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Tom, ASE Certified Technician
Category: Car
Satisfied Customers: 25954
Experience:  ASE Certified Master Technician
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Isuzu Ascender: While driving my 2008 Isuzu Ascender at 45

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While driving my 2008 Isuzu Ascender at 45 mph the speedometer jumped to 100 mph. As I increased speed the speedometer pegged all the way. When I stopped the speedometer and turned the engine off the speed went down to 90 mph. Next time I drove it same problem but stopped at 60 mph but on return trip again went up to over 100 mph. I have driven by one of the digital speed reader signs and each time the speedometer is exactly 40 mph faster than the sign readout. Help.
Are there any added electronics to the vehicle ?Is the engine light on?
Customer: replied 4 years ago.

No added electronics. The check engine light goes on and off quite often, usually depending on where I purchase fuel, and yes it was already on when problem started

If you disconnect the battery both terminals for 15 minutes then reconnect will the system reset and no more issues?If there is still an issue its a vehicle speed sensor issue or speedometer cluster issue these need to be checked next.
Customer: replied 4 years ago.

Okay, if disconnecting the battery does not solve the problem, can my husband check and replace the speed sensor or the speedometer cluster?

Yes absolutely he needs to start with the cluster these are known to go bad..If he is handy he will have no issues.Heres how to do it its the same as the trailblazer .
Hoped this helped.Bonuses greatly appreciated.Please rate excellent service.If you rate anything lower it will leave me negative feedback so if you need further assistance please let me know thanks.

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