Check engine & glow plug lights, what does it mean?

Karen Abse

Member
Joined
Jan 11, 2003
Location
Richmond, Virginia
TDI
Passat 1996 green
My '96 Passat missed a couple times then the "check engine" light came on. It smoothed out, the "check engine" light remained on but then the glow plug light started its flashing as well. What does this mean? Do I need new glow plugs? Karen
 

Toronto_Vento

Top Post Dawg
Joined
Nov 7, 2002
Location
Richmond Hill, ON
TDI
01 Baltic Green Bora
No, this actually has nothing to do with your glowplugs. It means that a sensor didn't like something, and it stored a code in the computer. You'll have to get your computer scanned in order to clear the code as well as find out what the issue is.

BTW, do you know if there are any modifications done to the car (such as a tuning box) or if you are running bio-diesel? Both of these MAY cause a sensor called the N109 to not like something, and give you the check engine light with the flashing glowplug light. Just a thought....if my guess is right, it's nothing serious.
 

Karen Abse

Member
Joined
Jan 11, 2003
Location
Richmond, Virginia
TDI
Passat 1996 green
no modifications, I think...

I got the car well used from an auction so I don't know if there are any modifications. How can I tell?

No bio-disiel.

I was low on fuel with a couple of gallons in the tank. It's running a little rough and when I scooted out into traffic, it missed some.

Thanks.

Karen
 

Toronto_Vento

Top Post Dawg
Joined
Nov 7, 2002
Location
Richmond Hill, ON
TDI
01 Baltic Green Bora
Honestly, the only way to properly figure out what's going on is to have the car hooked up to a scan computer. Go here: http://www20.brinkster.com/beowulf9/tdi/vagcom/
and do a search for people with vag-com in your area. These people will often help you out for a cup of coffee, etc. I think you can also go to Autozone, and they'll scan the code for you. If you go to Autozone, you'll get a generic code, and someone here will be able to decipher it. If you go through someone on that link I provided, the computer will actually tell you what the code means.

Either way, come back here, and post the code you get by either method. After that, we may be able to let you know what happened, and what to do. If you go to Autozone, they won't clear the code for you, but if you go through someone from that link, they will. Just make sure you write down the code. I am guessing that once the code it cleared you won't see any more issues. (kind of one of those one-time things which happen)
 

Dave_D

Veteran Member
Joined
Jun 9, 2003
Location
Gaithersburg, MD, USA
TDI
2015 Passat Titanium Beige six speed manual & Jetta, 1999.5, Tornado Red
CEL & flashing GP

I had this happen on my TDI a few months ago when the connector to the start-of-injection needle lift sensor on the injector for cylinder 3 came loose. If you could have someone scan your car with a VAG-COM you would know if it is this or another critical sensor that is the problem. There may be other critical sensors that will cause this, but I would certainly check this one in particular. If that connection is good I would look for other loose connections in the engine compartment.
 

Lug_Nut

TDIClub Enthusiast, Pre-Forum Veteran Member
Joined
Jun 20, 1998
Location
Sterling, Massachusetts. USA
TDI
idi: 1988 Bolens DGT1700H, the other oil burner: 1967 Saab Sonett II two stroke
BK / GQ engine controller

Karen Abse said:
I got the car well used from an auction so I don't know if there are any modifications. How can I tell?
No bio-disiel.
I was low on fuel with a couple of gallons in the tank. It's running a little rough and when I scooted out into traffic, it missed some.
Thanks.
Karen
Your check engine light (CEL from now on) probably came on from the missfire. I suspect that the high output signal from the fuel injector pump during this acceleration attempt did not match the low engine rpm speed during this missfire and that this discrepancy created a notice of a fault. Air in the fuel lines will do this. The low fuel level may have contributed. Consider replacing the fuel filter and checking the integrity of the hose ends and the seal of the thermal valve on top of the filter.

The 1996 Passat came from the factory with an engine control unit (ECU, another acronym to remember). There was an updated version for the 96 ECU introduced during the 97 model year run. These two 96 ECUs are identified by the suffix after the part number. The original 96 ECU has a BK suffix. The newer 96 ECU has a GQ suffix. Knowing which ECU you have will assist in determining which modifications are benefitial and should be considered, and which are unnecessary or even detrimental.

The ECU is mounted under the hood in the area near the right windshield wiper. Lift up the black splash shield covering the cabin air filter and look under. The original BK is in a black plastic case, was built before compliance with the second generation of the industry standard On Board Diagnostics (OBD II) was required, but supports some diagnostics (under the prior OBD protocol) without additional code readers. The GQ is in a silver color cast metal case, is OBD II compliant and requires a code reader for all fault codes.

If the ECU in your Passat is a black plastic case BK version, a code can be read from the check engine light by following these steps:
1, Turn the ignition key to ON, but not to the START position.
2, Quickly press the accelerator pedal to the floor and quickly release it five times within five seconds.
3, Wait about 5 seconds.

A BK series ECU will begin to flash the yellow lamp in a four digit sequence. Counting the number of flashes will produce a code from 1111 to 4444. This code can be looked up in a table to determine the fault. A GQ series ECU will not flash the yellow lamp. This GQ ECU requires an OBD II reader for all faults.
 

TWSTDVW

Veteran Member
Joined
Oct 24, 2004
Location
Shaw District DC
TDI
2k Golf GlS
I also just got a glow plug light and CEL with a kinda rough start this morning. Car ran fine to work. I also just put a 5 gallon jug of Bio-D in last night. I will scan the codes during my lunch break.
 
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