cel - codes: P0671, P0673, P0674, P0128 - glow plug, coolant temp. driver's window does not work driver's controls do not operate any other windows driver's door lock does not engage others, sometimes unlocks with key fob found ONE unconnected connector by door switch. in door panel. driver's door release fuel door ok driver's door does NOT release tailgate suspect replacement door was a 2000, original 2003 speedo does not work http://www.taligentx.com/passat/maintenance/doorlockmechanism/ http://www.discounttire.com/dtcs/findTireDetail.do?c=1&rcz=98203&ar=65&rf=true&rd=15&rc=WASINT&cs=195&dVeh=dVeh&tc=BRIHHC&yr=2003&pc=25746&cf=false&vid=008199&sw=false http://forums.tdiclub.com/showthread.php?t=79819&highlight=glow+plug+replacement codes: P0671, P0673, P0674, P0128 related to P0128 http://forums.tdiclub.com/showthread.php?t=208410 coolant migration can cause it to come back. bad connections, bad grounds. Hi - The CEL in my car comes on daily (almost) and is always a code P0128. I replaced the coolant temp sensor and it is still throwing the code every day. Is there anything else that could cause this code? I would pull the connector to the plug and see if it's green, then I would pull the raintray cover and check the small connector to the ECU, see if that's green. otherwise start cleaning grounds. http://forums.tdiclub.com/showthread.php?t=79819&page=16 OK, I wish I would have read this earlier...so I wasted some $. However I still have problems. I have a Jetta 2003 TDI (ALH), my MIL and CEL light were coming on, so I purchased a OSDII reader from Harbor Freight for $49 (capable of resetting the codes, normally $79). The OSDII reads P0671, P0672, P0673 and P0674 (glow plugs right!). I tested the gp's and they were fine...but I already purchased replacements and put them in (and the new ones test fine). I replaced the gp harness (however I tested the old one and it tests fine...didn't cut it out of the system, just bypassed before I cut it out). I purchased electrical contact cleaner from AutoZone and hit the gp's, harness, relays, fuses, battery. No luck. After replacing all of these items my CEL light has gone out, but my MIL and my battery light are both on. I tested the battery and get 12.6v, so I am good there, however the battery cell light isn't green, dead black (but still test fine, with and without load). I inspected the fuses on the battery and they looked fine, but tested and get 12.5-12.6, so they seem fine. I have a friend with a Jetta 2002 TDI, so instead of testing the relay switch, I swapped them! Thought I was being smart. Anyway, still throwing P0671, P0672, P0673 and P0674, with MIL and Battery light on. I reset the codes and they come back within 30 sec of starting the car and the battery light is on all the time. Also, Tail-lights are functioning fine (aftermarket APC). Read some posts stating the tail-light throws the CEL. Don't know if any of this is related, but at the same time, my AC doesn't seem to be functioning anymore (doesn't engadge at all--haven't tried rpm above 3,000). I am lost and don't know where to turn. both dealerships around me are idiots and I am new to the area, so don't have anyone to refer me to a good Diesel mechanic. Thanks in advance for any help... jaywv0489 is offline Reply With Quote snipped the post to save space. I did all that was suggested in this thread. New harness Check glow plug reistance Checked for power at each glow plug boot Removed glow plug and applied power, glows within a second. My 2001 (2002 titled) TDI Beetle, auto trans starts and runs ok. But I still have a check engine light. The glow plug light is red for about 2 seconds, then turns blue. Is there a code reset I need to do? john jacob [quote=Wingnut]Well, its been over a year since my original glow plugs 101 thread. I just got the code back so I had to do the testing procedure again and thought I would redo my How to with new pics & info. So here goes. The glow plug codes are a popular code to be thrown on our cars. Several versions of the DTC are 16764 / P0380 code (Glow plug/heater circuit electrical fault (Q6)) 17055 / P0671 code (Cylinder 1 Glow plug circuit (Q10)) 17056 / P0672 code (Cylinder 2 Glow plug circuit (Q11)) 17057 / P0673 code (Cylinder 3 Glow plug circuit (Q12)) 17058 / P0674 code (Cylinder 4 Glow plug circuit (Q13)) The first code is for 2001 and older cars. They have a 2 wire glow plug harness, so just throw a generic code for the glow plugs.