Replaced bad instrument dash panel on 04 malibu lt with used one from 05 malibu.everything works fine but gear indicator now reads low gear when floor shifter is in drive,was ok before changing

Make sure your ignition switch is working first (does everything light up and working with the key in "ON" position) then try ACC position, does the radio work? If all that checks out then it would be the stepper motors on the instrument cluster are bad, there are several repair kits available pretty cheap since they are a common problem

I recently had my engine replaced in my 2002 grand marquis 4.6 with a 2009 crown Vic 5.4 engine and was running fine until I broke my ignition and tried to replace it myself I bought a new ignition switch didn't work so I bought a steering column and still won't start what do I d?
I landed on this website reliable-store.com and they got me free manuals so I used it to repair and it works fine

Could be the stepper motor in the instrument cluster . GM instrument cluster had bad stepper motors . 2003 to 2006
How to repair GM Instrument Cluster Speedometer Gauge Stepper

Every light lit on the instrument cluster , could be data network problem . Do you know what a serial data network is , class 2 or GMLAN ? Hooking up a professional or factory scan tool to view sensor data to ECM - engine computer .
Fuel Gage
The instrument panel cluster (IPC) displays the fuel level as determined by the engine control module (ECM). The IPC receives a serial data message from the ECM indicating the fuel level percent. The fuel gage defaults to empty if:
• The ECM detects a malfunction in the fuel level sensor circuit.
• The IPC detects a loss of serial data communications with the ECM.
When the fuel level is less than a pre-determined value, the IPC illuminates the low fuel indicator.

You have a switch on the instrument panel ?
The NVG 263 transfer case features a three button shift control switch located on the instrument panel
The NVG 236/246 transfer case features a 4 button shift control switch located on the instrument panel.
Or
The New Venture Gear (NVG) 261, RPO NP2 transfer case is a two-speed, part-time with "mode shift-on-the-fly" capability. It has a chain driven front output shaft and an epicyclical low range planetary arrangement. The NVG 261 transfer case features a four position shift lever control located in the vehicle floor plan. As required, the operator can select 4HI position from 2HI "on-the-fly," as described in the owners manual. A dash 4WD lamp will continue flashing during shifting, until all criteria have been met and the new mode/range position has been reached. Once the new mode/range position is fully engaged and the front axle disconnect locks in, the dash light 4WD indicator lamp will remain ON constantly. Range shifting functions similarly, although it should be limited to speeds 8 km/h (5 mph) or less.

Transmission Floor Shift Control Indicator Lamp Replacement

Remove the front floor console. Refer to Front Floor Console Replacement.
Rotate the floor shift control indicator lamp socket (2). Pull the socket from the trim bezel.
Remove the bulb from the socket.

Front Floor Console Replacement

Preliminary Procedures
Remove the rear floor console. Refer to Rear Floor Console Replacement.
Remove the instrument panel lower trim plate. Refer to Instrument Panel Lower Trim Plate Replacement.
Set the parking brake, then shift the transmission into drive and push the shift indicator down until it locks, to allow clearance to remove the console.
1
Front Floor Console Screw (Qty: 2)
Caution: Refer to Fastener Caution in the Preface section.
Tighten
2 N·m (18 lb in)
2
Front Floor Console Bolt (Qty: 2)
Tighten
10 N·m (88 lb in)
3
Front Floor Console Assembly
4
Front Floor Console Retainer Clip (Qty: 2)

The odometer will display 'error' if an internal IPC memory failure is detected or if there is a serial data communication fault between the ECM and the BCM. IPC instrument panel cluster .
Circuit Description
The communication among control modules is performed through the GMLAN high speed serial data circuit and the GMLAN low speed serial data circuit. The modules that need real time communication are attached to the high speed GMLAN network. The body control module (BCM) is the gateway between the networks. The purpose of the gateway is to translate serial data messages between the GMLAN high speed buss and the GMLAN low speed buss. The gateway will interact with each network according to that network's transmission protocol. Refer to Body Control System Description and Operation for more information about the gateway.
Your best bet is to take your vehicle to the dealer , sorry !

The problem could be a wiring issue or connection problem at the instrument cluster. It also could be the instrument cluster is bad and has lost communication with engine control module.

GM Tech 2 support for on-board diagnostics on all GM systems 1992 thru 2011.The following GM vehicles utilize the CAN interface:

05 Buick Allure (3.6L)
05 Buick LaCrosse (3.6L)
05 Buick Rainier (5.3L)
04-05 Buick Rendezvous (3.6L)
04-05 Cadillac CTS (3.6L)
04-05 Cadillac SRX (3.6L / 4.6L)
04-05 Cadillac XLR (4.6L)
05 Cadillac STS (3.6L / 4.6L)
05 Chevrolet Cobalt (2.2L)
05 Chevrolet Corvette (6.0L)
05 Chevrolet Equinox (3.4L)
05 Chevrolet TrailBlazer (5.3L)
05 Chevrolet SSR (6.0L)
04 Chevrolet Malibu (Body/Chassis only)
05 Chevrolet Malibu (3.5L)
05 GMC Envoy (5.3L)
05 Pontiac G6 (3.5L)
05 Pontiac GTO (6.0L)
05 Pontiac Pursuit (2.2L)

Likely you have a bad connection on one of the dash connector plugs. Generally if they come on when you smack the top of the dash when they go off that verifies it. If so, remove the dash face and gauge panel (use manual) and clean contacts.

just unhook the battery for about ten minutes and hook it back up... that should do it