95 Buick Riviera Speedometer, Odometer not working and shifting issues

[Frankythemainman]

I have a 95 Buick Riviera S/C the other day I was driving and the low voltage light came on and then went off and a second later the check engine light came on and the speedometer jumped around then hit zero and I only have 2nd and 3rd gear now, the check engine light is still on and nothing changed after I have replaced the speed sensor and looked for any broken wires in the wire harness leading to it, I also checked all the fuses and replaced the negative Terminal on the battery the transmission fluid and oil was changed a week ago any help would be appreciated

 

[HotZ28]

Sounds like the ECU/PCM had a brain fart when you disconnect the battery. What are the codes?

 

[LARRY70GS]

If the battery is bad, or has low voltage, the transmission will go into limp home mode. It will be stuck in 3rd gear with no overdrive or lock up. How old is your battery? Take a voltage reading across the battery, engine off and on. A fully charged battery should read 12.6 volts, and with the engine running, the voltage should be 14- 14.5 volts.

 

[Frankythemainman]

Sounds like the ECU/PCM had a brain fart when you disconnect the battery. What are the codes?

I can't check I don't have a obd 1.5 compatible code scanner

 

[Frankythemainman]

Sounds like the ECU/PCM had a brain fart when you disconnect the battery. What are the codes?

I can't check I don't have a obd 1.5 compatible code scanner

 

[Frankythemainman]

If the battery is bad, or has low voltage, the transmission will go into limp home mode. It will be stuck in 3rd gear with no overdrive or lock up. How old is your battery? Take a voltage reading across the battery, engine off and on. A fully charged battery should read 12.6 volts, and with the engine running, the voltage should be 14- 14.5 volts.

The battery reads 14.7 volts when running and 12.76 not running and it about 4 months old

 

[HotZ28]

I can't check I don't have a obd 1.5 compatible code scanner

If you plan to keep the car & do your own service work, you need to get one of these:
Elite AutoScanner Kit - Enhanced OBD I & II Scan Tool | OBD 1300