Faulty exhaust temperature sensor

[OldMan52]

Car: 2009 Jetta TDI - 85 000 miles
9 Months ago, had the exhaust flap replaced. Three weeks ago, the check engine light went on, then off, and on again. Not a glow plug issue because car starts easily. Last week, got a blinking glow plug signal for a short while, then no more. Check engine light goes on during the day, but when I start the car in the morning, usually the CEL is off. Went to the VW dealer to check the fault code. Apparently, the first exhaust temperature sensor is out of range, and this is what triggers the check engine signal. Their diagnostic: 1st sensor 150C (approx 300 F), the other three exhaust sensors in the low 200F range - the temperature difference is what triggers the CEL. Their recommendation: replace the 1st sensor. Estimate: 6 hours labor ( not easy to work in that area) - cost about $900 (sensor costs $300). VW might participate in the repair. My problem is that I'm not really sure the first sensor is not reading properly and that it needs to be replaced. The first sensor is before the DPF, and maybe flow restriction is causing the difference in temperature with the other sensors. The dealer kept the report to discuss with VW so I don't remember the fault codes. I am driving to Florida in one week, and don't think I will do any repair before I come back. If anyone has ideas, please help.

 

[DZL_Damon]

I'm unfamiliar with other manufacturer's stock exhaust temperature sensors, but VW uses an open type EGT probe that has an exposed element protected by a cage. All the systems I've ever installed on trucks, or used in industrial applications are fully enclosed and do not look as vulnerable.

The reason VW uses this style EGT probe is for very fast response to reading changing temperatures.

With all that said, I have replaced my first temperature sensor (pre turbocharger) that failed on my car at 56k. Looking at the probe when it was out, I could see the sensor inside it's cage broken off, however mine was reading a high temperature, not low. It did give sporadic alarms and Check Engine Lights before it stayed on permenantly.

Sadly, this replacement DOES necessitate removing your DPF. You CAN do it with some a few tools beyond a normal tool set such as Torx head wrenches, Allen keys, triple square drivers (looks like an inverted 12 pt socket) and some rachets with extensions and universals are always great. You can get your triple square kit (used ALL over the VW) from Metalnerd sold at IDParts.com. There has been enough of these failing that IDParts.com now sells the sensor for about $130 I think. I bought mine before they had them for about $160 from Jim Ellis VW who sells VW parts online.

This is the sensor removed, you can see the "Cage" I mentioned:

This is looking into the inlet of the DPF and looking at the 2nd EGT probe (Pre DPF probe or Post turbo probe) You can see how far it sticks into the exhaust stream.

Here is the sensor when it finally failed on VCDS while the car was cold:

Here are all 4 connectors for the EGT probes, behind the battery. I think I removed a little cover to see them. 3 are on the front, and I think the one for pre turbo is on the back of the little mount they are arranged on. I think the pre turbo connection is black (They are all 4 different colors so you don't mix them up). You can swap one of them (might have to snip a little tab of plastic so they will swap). If the temperatures switch on VCDS, you know the problem is between the sensor and it's connection and not from the connector to the ECU. My battery cover is up to keep the trickle charger on in this photo:

Oh, you do NOT have to remove your subframe to get it out, but you do have to massage the insulation and tin work above the subframe to wiggle the DPF out. I was able to use the palm of my hand and push it up to gain another 1/2"-1" clearance. Remove all sensors before trying to wiggle it out.

You will also have to remove 1 axle shaft. This is a good opportunity to get an aftermarket downpipe and a tune from a tuner of your choice. I would recommend Mr. Mark Malone based on amazing personal customer service that he showed me when I had an issue. He went above and beyond to make sure I was satisfied, and I believe a business ethic like that should be advertised and praised.

 

[OldMan52]

I could see the sensor inside it's cage broken off, however mine was reading a high temperature, not low. It did give sporadic alarms and Check Engine Lights before it stayed on permenantly.

In fact the sensor is giving a reading that is too high, same as yours. When it's below freezing, CEL turns off at start-up. Otherwise, it stays on.

Great write-up DZL_Damon! Now I understand better. I'll wat to see if VW will share the bill. Otherwise I will send the car to a trusted mechanics who works at much lower rates.
THANKS!

 

[mlgjr]

Hello. I am very interested in this thread. My 09 tdi has the CEL on and the blinking glow plug light. I took it to two separate shops and both got the P0544 code. I have read several threads on this topic and it looks like it is the black connector sensor that is the tough one to reach. I purchased the car with 68k miles on it (it now has 80k miles) and I don't have a warranty. I am a seasoned mechanic with sbc engines....but this tdi engine is completely new to me. I am trying to learn more to see if this is a job I want to farm out or bite the bullet and have a shop do it. I just purchased the sensor on Ebay last night. There was a VW parts place selling it for $108.00. Other places wanted $130+ without shipping. I looked on You Tube for any videos that might exist on this install...but have found nothing. Thanks for any advice folks can give......

BTW....I commute over 130 miles a day and I love this car. Perfect blend of power and mpg. I also own a 2011 tdi jetta. Bought this one new.

 

[OldMan52]

Sorry to learn you have the same problem. I haven't had the time to look into it further cause I was driving to Florida for the Christmas holidays. Before leaving, I really blew the **** out of this car, driving it at 80 mph going up a steep hill in 6th gear. Boy are these Tdi powerfull! The heat probably burnt much of the soot around the sensor. Anyways, I used the trick MartelArtiflex gave to clear the fault code in a prior thread and cleared the CEL and blinking GP warnings. Before leaving for Fl, I drove 300miles without any warnings. GP light came on again after 600 miles, cleared the codes, and drove the rest of the route to Miami. I still get an occasional warning, but they are easy to clear, and I go a long way before a CEL comes back again. Hope to get back to Canada without any issues. I still think I will need to replace the sensor, but for now, I can still live with this annoyance. I will advise when I get back

 

[OldMan52]

Worries only

My 09 tdi has the CEL on and the blinking glow plug light. I took it to two separate shops and both got the P0544 code. I have read several threads on this topic and it looks like it is the black connector sensor that is the tough one to reach.

This is exactly what I'm going thru right now: blinking glow plug light, Check engine light. Dealer says Temperature sensors just past the motors needs to be replaced. $900 estimate. Now the dealer says he will give me a $300 credit.
I've still haven't decided to replace the sensor. I've driven from Canada to Florida - 3600 miles with no issues except warning lights. When returning from Miami, NEW WARNING: DPF light went on. Panic, I feared I would not make it to Canada so I dropped off at the VW dealer in West Palm Beach. Diagnostic: temperature sensor, all systems OK, DPF light should turn off while driving - no need to worry. I drove 1800 miles with the DPF light on.
When close to home, I decided to push the car to its limits to get rid of the DPF light. In 6th gear, rev at 2200 RPM, then push the accelerator and let go slightly - see if the car picks up in speed, push further and let go, accelerate up to 90 mph, maintain for a minute or 2, then let go and return to driving speed (I didn't want to get a ticket). Did this 3 or 4 times. DPF light turned off. Reset the blinking GP and CEL - NO MORE ALARMS since 2 days.

CAN SOMEONE TELL ME WHAT'S GOING ON??? If the temp sensor is defective, I should still be getting Blinking GP. Local dealer says I still need to replace the temp sensor, that the car computer is disregarding the temp sensor because 1 in 4 temp sensors is out of range.

 

[Efchou]

@OldMan52
I had this issue, when you lose an EGT sensor, the ECU sometimes throws the car into a lower power mode. At least mine did anyway. Have you noticed a loss of power? When you drive the car without its sensors operating fully, especially in a limp mode, the DPF will start to get loaded down with soot. I believe (not sure on this one) that the ECU won't do a regen unless the 3 sensors are operating properly. Also, driving the car gingerly all the time is not good for turbo and DPF components as the fuel is not fully heating up and EGT's aren't getting high enough, thus pumping more soot into these components. That's why a regen is usually initiated during a higher RPM. As for sensor replacement check the wiring harness too, I remember my EGT sensor no. 2 was always reading out of range whenever it got hot due to some faulty wiring harness.

 

[OldMan52]

@OldMan52
Have you noticed a loss of power?

The car sputtered at low RPM, but at 2200 and over, ran fine.

@OldMan52 the ECU won't do a regen unless the 3 sensors are operating properly. Also, driving the car gingerly all the time is not good for turbo and DPF components as the fuel is not fully heating up and EGT's aren't getting high enough, thus pumping more soot into these components.

Thanks for your input Efchou. You are probably right. The thing is nobody seems to know for sure. Right now, all warning lights are off, and the car no longer sputters and has plenty of power. I think that driving the engine at high rpm with a good load clears the exhaust and DPF as long as you don't give excess fuel.
My old 2001 Beetle didn't have a DPF, and I could see thru the rear view mirror what conditions generated smoke. Constant high rpm never gave smoke. Smoke comes from too much fuel for the motor rpm.
The problem with the 2009 Jetta is the 6th gear. Older TDI (5 gears) ran 2200 rpm at 60 mph. The 2009 runs 1800 to 1900 in 6th gear, which is too low considering the weight of the car, especially if you have inclines. I've changed my driving style and now, I use the 6th gear only passed 65mph.
I will wait another week or 2, and if the warning lights come on again, I will have the local VW dealer replace the temp sensor 1st (pre-DPF) temp sensor. If you have any comments, please feel free to respond. I appreciate your help

 

[DZL_Damon]

Change the sensor.

People have reported DPF clog failures with less mileage than you put on.

Your sensor needs to be changed based on the info given. Untill you get a VCDS scan and do some troubleshooting to prove otherwise: you need to change the sensor.

 

[OldMan52]

Change the sensor.

People have reported DPF clog failures with less mileage than you put on.

In the city where I live, 2009 + TDI's are very common. The VW dealer has never replaced a TP sensor (G235) before on Jettas or Golfs (TDI Toureg only, because of the urea system). Nor has the largest import car service center. And since 1 week, no more signs of defect what's so ever. That's why I am delaying a bit. The warnings will certainly come back and I will have the TP sensor replaced. Thanks again

 

[DZL_Damon]

Yeah, mine flashed in and out for a few weeks before it went flat. Sometimes I would start and have a code, then it wouldn't. VCDS monitoring would have it act normal, then flash erratic, then normal. Then steady 900+*F one day. Found the inside of the sensor cracked.

It's not a super common issue, but it's common enough that IDParts.com started carrying that exhaust sensor, and only that one. This one sees the highest temperature and pressure with the most fluctuations vs all the other ones.

Keep an eye on things, that's all I'm saying.

 

[OldMan52]

My repair is scheduled for next Tuesday. We'll see how much it costs.

 

[OldMan52]

Close call for the dpf filter

My repair is scheduled for next Tuesday. We'll see how much it costs.

- Got the G235 temperature sensor repaired January 22.
- Three days before my scheduled repair, the DPF light went on again. I tried to kick it off driving 3000 rpm for a couple of hours without any luck.
- Went for my repair. Dealer replaced the sensor. However the scan gave a warning saying NOT TO REGENERATE because of risk of fire. ALSO SAID DPF NEEDED TO BE REPLACED.
- the service man went out with the car, drove about half an hour at 3500 rpm and controlled the dampers and regenerated the DPF. See documents 130122 pg1, pg2 and pg3 I posted in the photos section. KEY WORD - DPF WARNING.
I have also posted the diagnostic report performed December 12.
What I've learned from this is that THE G235 SENSOR IS EXTREMELY IMPORTANT, even if you drive only highway, and you can clog your DPF if the G235 doesn't measure properly.

COST OF THE REPAIRS (before taxes): $848.08
- PARTS: $468.22 TOTAL - GASKET $6.91; 2 COLLARS $50 EA; $6.31 SEAL; TP SENSOR $355
- LABOR: $379.86 ; LABOR FOR REPLACING THE G235 SENSOR: $300.30; LABOR FOR UNCLOGGING THE DPF: $79.56
THE DEALER PAID 35% of the cost (excluding DPF unclogging). I paid $578.90
I would have paid $499 if the dpf had not been clogged.

If anyone has comments, let me know.

 

[DZL_Damon]

... results as foreshadowed

 

[BigBadSubaru]

Did mine this weekend

Did my pre-turbo sensor today, thought I'd add to the pics, first pic shows where the sensor is (the tip of my "eyeball snatcher" hook tool is pointing right at it, second pic is how I got it out, 17mm Harbor Freight crow's foot wrench and a short locking extension. Used a passenger side mirror off a Prius to see what I was doing. (I used to work for Toyota, people like to back into stuff and snap off the passenger side housing, and the mirror glass comes in handy)

http://imgur.com/a/1785j