Output Speed Sensor Circuit

Tiny
SPINOU
  • MEMBER
  • 2006 VOLKSWAGEN JETTA
  • 2.5L
  • 2WD
  • AUTOMATIC
  • 125,000 MILES
I had my car scanned with three different mechanics since the check engine light is on and they all said that is because of the output speed sensor circuit which is located inside the transmission. I purchased a new one from a Volkswagen dealer and had it replaced at one of these mechanics, but at the end, the check engine light is always on and it is still showing the same issue when scanning (Output Speed Sensor Circuit). The transmission is shifting even worse now. Any idea of what is causing this?
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Friday, August 12th, 2016 AT 9:30 PM

7 Replies

Tiny
CARADIODOC
  • EXPERT
You purchased a new what? Did anyone diagnose the cause of the problem?
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Friday, August 12th, 2016 AT 9:39 PM
Tiny
SPINOU
  • MEMBER
I purchased a new output speed sensor circuit and had it replaced, but it is still showing the same issue on the "scanner device" I still have not diagnosed the car. The mechanic guy said that the problem might come from the wires or the computer, but he is not 100% positive.
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Friday, August 12th, 2016 AT 11:32 PM
Tiny
CARADIODOC
  • EXPERT
There is a misunderstanding. You do not purchase an entire circuit; you diagnose it. I suspect you purchased a speed sensor. This is a real common mistake, and your mechanic is right. In fact, I do not read that very often. What he is referring to is diagnostic fault codes never say to replace a part or that one is bad. They only indicate the circuit or system that needs further diagnosis, or the unacceptable operating condition. First we have to inspect the wiring for breaks or grounded wires, and the connector terminals to see if one is corroded or stretched. Next, voltage readings will help to identify a wiring problem, but that is much easier when you have a scanner to view live data. When you pop in a new part that is referenced in a fault code, there is only about a fifty percent chance that part will solve the problem.

By replacing the part yourself, you spent a little money on a good suspect and saved much more on the mechanic's diagnostic time. Unfortunately this time it did not pan out, but you are probably still money ahead in the long run.
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Friday, August 12th, 2016 AT 11:43 PM
Tiny
SPINOU
  • MEMBER
Thanks so much for your detailed explanation! In fact, it is the mechanic who advised me to get a new speed sensor and he is the one who replaced it (cost me $160.00 for the part plus $80.00 for him) he then asked me to diagnose the car, but I am hesitating now because I do not want to waste more money if he is not sure about the issue. Do you think it is better to check this at an electrical auto repair?
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Saturday, August 13th, 2016 AT 12:00 AM
Tiny
CARADIODOC
  • EXPERT
That depends on the mechanic's experience and training. At an auto electrical shop you will find mechanics, who are good with electrical theory. At regular repair shops, you will find mechanics who typically do not like electrical work because they are not comfortable working on something they cannot see, but every shop has their specialists. For this circuit there are only going to be two or three wires, and it is not very complicated. You also have to remember there could be a mechanical problem related to the sensor. That is where you are better off with a dealership mechanic with factory training. Older speed sensors were driven by plastic gears that could break, but the sensors were pretty simply inside. Newer ones are magnetic and are triggered by a toothed steel wheel. Much less to go wrong mechanically, but there is quite a bit of circuitry inside those sensors, so they are prone to failure.
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Saturday, August 13th, 2016 AT 12:17 AM
Tiny
SPINOU
  • MEMBER
Good to know about all of this. Thanks so much for all your explanation and help! Much appreciated!
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Saturday, August 13th, 2016 AT 12:24 AM
Tiny
KEN
  • ADMIN
I would have a place that can clear the adaptation of the computer so the car can relearn to it's operation.

Only German cars have this option.

Best, Ken
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Monday, August 15th, 2016 AT 2:40 PM

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