Failed Glow Plugs Lead To Limp Mode

[south_bound]

So last week I found out that if the glow plugs fail then this throws the Focus into limp mode, with no codes to help diagnose this. This happened to me just after filling up with diesel in the south of France and a ferry to catch in Calais the next day, just before a bank holiday when everything would be closed (and this being France I mean everything). Didn't know what it was but took the risk and drove on as fast as the car would allow, which was about 65mph on the flat at 30mph going up hills. The worst thing was in town as I just couldn't pull out until there was a huge gap in the traffic, and no cheeky lane changes...glad to make it to the ferry though.

Back in the Uk the first guy I saw couldn't pull out any codes so changed the fuel filter and crossed his fingers. To be honest he is a good mechanic but probably not too good on the computer side of things. Then I carried on and went to Avon Tuning near Bristol who I have used before and they did the business, diagnosed the problem and changed out the glow plugs. There were some EGR codes so I got that blanked and deleted from the ECU as well. I had already bought the blanking plate but never got around to fiitting it. Suffice to say it all works great now, better than it was before the limp mode came on. A big thank you to Gareth, James and the crew at Avon Tuning for their efforts. They now also do Terraclean so I will be calling back there sometime soon after all the good things.

So anyway, why do Ford prgramme the car to go into limp mode (I assume to protect the engine system) over something which does not even affect the driving? No codes, no nothing to help work it out. Now, I have since read on this forum about this, but didn't have the time or facilities to do that while on the road and under pressure to get to the other end of the drive in one piece. To cap it all off, the trip back ended with a cracked windscreen and a/c stopped working - just not my week.

[JW1982]

On modern diesel engines the glow plugs are not only used for starting the engine. The glow plugs are also used during normal operation and driving. The reason of this is to make the engine run smoother and reduce emissions.

A defect of the glow plug system should generate DTC codes. Most times such manufacturer specific codes can only be diagnosed with manufacturer specific diagnostic system. Generic diagnostic systems do not show all DTC codes. These systems will only show the mandatory codes described by European law.

[south_bound]

Thanks for the explanation.I did find it strange that having no glow plugs didn't affect the car starting at all.

I didn't get any codes at all using the on board dash trick or a cheap OBD reader, nor did the first garage with a more professional system. I think the guys at Avon use IDS which if I understand right is as close as you can get to the manufacturer's system and even then it took a few goes to confirm the issue. I didn't know there was a list of EU approved codes which the manufacturers have to follow, so that is worth knowing.

Anyway, I hope this post can help someone who has the same problem and doesn't know what to look for - its a cheap fix if you know what to look for.

[simcor]

IDS is the Ford diagnostics program, if the Glow plugs have failed a DTC should be stored, mine stored a DTC for the glow plugs when they went on mine. The only way to check them is to do a resistance test if no error codes are shown to see if they are duff or not. If they check out fine then it is being caused by something else.

[south_bound]

Agreed, easy to test as long as you identify that they could be the issue. Without access to the fault code or loads of research I wouldn't have even thought to check them in the first place. My inital thought would be that the car starts fine so it wouldn't be the glow plugs, but now I know better LOL.

[TomsFocus]

One benefit of direct injection is that you don't 'need' glowplugs to start, even in cold weather. You'll never start an indirect injection diesel without!

That said they do help, and are used after start-up and during DPF regen, so are still useful!

[pads18]

Thank you ever so much for posting this, It has helped me out big time.

I know it's an old post but still ever so helpful.