I've an 02 plate polo, AWY Engine 1.2. 90K on the clock.

The last time i had a problem you kindly helped steer me in the right direction, i hope you can again.

 

My EPC Light came on last week, i cleaned the throttle body with carb cleaner and the light went out.

I then plugged in a cheap handheld code reader (Gendan) and found four codes, as follows .....

 

DTC03

16556 - Fuel trim bank 1 system too rich

 

16955 - Brake switch fault

 

16687 - Cylinder 3 misfire detected

 

DTC 01

01314 - Engine control module; No communication  or  Engine control module; Check DTC memory

 

After reading the codes the Epc light went out and has not come back on.

I have since changed the Spark plugs, the ones i removed were all in perfect condition (sandy coloured, no fouling) paying extra attention to cylinder 3 which was normal.

The car had a new Fuel Pump and Filter fitted 4,500 miles ago. It has only been used for relativley short journeys since then.

The car is using more fuel than normal and i can smell it running rich.

It starts first time, everytime and idles as normal.

The car seems to be running fine apart from the excessive fuel usage.

 

The brake switch above the pedal was changed by myself some time ago and the brake lights are working fine.The original Brake switch error codes had gone from the first time, so i cant understand why it should show again ?

The Coil packs are not due to go again just yet, i have changed them twice on this car due to them failing.

I have looked and looked for a Vac leak but cant see any at all.

 

Having plugged it in again with the Gendan, the Ecu code has gone, the other three still remain.

I understand it could be due to some common faults that this engine has e.g. Sticky exhaust valves, stretched chain etc but before i succumb to a garage i was wondering if any of you kind people could offer any assistance.

 

Thank you.

Short journeys = sooty lambda and cat.

 

Take the car for a good long motorway blast to cook it up and clear it out.

I'd have said o2 sensor maybe?

the misfire could be due to a bad coil do a power balance test by unplugging each coil one by one, note engine lower in power. pay attention to cylinder 3 .... Do you know how to do a coil test/ spark test... take out the coil and connect a spark tester. turn ignition. look for spark, or use a screw driver.  the fuel trim being rich may be due to a blocked air filter.... if not that simple try looking at the fuel pressure regulator on the fuel rail, there should be a vacuum line attached, check for fuel in the line, if there is fuel in there the fuel regulator is leaking and needs replacing.  

Update...

i done as sepulchrave suggested,  i put £30 worth of v-power in and some Redex and took it for a blast down the motorway. Twenty mile round trip at mostly 80 mph, i pulled well in all gears. i then went to my usual mechanic and got the codes cleared, i've been using it to get to and from work, short journeys.

I've just plugged the code reader in and i have only 1 code now, as follows.....

DTC01 - 16556 - Fuel Trim Bank 1 - Sytem Too Rich

 

No Warning Lights showing on dash

 

The mechanic at the garage said that usually points to the Pre Cat Lambda having failed ?

If thats the case why has it not triggered a warning light ?

 

I need to sort this as it will not pass it's MOT.

 

Thank you for the help and suggestions so far.

ECU temperature sensor needs replacing.

Do you mean the Coolant Temperature Sensor ?

 

Thanks.

Do you mean the Coolant Temperature Sensor ?

 

Thanks.

 

Yes, the one that talks to the ECU if yours has two of them.

But before changing that temp sender, double check that you have the correct fuel filter fitted, there are different filters with different pressure relief valves fitted in them, 3bar, 3,5 bar and 4 bar I think off the top of my head, doubt the temperature sensor will cause the fuel trim fault they usually go open circuit and log a fault

But before changing that temp sender, double check that you have the correct fuel filter fitted, there are different filters with different pressure relief valves fitted in them, 3bar, 3,5 bar and 4 bar I think off the top of my head, doubt the temperature sensor will cause the fuel trim fault they usually go open circuit and log a fault

 

No, they drift out of spec. as they age making the ECU think the engine is colder than it really is.

The cars done 4.5k since having the Fuel Filter and Pump replaced, would it have not shown up earlier ?

I've been and bought a Coolant Temp Sensor from VW , just need to fit it now.

 

In my opinion i think maybe the fault lies with the Pre Cat Lambda, i 've gone for the cheaper option of changing the Temp Sensor first, see how it goes.

 

Thanks for all the suggestions so far, i'll update when the new Temp sensor is fitted.

I've just had a quick look and it looks like there are 2 Pre Cat Lambda's, one on the top of the exhaust manifold and one lower down the lower part of the exhaust just before it goes under the engine.

I've ordered 1 Pre Cat Lambda at a cost of £141 from T.P.S. which is a genuine parts supplier for VW. Cant afford to buy another 1 at the moment, so which one do i change ? I'm assuming the lower one is also a Lambda sensor.

Does anyone know if it is or not ?

 

Thanks.

The one on top of the manifold is the pre-cat sensor, the other one is the post-cat sensor.  The round thing in front of the engine, connected directly to the exhaust manifold is the cat. 

 

Edit: what happened to the temp. sensor change plan?  Surely you tried that before forking out that amount?

 

Cancel your order with TPS and buy this one if you insist on genuine.

My apologies for taking so long. I've been in hospital, i wont bore you with the details but i'm fixed now..... sort of !

 

I replaced the pre cat Lambda and also the Coolant temp sensor at the same time. I noticed the car was running much smoother straight away, couldn't really tell if it was as heavy on juice.

The erorr - 16556 - Fuel trim bank 1 system too rich was still in the Ecu memory.

I cleared the code with my Gendan this morning, took it for a short spin (maybe 3 miles) and looked for the error when i got back.

My car is now showing "No Codes"

Fingers crossed and hopefully it doesn't come back.

 

Thank you to all who replied and offered their help, it was really was appreciated.