My 55 Focus Mk2 Diesel engine light is on, and the acceleration/power is reduced. The light sometimes goes off and full power is restored, when I get to a higher speed. As soon as I drop back to street speeds, the light comes back on and the power/acceleration reduces. My car has covered 80k, much of which has been only local driving during recent years. I've tried using the Wynns diesel EGR 3 air intake cleaner to clean the EGR valve and Mass airflow sensor. I've also changed the air and fuel filters, which weren't that dirty and have been changed regularly.

I get the feeling the fault might be close to resolving itself seeing as it clears at higher speeds, and I'm wondering if I just need a good long run in order to heat and clear the system.

I've been slightly reluctant to go to the expense of a code reading, but I appreciate that this could be the only solution in order to identify the problem. This is my next move, unless someone could suggest some DIY remedies.

Any suggestions/experience would be greatly appreciated, including which budget OEBD scanner to buy.

How old is the fuel filter ?

Does the car have a DPF or a CAT ?

A code reader is only about £15

Thanks for the prompt replies. The fuel and air filters are brand new and the 1.8 Focus Mk2 turbo diesel has a CAT.

Do you know where I can I get a code reader for £15.00, and will it do the job?

If its a turbo diesel.. surely it won't have a cat?

Ford diesels had cats until about 2008 / 9

My 05 Mondeo ST TDCi had a cat

Ebay for OBD2 readers

Ah, fair enough! Learn something new everyday

New mondeo has a cat, a dpf and a nox trap. ! Sounds expensive when that lot packs up.

Come on guys, there must be someone out there with constructive comment. I tried out a cheap ebay code reader, but no codes show up. The cars on board system check was a bit more helpful, giving two codes 9318 (low voltage) and A103 (Antenna not connected, defective transceiver) A battery check rules out the low voltage, and I'm not sure how to check the other. Any suggestions?

The antenna thing is probably from factory when they initialise modules for the first time before everything is fully fitted.

I'd reset that and see if it comes up again.

Low voltage could just be battery related, I'd check voltage when running which should be over 14v.

If below 12v I'd suspect alternator.

Has the car ever had a new battery? If yes is it a silver calcium one?

The alternator has been renewed recently and the battery is sound. I've done a voltage check to the battery using a multimeter, and it functions as it should. I've been chasing any information that might give a clue to the cause, and a few things may have some relevance such as, the glow plugs might need replacing, the CAT might need a clean, the EGR might need stripping and cleaning and there might be a dirty or dodgy connection on the instrument cluster. I'm not sure about the idea of blanking the EGR off, as it must be there for good reason. I'm determined to get to the bottom of this, like a dog with a bone! I was amazed to view a YouTube footage of a guy with the exact same problem with regards to the code reader check. He even had the same basic meter, which indicated 'no codes' and yet the engine light kept coming back on only seconds after cancelling. He also had the A103 and 9318 codes on the cars own check system. Unfortunately, the guy doesn't actually resolve anything, but at least I know others are having a similar experience.

I'd love to hear from those of you who have also had similar experience, and what you did to resolve it.

The only reason the EGRV exists is to lower Nox emissions, by blanking it you will save your turbo from an early death & extend the life of your engine

Ok. To blank or not to blank, that is the question! I might just try a blast down the bypass and try to warm/free things up, though I'm a little concerned that I might damage the engine. Apparently, if I have good oil compression there shouldn't be a problem. If this fails, it only leaves the dreaded garage diagnostic check, for whatever price they want to rip me off with. Such is life!.

Cheers to all those who commented.

I had similar issies recently, except that the engine light and limp mode stayed on permenently and no codes showed up at all. The cause in my case was glow plugs - apparently they can fail one at a time but only throw the car into limp mode when the last one goes. Glow plugs are easy enough to check but can be a pain to pull out without breaking the tips off so be careful if you are doing this yourself. I got the EGR blanked and deleted on the ECU at the same time which I have been meaning to do for a while now and there is a noticeable difference (in a good way) in how the car drives. I can recommend a specialist in the south west of England if you want - can't see where you are based.

Thx for the info. I'll investigate my glow plugs, which have covered 83k. I suppose I discounted the glow plugs initially cos I've had no problems with starting or idle, unlike how faulty spark plugs might have reacted. I'll investigate how best to remove them with minimum risk of damage. Once I see the effect of changing them, I'll consider the EGR blank. Thanks again.

Should have mentioned, I'm in Formby, NR Southport and Liverpool.

No problem - I was releived when it was just glow plugs which needed doing, could have been a lot more expensive. I was surprised to learn that modern diesels don't really need glow plugs to start the engine (the proof is that mine started no problem with all of them cooked) but they have a function to do with emissions control while running (but don't aks me for more detail than that!)

Waiting for delivery of my new Bosch Glow Plugs from micksgarage.com for the best price of £7.61 each. There's even a £5 discount if you sign up for the news letter. They should arrive today, so I'll keep you informed. My experience seems to be similar to that of yours, in that the car has been both starting and idling ok. There is a discrepancy between the plugs when I do the ohms meter test, though I'm not certain I've done that correctly. I do know they're not all the same reading, in which case I'm changing them all.