Dealing with the 'Preheat Fault' message [Stilo JTD]

zstef

Glow plugs (or heater plugs) are used to warm the cylinder on cold mornings when starting a diesel. Unlike spark plugs, which are used continuously in an engine and therefore wear out over time, a glow plug is more like a light bulb and they either work perfectly or they don’t work at all.

Change just one or should I change all 4?

Maybe you have a light fitting with 4 candle lit bulbs in your home. If one day you looked up and noticed a bulb had failed would you then decide to buy 4 new bulbs in the morning and change all 4. I suspect most wouldn’t and the same principal applies to heater plugs (but there’s always somebody

).

Tools required: a reasonable car tool kit and a multimeter

Procedure

1 Remove engine cover.

2. Disconnect the glow-plug relay heater module from the bulkhead. The module is directly behind the EGR valve and attached to the bulkhead with a single 10mm nut. Now carefully manoeuvre the relay module to allow access to the connectors on the rear.

3. You must remove the larger cable (4 thick coloured wires). With one hand hold down the release spring and with the other pull the connector free.

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4. Now set your multimeter to Ohms Ω on the lowest resistance scale. Make sure one probe is held on the engine and with the other probe carefully touch pins 1,2,3 & 4 of the plug (as shown) in turn. You should get a reading of about 1.2 ohms on each connector. If you don’t get a low reading (meaning you get a very high or ‘open circuit’ reading) then make a careful note of which pin # it is. Try several times (it’s easy to get an ‘open circuit’ reading if one of the probes slips) and make sure the pin that gives no reading on the meter is always the same one.

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5. Now use this simple table to work out which cylinder has a faulty glow-plug

Pin 1 (YELLOW) = Cylinder 4
Pin 2 (BLACK) = Cylinder 3
Pin 3 (GREEN} = Cylinder 2
Pin 4 (RED) = Cylinder 1

Note: cylinder 1 is always furthest from the flywheel or if you prefer is next to the cam belt cover

6. Reassemble everything but don’t bother replacing the engine cover.

Contact your favourite Fiat garage, and get a quote for replacing a single glow plug (tell them you’ve already removed the engine cover if you like). It doesn’t have to be a Fiat garage as long as they’re quite competent. It should be a half hour job so expect to pay a labour charge of between £15 to £40. The glow plug itself is only about £15 and my local Fiat specialist only charges £30 for the whole job. Tell the garage VERY clearly which cylinder needs a new glow-plug.

Hopefully, the garage should report that you correctly diagnosed a faulty glow plug. They’re very easy to test as you only need connect the plug across a spare car battery. If it glows red hot then something has gone wrong and you should make sure they really have replaced the one you asked them to.

Q & A
Q1: What if all the heater plugs read correctly.
A. This means either the heater relay module is defective or you have a bad connection somewhere. I’d spray the plug contacts with electrical cleaner and reassemble. You may well find the problem has gone.

Q2: The garages says I diagnosed a faulty glow-plug correctly (take a bow

) but want to charge me to reset the stored error code.
A. Like all Stilo errors, the warning will disappear after 3 good starts. Don’t pay for a reset (or at least wait until you have some major work done with Examiner)

Q3: I’m pretty flush at the moment and can’t be bothered with all this diagnosis stuff. I’m just going to tell the garage to change all 4!
A. You might look a bit silly if all 4 plugs turn out to good (see Q1). Why are you reading this anyway

Q4: What do they look like?

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OzMoSiS · 24-06-2008

good write up and much appreciated argo

all we need now is someone to write a guide on actuall changing the plugs

Argonought · 24-06-2008

Thanks Oz,

I've just come back from the garage after having No. 1 changed. Only cost £15+VAT as I supplied the glow-plug myself

They told me that changing 2 & 3 is a lot easier than changing 1 & 4 (so that's why it took so long

)

As you say, all we need now is for someone to give it a go

minimad99 · 26-06-2008

Nice one Argo,
Another downside to having a strutbrace fitted

it's right in the way of the module.

Pedz · 13-11-2008

is there a guide on actuall changing the plugsor a gd picture??

Argonought · 19-11-2008

Originally Posted by Pedz

is there a guide on actuall changing the plugsor a gd picture??

I don't think a single member has managed to change one successfully yet

- other than Fiat Techs of course

Be warned that someone did have a go but ended up with their car being off the road for a while (damaged the injection pipework)

Having the correct tools is critical.

PhilM Star · 11-03-2009

I have managed to change one of the four, the one on the green wire. It was pretty straight forward but I had to disconnect the fuel lines and buy a long reach 10mm socket. The hole for the plug is quite a way down and on my first attempt the new plug fell off the socket and went down behind the engine. I had to get underneath to reach up and retrieve it. the second time I put a small amount of paper round it so it was held more firmly by the socket. Take care not to use too much that it might go into the engine. Just a very fine strip around the actual hex shape that the socket goes on. I was very carefull not to cross the threads as stripping these is going to be a real pain.

I think some of the others may be more fiddly but do-able. The plug was very cheap off e-bay. Halfords dont stock the one for a 1.9 JTD

robbie-rocket-pants · 25-05-2009

Hello chaps,
this is an excellent guide. Thanks.

I managed to change the glow plug on cylinder 4 (yellow wire, connector 1) fairly easily, but be prepared to skin a knuckle or two:

1. Undo plastic engine cover and remove it.
2. Find glow plug by looking behind inlet manifold - it's hidden below the waste-gate valve area.
3. Undo 10mm bolt holding coolant return pipe which is above the glow plug and move the pipe to one side.
4. Get your hand in the tiny gap below the waste-gate and pull the electrical connector off the glow plug. (This is the trickiest bit - you may be able to use another method)
5. Use a deep 10mm socket to remove the old glow plug and replace with new one using the piece of paper trick mentioned in the above post.
7. Replace the electrical connector by resting it on top of the glow plug then pushing it firmly down by using the 10mm socket.
8. Replace coolant pipe & engine cover.
9. Start engine, but don't get dis-heartened if you get the "Preheat" warning as it takes a few good starts for the warning to go away.
10. Have a beer.

Cheers,
RRP

robbie-rocket-pants · 27-05-2009

p.s. Glow Plug is NGK Y-534J

maloon · 26-06-2009

i had the preheat fault on a 2003 jtd stilo and after checking glow plugs and getting a even reading across all plug, traced the fault back to a blown fuse on the battery box (a big red maxi 50a fuse). worth checking if you get the fault

Argonought · 16-11-2009

Originally Posted by maloon

i had the preheat fault on a 2003 jtd stilo and after checking glow plugs and getting a even reading across all plug, traced the fault back to a blown fuse on the battery box (a big red maxi 50a fuse). worth checking if you get the fault

Good call on Fuse F4

Just had this myself. An easy check is to measure 12 volts on the main supply line to the heater relay unit (looks like a big earth cable - but it isn't)

punto60_s · 24-01-2010

Thanks so much for this! Successfully diagnosed cyclinder 3 glow plug was dead, got the plug from shop4parts and changed today, its a pig of a job but if you've got a good set of tools and a girlfriend with small nimble hands cylinder 3 is certainly doable, wouldn't like to do it again though.

P.S. - I was worried about the glow plug snapping as I had been told by a few garages that they tend to snap, well the one I did was not a problem, came out really easily!

Again Thankyou.

cledan · 22-08-2010

Originally Posted by Argonought

I don't think a single member has managed to change one successfully yet

- other than Fiat Techs of course

Be warned that someone did have a go but ended up with their car being off the road for a while (damaged the injection pipework)

Having the correct tools is critical.

Thanks for the guide, very useful, I changed number 3 glow plug, only bought 1 (re your OP) but then found 2 were down after running your check...
Only thing was I'm sure I changed the wrong one, 2 were fine, 1 was completly open and 1 was reading 243 or so...Maybe I got confused about the wire sequence

Anyway I made a little puller tool that flicks off the caps with only the engine cover removed, so you could drop the multi meter probes straight on the glowplug.
All it was, was one of the stainless steel ribs out of an old wiper blade, bent 10mm from the end, and bent 10mm from that bend, pops em off a treat

Any one else thinking of doing this, be carefull about removing the plugs, as they are screwed into ally, and this will strip very easily if you are not very careful

pwoodiwi · 06-11-2010

Great test proccedure and guide, takes about 10 min to test & 20 to change (no 3 plug) would recommend you make a soft wire loop to get the old plug out when unscrewed and locate the replacement. If the loop is a snug fit you can start the thead before using the 10mm deep socket.

Worst part was removing / repacing electrial connection!!

mattlindsay · 13-05-2011

Woooo hooooo

Just got Cylinder 4 fitted (with my part off ebay) for under 25 quid.... fixed the issue! Saved myself an absolute bundle thanks to you Argonought. Thanks you so much!!!

24-06-2008	#1
OzMoSiS Get Your Own Title Join Date: Jan 2007 Location: Cairo, Egypt Posts: 1,158 Thanks: 32 Trader Rating: 3	Re: Dealing with the 'Preheat Fault' message [Stilo JTD] good write up and much appreciated argo all we need now is someone to write a guide on actuall changing the plugs __________________ Originally Posted by dan-the-man i only have one nipple *Check out my items in the classifieds section* *HERE*
	Quote

24-06-2008	#2
Argonought It's about GO! not SHOW! Join Date: Sep 2005 Location: POOLE, Dorset Posts: 7,334 Thanks: 329 Blog Entries: 1 Trader Rating: 0	Re: Dealing with the 'Preheat Fault' message [Stilo JTD] Thanks Oz, I've just come back from the garage after having No. 1 changed. Only cost £15+VAT as I supplied the glow-plug myself They told me that changing 2 & 3 is a lot easier than changing 1 & 4 (so that's why it took so long ) As you say, all we need now is for someone to give it a go __________________ ------------------------------------------------------ Stilo Dynamic 5 door JTD {150} 02 model in Metallic Grigio Steel with Skyroof & 16" Alloys Mods: New standard springs all round; Tyres: Pirelli P7; Pads: EBC GreenStuff; Oil: Mobil 1 TD 0W-40 fully synthetic
	Quote

26-06-2008	#3
minimad99 Driver Extraordinaire Join Date: Sep 2004 Location: Rustington, West Sussex Posts: 1,085 Thanks: 35 Trader Rating: 0	Re: Dealing with the 'Preheat Fault' message [Stilo JTD] Nice one Argo, Another downside to having a strutbrace fitted it's right in the way of the module. __________________ 3 Door Sprint Blue JTD with Skyroof, 17 inch Fox R1 alloys, -30mm Eibach Springs Boge Turbo shocks, OMP Strutbrace, RED.DOT 6 Grooved discs front and rear with fast road pads RED.DOT RACING TUNED - to 153BHP / 201FTLB TORQUE
	Quote

13-11-2008	#4
Pedz Get Your Own Title Join Date: Oct 2008 Location: Perth Posts: 33 Thanks: 2 Trader Rating: 0	Re: Dealing with the 'Preheat Fault' message [Stilo JTD] is there a guide on actuall changing the plugsor a gd picture?? __________________ Thanks Pedz
	Quote

19-11-2008	#5
Argonought It's about GO! not SHOW! Join Date: Sep 2005 Location: POOLE, Dorset Posts: 7,334 Thanks: 329 Blog Entries: 1 Trader Rating: 0	Re: Dealing with the 'Preheat Fault' message [Stilo JTD] Originally Posted by Pedz is there a guide on actuall changing the plugsor a gd picture?? I don't think a single member has managed to change one successfully yet - other than Fiat Techs of course Be warned that someone did have a go but ended up with their car being off the road for a while (damaged the injection pipework) Having the correct tools is critical. PhilM Star thanked for this post __________________ ------------------------------------------------------ Stilo Dynamic 5 door JTD {150} 02 model in Metallic Grigio Steel with Skyroof & 16" Alloys Mods: New standard springs all round; Tyres: Pirelli P7; Pads: EBC GreenStuff; Oil: Mobil 1 TD 0W-40 fully synthetic
	Quote

16-11-2009	#10
Argonought It's about GO! not SHOW! Join Date: Sep 2005 Location: POOLE, Dorset Posts: 7,334 Thanks: 329 Blog Entries: 1 Trader Rating: 0	Re: Dealing with the 'Preheat Fault' message [Stilo JTD] Originally Posted by maloon i had the preheat fault on a 2003 jtd stilo and after checking glow plugs and getting a even reading across all plug, traced the fault back to a blown fuse on the battery box (a big red maxi 50a fuse). worth checking if you get the fault Good call on Fuse F4 Just had this myself. An easy check is to measure 12 volts on the main supply line to the heater relay unit (looks like a big earth cable - but it isn't) __________________ ------------------------------------------------------ Stilo Dynamic 5 door JTD {150} 02 model in Metallic Grigio Steel with Skyroof & 16" Alloys Mods: New standard springs all round; Tyres: Pirelli P7; Pads: EBC GreenStuff; Oil: Mobil 1 TD 0W-40 fully synthetic
	Quote

24-01-2010	#11
punto60_s Stilo JTD 115BHP Join Date: Dec 2006 Location: Northumberland Posts: 204 Thanks: 20 Trader Rating: 0	Re: Dealing with the 'Preheat Fault' message [Stilo JTD] Thanks so much for this! Successfully diagnosed cyclinder 3 glow plug was dead, got the plug from shop4parts and changed today, its a pig of a job but if you've got a good set of tools and a girlfriend with small nimble hands cylinder 3 is certainly doable, wouldn't like to do it again though. P.S. - I was worried about the glow plug snapping as I had been told by a few garages that they tend to snap, well the one I did was not a problem, came out really easily! Again Thankyou. __________________ Navy, Fiat Stilo JTD 115 bhp, 17' alloys, Side Skirts, Spoiler - Excellent Fun!!
	Quote

22-08-2010	#12
cledan Get Your Own Title Join Date: Aug 2010 Location: mid wales Posts: 135 Thanks: 2 Trader Rating: 0	Re: Dealing with the 'Preheat Fault' message [Stilo JTD] Originally Posted by Argonought I don't think a single member has managed to change one successfully yet - other than Fiat Techs of course Be warned that someone did have a go but ended up with their car being off the road for a while (damaged the injection pipework) Having the correct tools is critical. Thanks for the guide, very useful, I changed number 3 glow plug, only bought 1 (re your OP) but then found 2 were down after running your check... Only thing was I'm sure I changed the wrong one, 2 were fine, 1 was completly open and 1 was reading 243 or so...Maybe I got confused about the wire sequence Anyway I made a little puller tool that flicks off the caps with only the engine cover removed, so you could drop the multi meter probes straight on the glowplug. All it was, was one of the stainless steel ribs out of an old wiper blade, bent 10mm from the end, and bent 10mm from that bend, pops em off a treat Any one else thinking of doing this, be carefull about removing the plugs, as they are screwed into ally, and this will strip very easily if you are not very careful __________________
	Quote

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