Glow plugs 101 ***Ver. 2.0***

Bill_Blazek

Veteran Member
Joined
Sep 28, 2004
Location
Littleton, Co
TDI
2002 Golf GLS TDI, 5 spd, Navy Blue
Jared,

If its starting a lot better now with new plugs then that's probably the problem.
You still should check the DTCs to make sure its not something else.
If it is the GP error it should clear right away.
It will not clear itself even after fixing the problem.
You have to clear it with the OBDII tool.

I have had the problem with the GP harness corrosion causing the GP error too.
In that case, the code just keeps coming back instantly as soon as you clear it.
Then either the harness needs to be replaced or
try some di-electric grease for the connectors in the harness.
Both are described in other posts above.
Its a good idea to use the dielectric grease to prevent the harness from
getting corroded in the first place.

I was getting the GP errors apparently due to the harness.
I had a hard time getting the code to clear.
This was very frustrating because the car always starts right up very easily.
The plugs show the proper resistance and the harness shows full voltage but
was still getting the error and turning on the CEL light which really bugs me.
I seem to have it fixed for now with the dielectric grease but probably will
have to replace the harness eventually.

Good luck.
 

dslemaire

Veteran Member
Joined
May 6, 2002
Location
Trumbull, CT
TDI
1996 Passat
I might add that I found why I was getting the CEL after changing glow plugs and harness. The connectors that are inside of the wiring harness for the glow plug harness actually backed out of the large round plug which has a lot of the control wires going through it. Not enough to notice, but enough to where sometimes it would work and sometimes it wouldn't. I pulled the wires out of the plug and spread the metal tabs on the connectors and pushed them back inside. No more CEL.
 

Keli_OR

Veteran Member
Joined
Nov 9, 2003
Location
West Linn, Oregon
TDI
'15 black Sportwagen SE, '01 silver Jetta GLS, '00 green Beetle
I'm saving this thread.

I feel like I've been in CEL purgatory!!!!


Keli
 

Paul_L_Fisher

Veteran Member
Joined
Aug 28, 2003
Location
San Tan Valley, AZ
TDI
None
One thing I tried sucessfully is using contact cleaner from Radio Shack. I had checked all the resistance and all GP's where the same. I sprayed in the harness and you could hear bubbling! Goodbye CE light!
 

STRANGETDI

Veteran Member
Joined
Sep 20, 2001
Location
East Hampton, CT
TDI
2013 Audi A3 S-Line Premium Plus Quattro - APR Stage II
One question: What is the part # of a new glow plug harness? I may need to go this route now. Thanks.
 

moondawg

Veteran Member
Joined
Oct 25, 2003
Location
Columbus, IN
TDI
2001 Galactic Blue Jetta
One thing I tried sucessfully is using contact cleaner from Radio Shack. I had checked all the resistance and all GP's where the same. I sprayed in the harness and you could hear bubbling! Goodbye CE light!
I also used this product. The first time I used it, it did NOT solve the problem. The second time I used it, I also used a small needle file to lightly file the inside surface of all of the glow plug connectors on the harness. This seems to have solved the problem.

The CEL is doubly bad on the MFA, because all of your useful information is covered up by the message "Emissions Workshop." it sucks.

Thanks wingnut for the cool how-tos!

moondawg
 

STRANGETDI

Veteran Member
Joined
Sep 20, 2001
Location
East Hampton, CT
TDI
2013 Audi A3 S-Line Premium Plus Quattro - APR Stage II
One question: What is the part # of a new glow plug harness? I may need to go this route now. Thanks.
Also, what is the kind of contact cleaner from Radio Shack? I may try that before I get a new harness.
 

moondawg

Veteran Member
Joined
Oct 25, 2003
Location
Columbus, IN
TDI
2001 Galactic Blue Jetta
The stuff I used comes in an Aerosol bottle with a detachable brush on the nozzle.

I picked up the needle file set at TSC (Tractor Supply Company) for $4.(yay CHINA!) It had 6 small files in it. I'm guessing the filing will solve the problem on its own.

moondawg
 

greenflyer

New member
Joined
Sep 27, 2005
Location
Washington
TDI
2002 Silver New Beetle
Glow Plug replacment

How do i find out which glow plug is which? I had my TDI scanned and they said it was the # 1 cylinder glow plug that needed replacing. And what kind of glow plug is it? or can i just replace it with any bosch glow plug?
 

ymz

Top Post Dawg
Joined
May 12, 2003
Location
Between Toronto & Montreal
TDI
2003 Jetta TDI Wagon, 2003 Jetta TDI Wagon
Glow Plug replacment

On your car, the computer "counts" the glow plugs in reverse order... so your "problem" GP is really # 4 - the one closest to the driver's side...

That said, the problem is quite likely corrosion inside the harness... needs a good scrubbing with a Q-Tip (minus most of the cotton) and an eletrical parts cleaner or anti-oxidant such as DeOxit D5... may need to be done several times, followed by a clearing of the CEL with either a Vag-Com or a generic OBD scanner...

BTW: did you check the resistance of the glow plugs? It could still be a bad plug...
http://forums.tdiclub.com/showflat.php?C...&PHPSESSID=
WingNut's "How-To" thread... see Glow Plugs 101...

You really should replace a Bosch with a Bosch and a Beru with a Beru, but the sky won't fall down if you don't...

Yuri.
 

Paul_L_Fisher

Veteran Member
Joined
Aug 28, 2003
Location
San Tan Valley, AZ
TDI
None
Re: Glow Plug replacment

#1 is the one closest to the timing belt. Right hand side when you are sitting in the car.

As for glow plugs themselves, go get Champion ones from Napa for under $20.
 

Spinergy

Member
Joined
Jun 30, 2002
Location
East Coast, USA
Thanks Wingnut and all the others on this forum who've contributed so much knowledge to this tdi newbie.

We too have this MIL glowplug error code issue. The first time it was for plug #2. Dealer replaced plug under warranty (at 49,9xx miles).

Two hundred miles later, and now out of the factory warranty, the MIL now shows plug #3 being bad.

Took the advice on here and went to Autozone to get a free reading. Read this thread and did the diagnostic - result is that the harness looks to be bad.

Here's some minor info for those who may have trouble following all of Wingnut's instructions.

1. When buying a DVM, I would suggest a Sears (Craftsman) or RadioShack version. I first went to Home Depot and got one. Being an electrical noob, the HD one was just a bit complex and I couldn't get it to work right. Got a Craftsman one and things turned out fine.

1a. Using the DVM - the black plug goes to "COM" and the red goes to "Ohm" (or the symbol for Ohm).

2. When you are measuring the glow plugs, you are measuring resistance. To measure resistance, the DVM provides an electrical charge via its internal 9V battery. If things don't seem to work, first test the DVM on a standard household lightbulb (one probe on the side of the metal screw-in base, one probe on the bottom end of the base) to make sure the DVM works. If things don't seem right, perhaps you have a dead or weak battery. Change it.

2a. When measuring the plugs, the numbers will jump around a bit until it settles at one point. My number for all plugs was 0.9 fyi.

3. The problems Wingnut suggest that we check are: (a) all glow plug resistance, (b) glowplug relay - does it send power to the harness (c) glowplug fuses and terminals under the battery cover and (d) the harness itself.

3a. Checking the relay is a bit of work, so I would check the fuses and battery things first - no need to do all that work if the fuses are bad.

4. So, if after checking the plug resistance and the 'under battery cover' items hasn't turned up a culprit, next is checking the relay.

4a. When I tried to unhook the coolant sensor, it was insanely difficult. Some tips: the sensor can spin somewhat in its location. When I first tried to pull it off, the little plastic clip that you must push down to unlatch it was oriented towards the passenger side of the car - making it impossible for me to use my thumb. My index finger could not put enough pressure on the clip to unhook it. You can try to spin the connector around so that the clip is under your thumb.

4b. As Wingnut noted, practice on the MAF if you need to. For those who haven't had a MAF problem, the MAF connector is the first plug you find along the accordion air tube, going from the airbox to the engine intake.

4c. If you need space to get to the coolant sensor clip, take off the accordion air tube. Note its orientation so you can put it back easily. If needed, use Vise grips to hold the metal band clamps open so you can use both hands when you are putting the tube back into the engine compartment.

4d. After getting the coolant sensor off (it took me about 1.5 hours, and I finally had to use a flat headed screwdriver to press the little locking clip), have someone else turn the engine key, so you don't have to run back and forth. Remember, you are just turning the key to power the electrical system. You don't turn on the engine.

5. All finished. If you need to replace the relay, it is located on the driver side, under a plastic cover, near the windshield/cowl. It is next to the brake fluid containder on our manual tranny 2002 golf.

6. If you have a bad harness, check to see if it is 2 or 4 wire. Our 2002 is a four wire harness. Find the link in Wingnut's post on how to replace.

7. If you want to clean the harness and not replace it, use the DeOXit or similar stuff discussed in the first post.

8. Clear the code using a VAG-COM or any OBD-2 scanner (aka at Autozone).

Good luck.
 

442guy

New member
Joined
Jun 5, 2005
TDI
Jetta, 2003, blue
I want to confirm that my 2003 Jetta had the glow plug codes reversed. I got a CE Light at 55,132 miles. Using Vag-Com it was showing that the glow plug on cylinder 4 was faulty.

I found that cylinders 4,3 and 2 were OK and tested at .6 Ohms. Cylinder 1 tested at infinity.

I replaced the Glow plug in cylinder 1 and re-set the code.

All is well in glow plug land .
 

STRANGETDI

Veteran Member
Joined
Sep 20, 2001
Location
East Hampton, CT
TDI
2013 Audi A3 S-Line Premium Plus Quattro - APR Stage II
I went to impex and ordered it. Now my question is splicing the wires. Since I don't have it yet, does it matter which wires get hooked up to the other 2 wires? Are they interchangeable?

I'll post pics of what happened to my harness (glad I caught this before winter sets in) when I do the swap.
 

ymz

Top Post Dawg
Joined
May 12, 2003
Location
Between Toronto & Montreal
TDI
2003 Jetta TDI Wagon, 2003 Jetta TDI Wagon
>>does it matter which wires get hooked up to the other 2 wires?<<

Are you trying to say you got a 4-wire harness??? The one for the 1999.5 has only 2 wires... In any case, the wires are all "hot"... in principle you could just short them all together... and will never get a CEL for a bad GP again...

Just make sure you waterproof (moisture-proof) the connection!!! Either use crimp-type connectors from an RV store, or tons of shrinkable tubing... (again, if you can get it from an RV store, they have the type with glue inside...)

Yuri.
 

STRANGETDI

Veteran Member
Joined
Sep 20, 2001
Location
East Hampton, CT
TDI
2013 Audi A3 S-Line Premium Plus Quattro - APR Stage II
No,

Sorry, I wasn't clear.
I have a 2 wire harness and ordered a 2 wire harness (at least that is what the picture showed on Impex). Can I splice either wire to the other when I change it? Does it matter?
 

sed11

New member
Joined
Oct 30, 2005
Location
Chattanooga, tn
TDI
2003 jetta
I have a 2003 jetta. Glow plugs will not come on. Unplugged coolant temp sensor. They came on for 10 secs. Replaced coolant sensor, still do not come on. No codes. Checked voltage at plugs with sensor unplugged & have 12 volts to all. Any suggestions???
 

rdkern

Top Post Dawg
Joined
May 21, 2004
Location
Humboldt Co CA
TDI
Passat 1997 silver (sold after 11 years), Jetta 2000 atlantic blue
The gplugs aren't suppose to come on below 40 F or so. If you're close to that, you might be able to reset the temp sensitivity with Vag-Com. If you're above that, your car is working normally.
 

STRANGETDI

Veteran Member
Joined
Sep 20, 2001
Location
East Hampton, CT
TDI
2013 Audi A3 S-Line Premium Plus Quattro - APR Stage II
No,

Sorry, I wasn't clear.
I have a 2 wire harness and ordered a 2 wire harness (at least that is what the picture showed on Impex). Can I splice either wire to the other when I change it? Does it matter?
Can anyone answer this?

Also, here is the harness I got from Impex yesterday.

 

tditom

Top Post Dawg
Joined
Sep 5, 2001
Location
Jackson, MI
TDI
formerly: 2001 Golf GL, '97 Passat (RIP) '98 NB, '05 B5 sedan
This does matter, otherwise you would be putting 12 volts to the block, no? It looks like there is a white stripe on one of the leads. Does the original harness have this stripe?
If there is any question, I would use and ohmmeter and check for continuity to the center contact of one of the sockets- the lead that contacts the middle of the GP top.
-tom
 

Wingnut

Top Post Dawg
Joined
Oct 10, 2002
Location
Toronto & Whitby
TDI
Silver 2003 Jetta Wagon
That white stripe is not there. It is just the reflection from the flash.

It does not matter which wire attaches to which wire. Both wires simply feed 12v to the plugs....2 plugs for each wire. The other end of the plug is grounded to the block.
 
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