2004 Chevrolet Impala Shifting and speedometer problems

Tiny
AWLLY
  • MEMBER
  • 2004 CHEVROLET IMPALA
  • FWD
  • AUTOMATIC
  • 94,000 MILES
Hello,
I own an impala and recently it has started to have problems. It does not always occur, but sometimes the speedometer stops working and the gears will not shift. I got it at around 80 000 miles and it was working fine, but as I use it more and more, the problem occurs more often. It did not bother me too much because sometimes it went back to normal after a few minutes, but last night I was driving on the autoroute and could not drive more than 25 m/h since I was in first gear and couldn't change. The speedometer problem is not very important to me, all it does is that it just shows as if I'm going 0 m/h. Those 2 problems always occur at the same time, so I'm not sure if it is a transmission problem or an electric problem. I'm not really good at mechanics, but I think that if it is a transmission problem I could be able to do it by myself, but an electric problem would be more complex. Any help about what can cause this problem is greatly appreciated.
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Thursday, June 19th, 2014 AT 7:30 PM

4 Replies

Tiny
CARADIODOC
  • EXPERT
Actually, you don't want to get involved with a transmission problem. Some mechanics have the training and specialize in them. Those without that training do not repair them.

What is more likely is a speed sensor is failing. That will make the speedometer read "0", and if the Transmission Computer thinks the car is going 0 mph, it's going to stay in first gear.

You didn't list the engine size so I can't look up parts, but most likely your transmission uses an input speed sensor and an output speed sensor. Normally both have to work for the road speed to be calculated and displayed on the speedometer. The best place to start is by having the diagnostic fault codes read. Many auto parts stores will do that for you for free, but usually they can only read engine codes. You may need to find a mechanic with a scanner to read transmission codes.

If there is no fault code set, scanners will display live data on a test drive, and you'll be able to see which sensor isn't generating a signal.
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Thursday, June 19th, 2014 AT 8:56 PM
Tiny
AWLLY
  • MEMBER
Great! Thanks for the quick reply.
Sorry for not specifying, but my car has a 3.4 L v6 engine. I will go see a car mechanic as soon as I have the chance, but I'm just wondering if it was possible to easily repair a speed sensor if you have the parts or would it be better to send it to the mechanic.
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Friday, June 20th, 2014 AT 5:58 PM
Tiny
CARADIODOC
  • EXPERT
Speed sensors are usually pretty easy to replace, but sensors are only the cause of problems about half of the time. There can also be wiring and connector problems. Mechanics check those things first before they spend your money on parts. For do-it-yourselfers it will cost less to buy a sensor to try, then buy a different one if necessary. Replacing random parts is not the way professionals approach problems, but for this type of problem, if you guess wrong, you will not be out too much money.
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Friday, June 20th, 2014 AT 11:53 PM
Tiny
AWLLY
  • MEMBER
Sounds good. I will see a mechanic to have the diagnostics codes and will play around with my car when I have the chance.
Thank you for your time.
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Saturday, June 21st, 2014 AT 6:15 PM

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