How to Replace a Temperature Sensor MKIV VW/Audi, Jetta, Golf, 1.8T DIY
Fix Temp Sensor DIY
Recently my temperature sensor had gone out on me again, so I figure this time around I'll take some pictures and save everyone a couple hundred dollars from the dealership. Most of the original sensors placed in the MKIV cars were faulty and instead of a recall VW/Audi was nice enough to come out with a new revised part and let us pay for it. The revised part number is 059-919-501A and will have a green top as opposed to the original black or blue top that was in your car. No matter if you drive the A4, Jetta, Passat, Beetle or GTI this should be the correct replacement part, but always check with your local V-dub dealership. For some reason all the dealerships are charging a different amount for this part so expect to pay anywhere from $25-$40 for this fix. The part can also be bought at Autozone for $8.99 (part # SU5404), I have heard mixed results with using the autozone part but it does come with a two year warranty. Another option is to buy online to save some cash. I don't trust most online stores but one good one for OEM parts is ECS Tuning. Along with the sensor I would recommend buying a new O-ring and clip.
Once the bad sensor is replaced you should see an increase in gas mileage and it is also known to steady the idle as well as making your in dash gauge work properly again. And as always lets give the stealership a call and see how much they charge to do this 10 minute repair. The dealership quoted a price of $161+tax for the repair, parts being about $38. So savings on this DIY is about $120.
Symptoms of a Faulty Sensor
Some cars will receive a check engine light when the sensor goes bad and some will not. If you have an error code go down to your local auto store and have them scan it for free. If you are receiving any of these codes it is most likely your temp sensor.
- 17704 Error in mapped cooling system
- 01039 ECT Sensor
- p1296 35-00
Most of the time you will be able to tell that you have a bad sensor by the way your temperature gauge needle randomly floats around or stays at zero or a fourth of the way up when your car is fully warmed up. When my sensor first went out the needle on the temperature gauge just stuck on zero. I took the sensor out gave it a good scrub and it lasted about another half a year (don't be cheap like me, just buy a new one), but both times I did not receive a check engine light so I'm guessing that's just random.
If your temperature gauge is reading above 190 degrees more than likely it is not your temperature sensor but your thermostat or even worse your water pump. Ouch! that's gonna cost some money!
Tools & Part Numbers For the Job
This is a very easy fix only needing a flathead screwdriver and about twenty minutes of time.
- Sensor: 059-919-501-A or Autozone Part #SU5404
- O-Ring: N90-316-802
- Clip: 032-121-142
- A few sizes of flat head screwdrivers
WARNING WARNING WARNING
Coolant in your car after it has been running is extremely hot. So if you do not want to risk a 200 degree fahrenheit money shot right to your face then do not attempt to change this sensor until your car is completely cooled down.
I recommend the "better safe than sorry" method on this one and let your car cool down overnight, then do the repair in the morning. Seeing how the repair will only take most people about ten minutes (thirty at the very longest) this could even be done before you go to work. Another benefit of waiting till the car is bone cold is it will leak very little coolant while swapping out the sensor. If you want to attempt this DIY while your car is still hot use google to find instructions for that method and print yourself out the directions to your local burn victims unit just in case.
Lets Get This Party Started!
- Make sure your car is completely cooled down.
- Loosen your coolant reservoir cap to release any built up pressure, then tighten the cap back up. By doing this you create a vacuum seal so when you pull out the bad sensor very little to no coolant will leak out while you are making the swap.
- The temperature sensor is located directly to the right of your valve cover as you can see in the picture. If you have an Audi A4 or passat it is located between the firewall and valve cover in front of the battery enclosure. You can choose to remove your engine cover if you'd like but you should have enough room with out removing it. I can't say for sure because I have no idea what happened to my engine cover. To remove the cover push down on the screws and twist left (looking at it should be pretty self explanatory).
- Once you locate the sensor wedge your flathead screwdriver between the clip and your sensor. If you didn't want to go all out and buy the new 65 cent clip then be gentle so you don't warp or break it. Now pull out the sensor while it is still connected to the wire harness. Some coolant may leak out, if you are concerned you can place some paper towels under the hose before you remove the sensor.
- Release the wire harness by using your fingers or a small screwdriver. I talked about these little clips before in one of my other DIY's. Just use gentle pressure, no need to show off for the ladies and get all he-man here. The clips can be fragile so the last thing you want to do is break it. Update: I just broke one off, Here is a diy on how to replace broken harness connectors if you accidently break yours.
- Once your old sensor is released from the wire harness check to see if the o-ring is on it, If the o-ring is not on the sensor then dig it out of the hole with your little pinky finger. (Wow that brings back high school memories).
- Before you stick the new sensor in I like to lube up the new o-ring with a little coolant to help it all seal up properly.
- Slide your clip in gently, plug the wire harness back in and start up the car. As long as nothing is leaking out then you're good to go. If your coolant is low pour a little distilled water in the reservoir to top it off (do NOT mix it with store bought coolant).
If you do have a check engine light on you have two options now. You can unplug the negative terminal on your car battery for a few seconds which will reset your fault codes or can can just ignore the light for about sixty miles and as long as that was the only problem the light will turn off on its own.
Questions and comments: If you have any please feel free to leave them below.
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