How to Reset Check Engine Light

JettaTDI2000

Well-known member
Joined
Oct 27, 2002
Location
Illinois, U.S.A.
TDI
Jetta TDI, 2000, Black
Hi,
is there a way to reset the Check Engine Light without using speacial tools? I had Auto Zone read the code for me, but they won't reset the light, so I need to do it myself.

Thanks
 

HopefulFred

Veteran Member
Joined
Sep 5, 2002
Location
Atlanta, GA
TDI
Golf, 2006, Indigo Blue
some of them will go away after some number of starts - it depends on the code and condition (if the condition persists, obviuosly, CEL will too).

The "right" way would be with a VAG tool, but if you had that, you wouldn't have gone to AutoZone would you...


I would bet for a temorary code, disconnecting the battery for a reasonable length time (I think it needs to be more than just a second or two) would speed the process along. Of course, you'd have to reset your radio presets.
 

Toronto_Vento

Top Post Dawg
Joined
Nov 7, 2002
Location
Richmond Hill, ON
TDI
01 Baltic Green Bora
Did you fix the problem? If so, put the key to on position, wait for the glowplug light to turn off, then turn key to off. (don't start the car) Repeat this 3-5 times. Sometimes this will reset the code, as the ECM has then fired up 3-5 times without detecting the problem. Otherwise you will need someone with a Vag-Com to reset the code (which is the better way to do it).
 

alanmcd

New member
Joined
Jan 9, 2005
Location
PA, USA
TDI
jetta, 99, silver
I have a 1999 Jetta TDI with the new body style wiht a check engine light active. I have tried to disconnect the battery and do the trick of turning the key on (5-7 times without turning the engine over) and letting the glow plug light go out. Nothing seems to work to reset the CEL. Any other ideas besides getting it reset with the electronic device? Also, I did not loose my radio presets. The only indications that I noticed was the tripometer reset to "0".
 

MOGolf

Top Post Dawg
Joined
Jun 27, 2001
Location
underneath something
TDI
2001 Golf GLS TDI Reflex silver, rough road suspension and steel skid plate, 2004 Passat Variant, Candy White, rough road suspension and geared balanced shaft module, and much, much more. 2016 LR RR HSE TD6, 2019 Jaguar I-PACE
alanmcd, you need to (1) find out why the light is on, (2) fix it, then (3) find someone with a software interface that can clear codes. None of the things you tried will ever turn off the light.
 

BioDzel

New member
Joined
Aug 1, 2003
Location
San Diego, CA
TDI
Golf TDI GLS, 2003; Passat TDI SEL, 2014
JettaTDI, you said Autozone read the code, but won't reset the code for you--can you just borrow the OBDII scanner, take it out to your car, and reset it yourself? That's what I did after installing my RocketChip (which Jeff warned me would cause the CEL to go on).
 

onehotspud

Veteran Member
Joined
Aug 2, 2004
Location
Grand Rapids, MI
TDI
2001 Jetta TDI
The way that I would get autozone to reset mine is:

1. Ask them to scan and give you code
2. Leave
3. "Fix it"
4. Go back and say that you "Fixed it" and ask them if they will clear it for you

Mine were all glow plug failures. And one MAF failure (I unpluged it and forgot to plug it back in before I started it). Nothing serious. As MOGolf said, if it is a real problem, get it fixed first. Sometimes those codes really are something.
 

GoFaster

Moderator at Large
Joined
Jun 16, 1999
Location
Brampton, Ontario, Canada
TDI
2006 Jetta TDI
Something to re-iterate:

You can NOT turn off the MIL (aka "check engine light") without first ACTUALLY fixing the underlying problem. If you don't fix the underlying problem, it will either not be possible to reset the code, or it will reset temporarily but come back as soon as the fault gets detected again.

As for disconnecting the battery ... this persists from the early days of automotive electronics, even though there are far more vehicles with OBD-II on the road now than there ever were with older systems. On any vehicle with OBD-II, faults are stored in permanent memory. You could disconnect the battery for 1.3 million years, and it will still remember it.

Sometimes fixing the actual fault is easy, sometimes it isn't. I've forgotten to plug in the MAF, too ... that was an easy one.
 

Joe_Meehan

Top Post Dawg
Joined
Sep 3, 2005
Location
Ohio USA
TDI
NB TDI, 2002.5, Silver
alanmcd, you need to (1) find out why the light is on, (2) fix it, then (3) find someone with a software interface that can clear codes. None of the things you tried will ever turn off the light.
The light is no a Christmas tree it has a real purpose in life. The question is NOT the light. The real question is why did the light come on.

Fix the real problem then the light will go away and the real problem along with possible damage to your car or our safety.
 

jettawreck

Top Post Dawg
Joined
Aug 2, 2004
Location
Northern Minnesota-55744
TDI
2001 Jetta and 2003 Jetta
I did the key off an on trick the light went out for how long who knows???
At least for about as long as the problem/issue stays away.....;)
Get it scanned properly w/VCDS and depending on the code(s) results, get the issue(s) repaired. Or, it'll be back-again and again.
 

dieselkid96

New member
Joined
Jan 14, 2015
Location
OH
TDI
01 mk4 jetta GL 5 speed
What if the CEL is related to a complete egr delete and a true straight pipe exhaust, is there anyway to turn it off with VAG-COM?
 

JSWTDI09

Top Post Dawg
Joined
Jan 31, 2009
Location
Las Vegas, Nevada
TDI
2009 JSW TDI (gone but not forgotten)
What if the CEL is related to a complete egr delete and a true straight pipe exhaust, is there anyway to turn it off with VAG-COM?
No. The CEL will not go away if the cause of the CEL does not go away. I believe that a custom ECU tune is the only way to modify the emissions system without a CEL of some kind.

Have Fun!

Don
 

supton

Top Post Dawg
Joined
May 25, 2004
Location
Central NH (USA)
TDI
'04 Jetta Wagon GLS
The straight pipe should not matter. At least through the PD models calalyst efficency was not monitored.

On the older VE's there was (is?) a way to modify the wiring slightly; want to say a diode is involved, that "fakes" the system into believing that EGR is working. Otherwise a tune is required. On my PD the O2 sensor knows if the EGR is working, and thus a real tune is required.
 

Dieselista

Active member
Joined
May 1, 2008
Location
Virginia
TDI
06 Jetta, 03 Bug, 74 TR6, 92 Ducati 907ie, 96 F250 PowerStroke
Check engine light

Got the check engine light, went to AZ, they scanned it and the print out said P0671 Cylinder 1 glow plug circuit.
I checked the connections, removed and reconnected, and they seem good, no corrosion. Have not yet checked glow plug resistance.
Is this likely to be a deteriorating glow plug, or wiring, or controller? Looks like a separate wire for each plug, which is not what I'm used to on other (marine) diesel engines. The black harness around the glow plug wires is cracking, but that just looks like a chafe guard, not really part of the system electrically.
Tips on clearing the light to see if I've fixed it?
Also, what is the diaphragm like device with lever, passenger side back of engine, looks like it's part of turbo control? It has a small telltale hole that I'm getting a little bit of black oily liquid out of, not much.
 

KLXD

Top Post Dawg
Joined
Aug 22, 2009
Location
Lompoc, CA
TDI
'98, '2 Jettas
Sounds like the EGR valve vent hole. Indicates the seal on the shaft between the manifold and atmosphere is leaking. Live with it or buy a new EGR valve. Don't plug it.

You "checked" everything but the likely failure. Did you read any of the previous posts? Buy or borrow VCDS to clear the code. Maybe a generic scanner will do it. Maybe AZ will try.
 

Dieselista

Active member
Joined
May 1, 2008
Location
Virginia
TDI
06 Jetta, 03 Bug, 74 TR6, 92 Ducati 907ie, 96 F250 PowerStroke
Re. the EGR, I'll monitor, if/when it gets worse I'll replace. I wouldn't plug a telltale, they are there for a reason.

"the likely failure", I did read all of the posts in this thread, unless I missed it none indicate what might generate such a code for a glow plug, all seem to center on clearing it, hence my question. What's the most likely cause, a bad connection, glow plug controller or the plug itself?

I infer from your response that the only way to clear the CE light is to use a VCDS, obviously after I believe I've fixed the problem.
 

Vince Waldon

Top Post Dawg
Joined
Apr 25, 2009
Location
Edmonton AB Canada
TDI
2001 ALH Jetta, 2003 ALH Wagon, 2005 BEW Wagon
There's a massive "Glowplugs 101 V2" thread that will tell you everything you need to know about tracking down glow plug issues.

One hint... they are numbered opposite of the cylinder bank... so #1 is on the drivers side.

Yes, measuring the resistance of the glow plugs is a great next step.

Yes, an OBD2 scanner (like VCDS) is the only way to reset the CEL.
 

Ol'Rattler

Top Post Dawg
Joined
Jul 3, 2007
Location
PNA
TDI
2006 BRM Jetta
Some just plain old nonsense mythes about a modern VW ECU:
  • You don't need VCDS to clear OBD2 codes. Any generic OBD2 scanner can do it.
  • Disconnecting the battery will not clear codes.
  • Cycling the key several will not clear codes.
Disconnecting the battery invalidates readiness and once readiness tries to reset and it can't if the problem is still there, the code will come back. The code may not come back for a while until the same operating conditions occur that set the code it the first place. (Intermittent problem)

The great news is that you found some solid factual information about your glow plug issue.:cool:
 
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