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    Thread: Emissions Inspection DTC Codes P1296 P0420

    1. 02-24-2010 06:15 PM #1
      My first post. I found the VWVortex doing Google searches and it seems like the best collection of information for my "new" vehicle. I'm looking forward to all the good help available.

      2001 VW Jetta 2.0L 4-cyl AVH, 100 050 miles

      Part I:
      Failed Georgia Emissions Inspection with following codes:
      DTC1 = P1296 - Manufacturer specific code.
      DTC2 = P0420 - Catalyst Sys Efficiency Below Threshold (Bank 1)
      DTC3 = P1296 - Manufacturer specific code.
      *Technician also informed me that the test would have failed automatically since the CEL (MIL?) is on. Mileage at time of test was 99710.

      Part II:
      I took the car into my local dealership. They did a diagnosis for $50 and then quoted $500 for repairs. As much as I need to pass my emissions inspection, $500 is money we don't have right now so I declined service.

      Part III:
      I searched the archives for P0420 and P1296 and read every single thread in the IV forum. 2 hours later I feel much smarter but I still don't feel like I'm smart enough to attack this DIY. Need tips.

      Part IV:
      Here's what I learned (any comments & corrections would be really helpful):
      P1296 - Most replies indicate that this is either a bad Engine Coolant Temperature (ECT) sensor -OR- a bad thermostat. Engine appears to already have a "Green-Top" but I bought a new one ($13) and intend on installing myself. Even with CEL on (~2 months), vehicle runs smoothly. I have not noted any problems with vehicle temperature. I'm not sure why the code P1296 appeared twice on the EI report.

      P0420 - Most replies indicate that this is either a bad cat -OR- bad O2 sensors. I have also seen remarks about MAF and O2 sensor spacers. I checked prices for the O2 sensors at NAPA today and they were about $120 each (ouch). I've also learned about a 10-year, 120k cat warranty that applies only for the AEG and possibly a 10-year, 100k warranty appies for the AVH. Found the links on the EPA.gov web site. I'm currently at 100,050. When I asked a 2nd dealership about running a reflash or checking the VIN or checking the warranty all they said was "We can't really tell anything until you bring it in and we run a diagnosis. Even if it is the cat... and even if it is under warranty... we won't provide a cat replacement at no cost until we determine that everything else with the car is correct."

      Part V:
      I'm at the point where I want to attempt this myself and try to save as much money as possible. My general engine knowledge is pretty poor... but my DIY skills are decent. Any tips?

      *Here in Georgia, we can get an emissions re-test for free at same location as original (within 30 days). There is a "Owner Self-Repair" section to be filled out. I need as many tips as possible about which engine components to start replacing. And then, after I make repairs, how long do I have to drive it to clear codes?


      Modified by mnshewch at 3:55 PM 2-24-2010


      Modified by mnshewch at 3:59 PM 2-24-2010


    2. Senior Member bluefox280's Avatar
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      02-24-2010 06:59 PM #2
      Quote, originally posted by mnshewch »
      P1296 - Most replies indicate that this is either a bad Engine Coolant Temperature (ECT) sensor -OR- a bad thermostat. Engine appears to already have a "Green-Top" but I bought a new one ($13) and intend on installing myself.

      Do that first; replace the CTS, clear out the fault codes with a VAG-COM.

      Quote, originally posted by mnshewch »
      I'm not sure why the code P1296 appeared twice on the EI report.

      Because the ECU has spotted the problem two individual times.
      Unlike the MK5, there's no time / date stamp associated with when the fault was triggered.

      Quote, originally posted by mnshewch »
      P0420 - Most replies indicate that this is either a bad cat -OR- bad O2 sensors. I have also seen remarks about MAF and O2 sensor spacers.

      Again, both the O2 sensors can be checked with a VAG-COM.
      Data-logging the measuring blocks of the O2 sensor voltage during RPM's and load will tell you alot.

      Quote, originally posted by mnshewch »
      I'm at the point where I want to attempt this myself and try to save as much money as possible. My general engine knowledge is pretty poor... but my DIY skills are decent. Any tips?

      Get hold of a local owner with a VAG-COM to help you properly test, diagnosis and isolate your catalyst efficency problem.

      Also, how did you fail you emissions? Do you have burn part-per-million (PPM) readings?
      How was your CO, CO2, NOx, HC and burn readings?

      Quote, originally posted by mnshewch »
      *Here in Georgia, we can get an emissions re-test for free at same location as original (within 30 days).

      Same with Colorado; I just went through a catalyst replacement after failing twice on a bad cat... there are tall-tail warning signs.

      Quote, originally posted by mnshewch »
      And then, after I make repairs, how long do I have to drive it to clear codes?

      "Readiness" of the ECU takes a handful of cold- and warm-starts.
      You can override and set readiness instantly with a VAG-COM to confirm if repairs are good.

      - Erik

      Pattern Draft Imaging.com - "...Where Engineering Discipline and Photography Merge as One..."

    3. Member scirockalot8v's Avatar
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      02-24-2010 07:43 PM #3
      bluefox280 for president!

    4. Moderator DannyLo's Avatar
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      02-24-2010 08:21 PM #4
      for the po420, an easy way to check if catalytic converter is functioning properly is to get a temp gun and shine it pre, and after the cat (RIGHT at the welds). Afterwards the tempurature should be around 20% hotter than pre-cat to indicate it is catalyzing properly. If its anything else it's almost always the cat.

    5. 02-25-2010 02:42 PM #5
      Wow, lots of good information. Thanks!

      I drove the Jetta over to a local AutoZone today and they hooked up some gizmo under the dash to check codes. I'm assuming this was a VAG-COM (maybe not). The tech printed out the following info for me.

      P1296
      Definition: Cooling System Malfunction
      Explanation: Check Coolant Level
      Probable Cause: 1. Check CTS and circuit

      P0420
      Definition: Catalyst system efficiency below threshold bank 1
      Explanation: Faulty Catalytic Converter
      Probable Cause: 1. Rich Air/Fuel ratio, 2. Air leak near rear H02S, 3. Faulty fuel control H02S (Heated oxygen sensor).

      I'm a little confused on the info. For both codes, the "explanation" seems to refer to a completely different item than the "probable cause". I guess it doesn't matter - I intend on doing the repairs in order from cheapest to more expensive.

      Regarding the O2 sensors - the tech said he thought that Bank 1 meant upstream (before cat?). I feel like most of the archived threads that I have read suggested the more likely location for the faulty 02 sensor would be downstream (after cat?). And the print-out refers to "rear" H02S. He also recommended doing a fuel injection to clean things out. His english wasn't the best. I have no idea if his suggestions are good ones or not.

      Follow-up questions:
      1. Is it possible that what the device he hooked up is different than a VAG-COM?
      2. Should I start my P0420 repair by buying an 02 Sensor (he printed up a price for a Bosch Part #16121 as $83.99)? [The quote for the catalystic converter was $460.99... if it is actually the cat than I might as well take it back to the dealership that quoted $500 for repairs].

      P1296 seems easy enough to attack at this point.
      But I can understand now how so many people hate the P0420.

      ps. Thanks again bluefox! The printed emissions reports in GA do not show anything about PPM or specific gases... just fault codes.


      Modified by mnshewch at 11:50 AM 2-25-2010


    6. Senior Member bluefox280's Avatar
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      02-25-2010 02:52 PM #6
      Quote, originally posted by mnshewch »
      I drove the Jetta over to a local AutoZone today and they hooked up some gizmo under the dash to check codes. I'm assuming this was a VAG-COM (maybe not).

      No that's just a generic OBD-II scanner, not an authentic VAG-COM: http://www.ross-tech.com

      Quote, originally posted by mnshewch »
      Regarding the O2 sensors - the tech said he thought that Bank 1 meant upstream (before cat?).

      No. If it was pre-cat it would refer to Sensor 1; post-cat is Sensor 2.
      Bank refers to the left or right exhaust downstream on a split v-orientated engine (like a V4, V6, V8).
      Bank one is left-side, Bank two is right side.
      However with only one exhaust downstream pipe, you only have Bank 1 (which isn't side dependant at all).

      Quote, originally posted by mnshewch »
      And the print-out refers to "rear" H02S. He also recommended doing a fuel injection to clean things out. His english wasn't the best. I have no idea if his suggestions are good ones or not.

      There's not appearent reason why you would need a "fuel system" cleaner.
      That's just hog-wash; don't do it... fuel trim or poor combustion isn't your issue at hand.

      Quote, originally posted by mnshewch »
      1. Is it possible that what the device he hooked up is different than a VAG-COM?

      Oh yes; it's definitely not a VAG-COM; after checking Ross-Tech's site, you'll see why.

      Quote, originally posted by mnshewch »
      2. Should I start my P0420 repair by buying an 02 Sensor (he printed up a price for a Bosch Part #16121 as $83.99)? [The quote for the catalystic converter was $460.99... if it is actually the cat than I might as well take it back to the dealership that quoted $500 for repairs].

      No; you shouldn't spend a dime till you're able to confirm / deny the O2 sensor is working properly or not.
      Have you searched for CARB and OBD-II complient catalysts on the internet?
      They're cheaper replacements that will do the job.

      Quote, originally posted by mnshewch »
      ps. Thanks again bluefox! The printed emissions reports in GA do not show anything about PPM or specific gases... just fault codes.

      Nothing? Not to tell you what you failed on? Just other than you failed only?
      Does GA do an auto-fail due to a Check Engine Light (CEL)? Colorado does not.

      - Erik


      Modified by bluefox280 at 12:54 PM 2-25-2010

      Pattern Draft Imaging.com - "...Where Engineering Discipline and Photography Merge as One..."

    7. 02-26-2010 04:28 PM #7
      Thanks for the follow-up.

      I emailed all my local contacts (2 hockey teams worth of guys) and nobody owns a VAG-COM. One friend recommended a local repair shop and I scheduled an appointment to go in and get another diagnostic. I asked the tech at the shop if he had a VAG-COM. He said he didn't know what that meant. Eventually after trying to describe the VAG-COM he said "well yeah, we have a laptop with a bunch of software that we plug in and run". I guess this is the best I can get for now. Tuesday I'll have him run it and see what info he discovers.

      I only have a 15minute drive to work and temps have been about 30s, 40s here in Georgia lately. My dashboard temperature gauge doesn't move from 0. Does this tell me anything? I think I recall reading that thermostat shouldn't be a problem if my heat is working - which it does.

      On a side note, I run out of my 30 grace days on my original emissions inspection on Sunday. I can probably install the temp sensor on Saturday - and maybe that fixes the P1296... but I'm guessing there is nothing a NOOB like me can do to fix the P0420 in the next day or two. Time & money are both short these days with my 1st kid (6months).


    8. Senior Member bluefox280's Avatar
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      02-26-2010 05:35 PM #8
      Quote, originally posted by mnshewch »
      My dashboard temperature gauge doesn't move from 0. Does this tell me anything? I think I recall reading that thermostat shouldn't be a problem if my heat is working - which it does.

      That's a clear indication a CTS is faulty; especially when you're getting heat from the heater core.

      - Erik

      Pattern Draft Imaging.com - "...Where Engineering Discipline and Photography Merge as One..."

    9. 02-26-2010 06:18 PM #9
      CTS is definitely bad, I would also consider replacing the thermostat. When the computer does not get the correct temperature readings it will throw fault codes, because the CTS reads it is too cold out so adds more fuel, causing the code for the O2 sensors. Same scenario with the thermostat:

      If the thermostat does not open quick enough, the CTS reads coolant temps it does not like, therefore getting all pissy. I experienced this with my car as well as I would say this is the number one problem I have seen for other people with the Coolant Performance Code. However, since your gauge does not move, I would start with a temp. sensor (green).


    10. 02-27-2010 02:07 PM #10
      Thanks fox,fitz.
      I replaced the CTS today. Pretty simple - it is nice to feel like I made an improvement. I tried to set up a pan to catch the coolant, but the engine was a bit dirty and there was some dirt in the coolant. I decided to just add new coolant.

      Gave it a test drive, 30min, 20miles. Ran as well as previously - but at least the temp gauge increased and steadied at about 1/4 (two ticks before 190°, a couple times reached one tick before 190°).

      I contacted a VWvortex member with a VAG-COM in Atlanta. Really friendly. Offered to run a scan for me - but my wife's plans trumped the timing. Oh well. At least I got something done today.


    11. 03-08-2010 03:12 PM #11
      Hopefully these faults will be fixed soon.

      I met a VWVortex member in my area last Thursday. He gave my Jetta a VAG-COM run (at no cost, cool) and reset faults. I drove it home with no CEL light, but it came on the next day.

      Today I took the Jetta in to a PEP BOYS and had them run the OBD. The tech said it had the P0420 but nothing else. At least it appears that installing the $13 CTS fixed the two P1296 codes.

      Tech said that " this car is notorious for problems with the oxygen sensors". He asked me if I knew what that cost. I said "about $100". He said "Yeah... for the part... but labor is about $300... I don't know why". I thanked him and said I was going to try and figure it out myself.

      Questions (for anybody that reads):
      1. Next step: Another VAG-COM run to verify the problem is indeed an O2 Sensor?

      2. How difficult is an O2 sensor swap for a Noobie like myself?

      Note: Just found this link. Could it be covered by a recall:
      http://www.epa.gov/otaq/cert/recall/420b02003.pdf


      Modified by mnshewch at 12:53 PM 3-8-2010


    12. Senior Member bluefox280's Avatar
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      03-09-2010 02:39 PM #12
      Quote, originally posted by mnshewch »
      Tech said that " this car is notorious for problems with the oxygen sensors".

      False.
      After having my MK3 and MK4 for over driving 90K on each, the OEM Bosch sensors are not a common failure point.

      Quote, originally posted by mnshewch »
      Questions (for anybody that reads):
      1. Next step: Another VAG-COM run to verify the problem is indeed an O2 Sensor?

      Sure thing; voltage readings during normal operating temps will prove or disprove the claim.

      Quote, originally posted by mnshewch »
      2. How difficult is an O2 sensor swap for a Noobie like myself?

      Easy; jack / suppor the right side of the car, head under, and unscrew from exhaust.
      Some pentrating oil may be needed; and a O2 socket (easier that adjustable wrench) will be able to break it loose.
      From there, it's just wiring connections (grab an OEM unit with proper connectors) and you're back to it.

      - Erik

      Pattern Draft Imaging.com - "...Where Engineering Discipline and Photography Merge as One..."

    13. 03-09-2010 04:58 PM #13
      I too, am failing my emissions test due to P0420, and I stopped by Advanced Auto today to have the guy turn off my code (I have a scanner at home but I was on the road) and asked him if he thought I'd be able to pass. He said to drive for 30-40 miles, on main roads and highway so the car runs through several codes. After that, he said I should probably be good. Unfortunately, I was only able to drive for 5 miles on the main road when I called the testing center to see when they could squeeze me in. They told me to come in right then, so I figured I would give it a shot. And, as expected, I failed.

      Any thoughts as to whether the guy at Advanced Auto was right? Cause I certainly don't have the funds right now to buy a new cat, but if what he said is true, I'd definitely prefer to do that and hopefully mnshewch can do the same!


    14. Senior Member bluefox280's Avatar
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      03-09-2010 06:43 PM #14
      Quote, originally posted by tywall3 »
      Any thoughts as to whether the guy at Advanced Auto was right?

      Or wrong?
      If the catalyst is truly shot, a "ECU clear out" of fault codes isn't going to 'fix' the catalyst.

      The "readiness" is set by the ECU after a couple of both warm- and cold-starts.
      But if the emissions / inspections location pulls into the OBDII serial port, it doesn't matter.

      Do you have blow-results of what your shooting out? Like CO, NOx, HC's, CO2, and other compounds measured in parts per million (PPM)?

      - Erik

      Pattern Draft Imaging.com - "...Where Engineering Discipline and Photography Merge as One..."

    15. 03-09-2010 09:14 PM #15
      Unfortunately I do not have the results of what is shooting out. My emissions results page from today isn't really clear on what failed. It read:

      Overall OBD results: Fail
      MIL Engine off: Pass
      Readiness Results: Fail
      Misfire: REady
      Secondary Air System: Not ready
      Oxygen Sensor Heater: REady
      Connector Voltage: 13
      Catalyst DTC: No

      Everything else after pretty much says "Not Ready"

      On a side note (which I hope may fix the problem) I"m going to the dealership tomorrow to take care of a recall I got back in May 07.

      Basically I went down to the dealership when I got the letter in the mail, and at the time they told me that the recall was called off because they weren't sure what was going on. They said another letter would be sent out, but I never recieved one and only recently remembered that I still had the letter and thought maybe it would deal with this issue.

      The letter was concerning the ECM software for the cat monitoring system being to sensitive.

      Any thoughts?
      (Sorry If I"m unclear at any points, its all pretty confusing to me)
      Thanks for helping us out!


    16. Senior Member bluefox280's Avatar
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      03-09-2010 10:53 PM #16
      Quote, originally posted by tywall3 »
      Everything else after pretty much says "Not Ready"

      That's because you cleared out the DTC's and went directly to the emissions testing.
      The ECU's readiness ( http://www.ross-tech.com/vag-c....html ) was removed and that gave you the preliminary failure.

      Quote, originally posted by tywall3 »
      The letter was concerning the ECM software for the cat monitoring system being to sensitive.

      This is for your VR6? That's been a common ECU flash update.
      However, that doesn't tell you if the catalyst is still in good working order or not.
      If you have the burn results, that would GREATLY be of good diagnosis.

      - ERik

      Pattern Draft Imaging.com - "...Where Engineering Discipline and Photography Merge as One..."

    17. Junior Member 2002VWPASSAT1.8T's Avatar
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      03-21-2010 08:02 PM #17
      i'm having the same codes except i have a 3rd one which is p0688 "ECM/PCM Power Relay Sense Circuit Open". Could you pls tell me how you solved your p0420?? Don't know which O2sensor to buy is is 1 or 2?? And for your p1296 do i just need to replace my CTS?? PLS HELP ME.

      BTW. my CEL isnt on but my EPC light is.

      -MICHELLE-

    18. 03-29-2010 02:55 PM #18
      A final post to close my topic.
      I passed my emissions inspection today!
      I'm effin ecstatic.

      So happy the VWVortex exists.
      Without it, I would have shelled out $1600 for repairs.

      A quick summary:
      P1296: The dealership and another mechanic both quoted $500 to address this issue. They both listed t-stat, enging coolant temp sensor (ECT/ CTS), and wiring as items. Based on recommendations on the forum, I bought a $13 sensor and installed it myself. P1296 fixed.

      P0420: To be honest, I never did pin-point the fault. Mechanic quoted $1100 to replace the cat. Refused to pay it. That's money for diapers and formula that we need these days. I jacked the car up last weekend and disconnected the post-cat O2 sensor. What a PITA getting it loose!!! Took it out, cleaned it up, and... put it back together. A friend cleared my faults out with his OBD and I've now driven 72 miles & about 10 hot-cold starts since. No CEL. No P0420.

      Happy, happy, happy me.

      Thanks to everybody who helped and others whose topics helped me solve this b!tch. Time for s


      Modified by mnshewch at 12:03 PM 3-29-2010


    19. Member realcyberbob's Avatar
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      04-26-2010 03:02 PM #19
      How did you clean your 02 sensor? Is the code still gone?

    20. 05-21-2010 01:22 AM #20
      I just caught this thread. I am having the same P0420 code in my 2002 Jetta Wagon 2.0L. I had the code first appear last year and the dealer replace my cat free of charge under warranty. Now the code is back. This happened shortly after one instance of engine misfire. I know that a misfiring engine can kill a cat, but this car misfired literally no more than 3 times before I had new plugs, wires and an ignition coil so I can't imagine it killed the cat that quickly. I replaced the rear O2 sensor and the code stayed away for about a week and then returned. I have a green top CTS that seems to be working fine, I have cleaned the MAF, new air filter, no intake leaks that I can find, no exhaust leaks that I can see/hear, no other DTC's and no performance issues. The only thing left to suspect is the pre-cat O2 sensor. I have a Vag-Com and have made voltage readings on my O2 sensors but I am unsure of how to interpret them. I have ran the O2 sensor tests in basic settings and they both pass OK. The cat test in measuring block 046 sometimes passes and sometimes fails. The rear O2 sensor is an OEM VW part from 1stvwparst.com and the entire car is stock.

      While driving at a steady RPM, the front O2 sensor reads a steady 1.5V and the rear O2 sensor reads between .450V and .600V. From what I understand this is normal and indicates a Lambda value of 1 and a correct A/F mixture. When I accelerate (4000-5000 RPM) the rear sensor voltage rises to around .700V or sometimes .800V and drops to 0V when decelerating. At the same time, the front O2 sensor stays around 1.5V during heavy acceleration and rises to 4V while decelerating. From what I understand this is all normal except that the front O2 sensor is supposed to drop to under 1V (.2V-.3V) while the engine is under heavy load. Is that correct? If so, how can I tell if it is a stuck O2 sensor or an improper fuel ratio using Vag-Com?

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