2004 Impala Speedometer

SRQSPEEDY

MEMBER
2004 CHEVROLET IMPALA

2004 Impala, 44,000 miles recently experienced malfunction of speedometer. After driving a short distance in intown traffic, I noticed the "needle" was at the 110 mph mark, and moved ahead to the 150 mph mark. When coming to a stop it returned only to the 110 mark. All other electrical systems are functioning normally. What needs repairing and is it something that I can do myself?

3 Replies

DEMEARSJR

MECHANIC
110 POSTS

Could be a vehicle speed sensor, or the needle got whacked out of alignment.

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Friday, July 28th, 2006 AT 12:48 AM

SRQSPEEDY

MEMBER
2 POSTS

[quote="demearsjr"]Could be a vehicle speed sensor, or the needle got whacked out of alignment.[/Quote]
Thank youfor the reply. What I am interested in knowing is, is this something I will need to return to the dealership for or can I use a local certified mechanic to do the repair and do you know about how much I am looking at spending.

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Friday, July 28th, 2006 AT 3:31 PM

MIKEYBDMAN

MECHANIC
623 POSTS

Read this first:

The IPC displays the vehicle speed as determined by the IPC. The IPC calculates the mileage based on the class 2 vehicle speed message from the PCM. The IPC calculates vehicle speed based on the class 2 wheel speed message from the EBCM if a loss of communication or malfunction occurs with the PCM. The speedometer defaults to 0 km/h (0 mph) if the IPC detects a loss of class 2 communications with both the PCM and the EBCM.

Now, I would suspect if it saw a malfuntion of the PCM signal, it would have refered to the EBCM signal, or go to "0". With that said, it is eaither your IPC not displaying the correct speed from a good signal from the PCM, or the PCM sending a bad signal to the IPC. I would therorize that the PCM would have a way to determine if the signals it is looking for from speed sonsors was invalide, and probably send a error code. I would also think that more symptoms would be present if a sensor was giving bad info. But all of this is just guessing, your best bet is to probably let the dealer test it out. You should have a warrenty on that car, so have them fix it for you.

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Friday, July 28th, 2006 AT 4:58 PM