have live data? You need to see if the car is running right.that's the first thing. by right I mean is the car running rich or lean? or is there any leaks or restrictions in the exhausts. If the front sensor is okay. then you need to test the rear sensor. If the sensor is okay then yes it's the cat.
So to check:
1. check the reading of first sensor to ensure it is okay.

2. If sensors tests okay then what is the fueling like on the car(rich,lean,okay)

3. If running rich/lean Then whats the cause(air intake leak/air flow meter/injectors etc...)

4. once you have established that the fueling is okay then you can move on to check the rear 02 sensor.

5. check exhaust for holes leaks etc.

6. if all is fine up to this point then replace cat. job Done!! take car for a good spin and then get the emissions tested to confirm repair.