I have a bad cluster in my 2000 mustang 3.8ltr from what the diagnostics at the dealership said. Would i need to have the computer reflashed if i replaced it with a cluster off another mustang 3.8 ltr or would it work without any problems??

plug test light, coil packs? pressure test, check heads, valves, fuel injector? going to need a diagnostic on that one, unless you got the tools, take it to the er and get a rundown, anyone with a proper diagnostic computer should be able to do it

Could be the speed sensor in the transmission.
Is the check engine light on and did you have the computer scanned for trouble codes ?

You have a major BCM fault, and/or instrument cluster malfunction...
You will need a high end diagnostic scan and a possible reflash done.

use a scan tool to reset the ECM to get the immobilizer to work

You are going to have to get the security system reset. You will probably have to contact the dealership if you don't have the code.

GM had gauge cluster problems from 2000-2005. Bad stepper motors. On those units you have to replace the cluster or rebuild it with new stepper motors. Dealership fixed mine for $150.00

Sounds like you have a instrument cluster going bad,but I have repaired some concerns like this at the dealership with a reflash downloaded by there Tech2.

The instrument cluster has to be programed to your keys. You will need two keys and someone to program them to the cluster.

mustangs of your year are known for having defective stepper motors installed in the gauge cluster. Having someone replace the bad motor with the newer p/n motor should be a lot cheaper than replacing your cluster at the dealership.

From the official Durango shop manual......(abbreviated)

Self Diagnosis Test

Vehicle key position is OFF ,or able to pull key out.
Hold in the trip odometer button (dont release yet)
Turn key to the ON position (one notch), but DON'T try to start the engine
Continue holding the trip button for about 10-12 seconds until CHEC appears in the odometer display
Release the trip button.
Series of three digit numeric failure codes may appear.
If no failure message appears, the self diagnostic test will proceed as described in step 6


Code Chart

110- cluster CPU,RAM,EEPROm failure, replace cluster

900-CCD data bus not operational, check CCD data bus connections at cluster, check the cluster fuses,check the CCD data bus bias, cehck the CCD data bus voltage, check the CCD data bus terminations.

920-cluster is not recieving a vehicle speed message from the PCM, check PCM software level and reflash if required, use the ($2500+) DRBIII scan tool to verify the vehicle speed message is being sent by the PCM

921-the cluster is not recieveing a distance pulse message from PCM,check PCM software level and reflash if required, use the ($2500+) DRBIII scan tool to verify the distance pulse message is being sent by the PCM

940-the cluster is not recieving an airbag lamp-on message from the ACM, check the CCD data bus connections at the ACM, check the ACM fuse.

950-cluster not recieving an ABS lamp-on message from the CAB, check CCD data bus connections at the ACM, check the ACM fuse.

960- clsuter not recieving a PRND21 message from the TCM, check the CCD data bus connections at the TCM, check the TCM fuse.

999-An error has been discovered, record the failure message, depress the trip odometer reset button to continue the Self-Diagnostic Test

Step 6
Instrument cluster will test each segment of the odometer (all first, then each one seperately)

Step 7
Bulb test

Step 8
Gauge test

Step 9
test completed

The instrument cluster will return to normal operation at the completion of test, if ignition switch turned off, or a vehicle speed message indicating movement recieved from the PCM on the CCD data bus.

Hope that help you or anyone else in future.