1996 Pontiac Bonneville Speedometer incorrect

VINNIE2U

MEMBER
1996 PONTIAC BONNEVILLE
6 CYL
FWD
AUTOMATIC
162,000 MILES

My speedometer is off by apporox. 10-15 mph. Everything else tied in with it seems to be working good - the odometer and trip odometer work ok, and even the speedometer works fine other than its off. I already replaced the VSS and now I don't know what else could be causing the problem. Any help is greatly appreciated.

Saturday, October 17th, 2009 AT 3:02 PM

3 Replies

MATHIASO

MECHANIC
1,209 POSTS

Generally if the odometer works and the speedometer does not, the problem is with the cluster. If the instrument cluster passes the self -diagnostic test but the speedometer still remains at certain speed or operate erratically, the problem is with the VSS. Good news is that you allready changed that one so, the neste thing to check for is the VSS circuit.
Check the wiring back to the sensor for short or open.
One thing, make sure that the vehicle is equipe with the proper gear ratio and tire size as either one of these can affect speedometer operation.

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Saturday, October 17th, 2009 AT 5:29 PM

VINNIE2U

MEMBER
3 POSTS

Thanks for the info. Now how exactly do I check the gear ratio? I did buy this car used and I''m fairly certain the person I bought it from got it at an auction so I don't know who did what to the car before I bought it.

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Saturday, October 17th, 2009 AT 9:13 PM

MATHIASO

MECHANIC
1,209 POSTS

TRANSMISSION 4-speed electronic automatic w/overdrive
Gear Ratios 1st 2.92
2nd 1.57
3rd 1.00
4th 0.71
Reverse 2.39
find out if there was any job done on the transmission.

TIRES
P215/65R15
P225/60R16
P225/60HR16
are the tires on the vehicle one of the size above?

Check allways the basics, wiring from the speedometer to the cluster or there is resistance problem within the speedometer in the cluster.

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