No instruments, guages or lights.

You have no idea what your messing with . Theft light on , DTC'S - diagnostic trouble codes stored . Before you start replacing BCM an making matters worse ,do yourself a favor an take it to a qualified repair shop .
The powertrain control module (PCM) communicates with the instrument cluster using serial data over the UART serial data bus, CKT 800. When the instrument cluster determines a Pass Theft condition, the instrument cluster sends a coded password to the PCM. When the instrument cluster receives the correct password, the PCM enables the fuel injection system in order to allow the vehicle to operate normally. The PCM may allow the vehicle to start and stall quickly during a failed theft condition.

The Passlock™ lock cylinder is a locking cylinder that turns a rotating magnet past a stationary hall effect sensor. The rotating magnet creates a resistance code (R-Code) that the cylinder sends to the instrument cluster. The Passlock™ lock cylinder interfaces with the instrument cluster through a 3 wire connection. The 3 wires have the following functions:
• Power
• Ground
• Data
The THEFT SYSTEM indicator will not light under any circumstances.
Replace the instrument cluster.
For Chevrolet vehicles, refer to Instrument Cluster Replacement .
For Pontiac vehicles, refer to Instrument Cluster Replacement .
Multiple indicators light continuously.
Test for a loss of serial data. Refer to Data Link Communications System Check .
Instrument cluster DTC B1021 sets.
The DTC indicates a loss of powertrain control module (PCM) serial data. Refer to Data Link Communications System Check .
Instrument cluster DTC B1022 sets.
The DTC indicates a loss of SIR serial data. Refer to Data Link Communications System Check .
Instrument cluster DTC B1023 sets.
The DTC indicates a loss of ABS serial data. Refer to Data Link Communications System Check .
Instrument cluster DTC B1011 sets.
Refer to DTC B1011 Passlock Cyl Data Shorted This Ign Cycle in Instrument Panel, Gauges and Console.
Instrument cluster DTC B1012 sets.
Refer to DTC B1012 Passlock Bad R-code This Ignition Cycle in Instrument Panel, Gauges and Console.
Instrument cluster DTC B1013 sets.
Refer to DTC B1013 Passlock Bad Timing This Ignition Cycle in Instrument Panel, Gauges and Console.
Instrument cluster DTC B1014 sets.
Refer to DTC B1014 Passlock R-code Unprogrammed in Instrument Panel, Gauges and Console.
Instrument cluster DTC B1015 sets.
Refer to DTC B1015 Passlock Cluster Fail Enabled in Instrument Panel, Gauges and Console.
Instrument cluster DTC B1017 sets.
Refer to DTC B1017 Passlock R-code Learn Failed in Instrument Panel, Gauges and Console.
The indicator flashes and no instrument cluster codes are set.
Refer to DTC B1013 Passlock Bad Timing This Ignition Cycle in Instrument Panel, Gauges and Console.
So , do yourself a favor an have a qualified repair shop check it out .

At the moment, your instrument cluster maybe faulty? Due the basic tests, try to be sure. Check for applicable trouble codes relating to instrument cluster--pcm--communication codes. Some of the national brand auto stores in this country may check codes for free, if there are any.
Check voltage and ground circuits for the instrument cluster. The sending units for gages are wired to pcm then the pcm sends serial data to instrument cluster telling instrument cluster what to do with gages. If you want to check gage sending units, that's ok.

If you have a scanner that can communicate with instrument cluster, you can get instrument cluster to do a self-test. The self-test, the instrument cluster will turn warning lamps on and off, sweep gages w/o outside data input. The instrument is considered good, if it passes that test, if not, the instrument cluster is considered faulty.

Some electrical short stay there, I suggest to check each electrical circuit that is connected to this fuse; check description or legend in the fuse label. With other details, we could send some electrical diagrams.

The problem sounds like the battery has run down. Even though the ignition is off, things like clocks and the radio draw small amounts of power to retain their settings, and the instrument cluster doesn't draw as much power as the starter. It usually takes about a month or so to drain the battery. Try jump starting the car, or put it on a battery charger for a while.

Sounds like you have a power drain (small-amperage short) in the wiring going to your instrument cluster. The short has disabled some of your instrument cluster lights, but, since is has high resistance, it has not blown a fuse (since it draws to few amps). Once the current drain has wasted enough amperage, there's not enough left in the battery to start the car.
Phase 1: Interim solution: (1) charge the battery with your battery charger (if you don't have a battery charger, attach the battery with jumper cables to the battery in a running car - its alternator will charge your battery).
(2) pull the fuse(s) to the instrument cluster, thus killing power to the short.
(3) start and use you car without instrument cluster lights until you can move
to phase 2 of your repair. If you're not sure that you've killed power to the short, disconect the battery each time you stop the engine.
Phase 2:
(1) isolate the problem (the short) to one specific fuse, meaning one specific branch circuit in the car.
(2) trace the wiring from the fuse block to the instrument cluster, looking for
burn marks, bare wires (all wires should be insulated), or anything touching
a frame ground. Also look for moisture iintrusion - water can cause these types of high resistance "shorts" - with the symptom that the problem disappears after the water dries up.
(3) correct wiring problem found in step 2, plug in fuse. done
(4) if replacing instrument cluster, use instructions below.

1995-99 Models

See Figure 4
Fig. 4: Common instrument cluster found in 1995-97 "S" series Pick-ups.
(see illustration at end of message)

1. Disconnect the negative battery cable.
2. Remove the sound insulators/trim panels.
3. If necessary for access, unfasten the steering column nuts and if necessary, the bolts at the lower flange, then lower the column for access.
4. Unfasten the instrument cluster bezel screws located at the lower edge of the bezel. If no screws are present, then remove the bezel by pulling it straight out.
5. Unfasten the four screws retaining the instrument cluster to the instrument panel, unplug any necessary cluster electrical connections, then remove the cluster.

To install.
6. Install the cluster to the instrument panel making sure the cluster is firmly seated onto the connector, attach any necessary electrical connections and tighten the cluster fasteners to 17 inch. lbs. (1.9 Nm).
7. Install the instrument cluster panel bezel by snapping it into position, then if equipped, install the screws along the bottom of the bezel.
8. If lowered, re-position the steering column and tighten retaining nuts to 22 ft. lbs. (30 Nm) on 1995 models. On 1996-99 models tighten the nuts to 20 ft. lbs. (27 Nm). If removed, tighten lower flange bolts to 120 inch lbs. (13 Nm).
9. Install the sound insulators/trim panels.
10. Connect the negative battery cable.

LOOK AT THE RELAY GENERALLY A HOLE INSTRUMENT WONT GO OUT WITH OUT A FUSE BLOWING OR A RELAY THE HOLE THING IS ONE UNIT BUT RAN SEPERTLY

the instrument cluster is probly failin-can happen with age or if u spiked it by puttin a new battery in car-these things are really sensitive to voltage swings--may also be a wiring issue too--get car scanned at a discount place and buy a haynes manual

A replacement instrument cluster sells for roughly $600.00 and needs to be reprogrammed for your vehicle. The cluster houses the theft deterent function in it.

check ignition fuse to dash lights.if all is good you could have pcm problems.

The p1687 code is a NO MIC BUS MESSAGE( mechanical instrurment cluster). When replaced the guages did you replace the whole cluster? here is the diag for this code. 48 Turn ignition on, Engine not running.
Using the DRB, erase codes.
Cycle the ignition key on and off several times.
With the DRB read PCM trouble codes. LOOK for P1687.
Did the No PCI Bus Message from MIC trouble code return?

Yes ® Go To 50
No ® Go To 49
49 Turn the ignition key on, Engine not running.
Does the Odometer in the Instrument Cluster display No Bus?

Yes ® Go To 50
No ® Go To 51
50 Turn ignition off.
Disconnect the PCM.
Disconnect the Instrument Cluster Connector.
Using an ohmmeter, measure the PCI Bus Circuit between the PCM and the
Instrument Cluster Connector.
Is the resistance below 5.0 ohms?

Yes ® Replace the Instrument Cluster.
Perform Powertrain Verification Test VER-1A.
No ® Repair the open PCI Bus Circuit.
Perform Powertrain Verification Test VER-1A.
51 Turn ignition off.
Note: Visually inspect the related wiring harness. Look for any chafed,
pierced, pinched, or partially broken wires.
Note: Visually inspect the related wire harness connectors. Look for broken,
bent, pushed out, or corroded terminals.
(DRB is the factory scan tool you can use subtitute if you have access)