missleading dash

I have a 1997 Plymouth voyager 3.3L about a year ago the tachometer jumped up by 1000 rpm. I know this is a false reading as the car is only running at normal. This happened after I spun the wheels on some ice. Just the other day when my wife took the car the speedometer started out at 20 mph. It is now starting at 20 and will not set itself to 0 when stopped. I am now needing to adjust my speed and worry about getting a ticket. Does anyone know what is going on? How might it be repaired?
Thanks

So the speedo is reading 20mph with power off correct?

Try this:

DIAGNOSIS AND TESTING - SELF-DIAGNOSTICS
The instrument clusters are equipped with a self diagnostic test feature to help identify electronic problems. Prior to any test, perform the Self-Diagnostic Test. The self diagnostic system displays instrument cluster stored fault codes in the odometer display, sweeps the gauges to the calibration points, and bulb checks the warning indicators. When the key is in the ON position with the engine not running, the MIL will remain illuminated for regulatory purposes.

To activate the Self-Diagnostic program:
With the ignition switch in the OFF position, depress the TRIP ODOMETER RESET button. Now turn the ignition switch to the on/run position (not start).
Continue to hold the TRIP ODOMETER RESET button until Sof and a number (software version number (i.e. Sof 3.2) appears in the odometer window then release the button. If a fault code is present, the cluster will display it in the odometer display. When all fault codes have been displayed, the cluster will display “end” in the odometer display. Refer to the INSTRUMENT CLUSTER DTC'S table to determine what each trouble code means. INSTRUMENT CLUSTER DTC'S DTC DESCRIPTION
100.0 LOOP-BACK FAILURE
100.1 ABS COMMUNICATION FAULT
100.2 BCM COMMUNICATION FAULT
100.3 EATX COMMUNICATION FAULT
100.4 FCM COMMUNICATION FAULT
100.5 ORC COMMUNICATION FAULT
100.6 SBEC/DEC/MCM COMMUNICATION FAULT
200.0 AIRBAG LED SHORT
200.1 AIRBAG LED OPEN
200.2 ABS LED SHORT
200.3 ABS LED OPEN
200.6 EL INVERTER TIME-OUT
200.7 EATX MISMATCH
400.0 EEPROM READ/WRITE FAILURE
400.1 IMPROPER POWER DOWN DETECTED


CALIBRATION TEST
The CLUSTER CALIBRATION table contains the proper calibration points for each gauge. If the gauge pointers are not calibrated, a problem exists in the cluster. If any gauge is out of calibration, replace the cluster. (Nah. Remove the cluster, access the speedo needle and twist it on the shaft back to zero. May have to do this a few times)

CLUSTER CALIBRATION SPEEDOMETER CALIBRATION POINT
1 0 MPH (0 KM/H)
2 20 MPH (40 KM/H)
3 60 MPH (100 KM/H)
4 100 MPH (160 KM/H)
TACHOMETER
1 0 RPM
2 1000 RPM
3 3000 RPM
4 6000 RPM
FUEL GAUGE
1 EMPTY
2 1/4 FILLED
3 1/2 FILLED
4 FULL
TEMPERATURE GAUGE
1 COLD
2 1/4
3 3/4
4 HOT


ODOMETER SEGMENT TEST
If a segment in the odometer does not illuminate normally, a problem exists in the display.

ELECTRONIC TRANSMISSION RANGE INDICATOR SEGMENT TEST
If a segment in the transmission range indicator does not illuminate normally, a problem exists in the display.

I have preformed the testing as you posted. I can't get the display to respond doing anything in the procedures. I am assuming at this point that the instrument cluster is in bad order and will need to be replaced. Thanks for the help.

Egads! I edited the procedure (green italicized sentence) Should work now. Can't believe that wasn't there. That appears to be cut and pasted straight out of a factory manual.

I preformed the test. I receive code 999. Then it goes through check 0 thru 3. Then repeats. I don't see 999 in your list. Do you know what it means?

999 just means end of test - no failures detected. More importantly did the tach and the speedo read correctly at all 4 test values?

They bounced at the approximate spacing but they were off by the misleading amount.
I think the fuel and the temp were correct.

They bounced at the approximate spacing but they were off by the misleading amount.
I think the fuel and the temp were correct.

So the speedo was 20 mph high at each test point? Then you have a bad cluster...according to the FCM anyway. Most likely the pointers slipped on the shafts when you spun the wheels. I've read some have had success just twisting the pointers on the shaft to where they need to be. They did have to go back and forth a few times to get it right meaning adjust, reconnect, do the test then readjust and on and on till it passes the test. I've never had to do it but I'm picturing holding the shaft still with a pair of needle nose pliers probably under the pointer then twisting the pointer where it needs to be. I would consider putting a drop of super glue where the pointer meets the shaft once you're sure it's where it needs to be. Or... head to EBay or a junkyard and fork out $20 for a replacement.

Kinda where I have been heading. already priced some. Thanks for all the help it is greatly appreciated.