I TOOK MY INSTRUMENT GAUGE PANEL OUT TO REPLACE MY ODOMETER. WHEN I REPLACED AND RECONNECTED IT THE TACHOMETER AND SPEEDOMETER WOULD NOT WORK. THE OTHER GAUGES AND LIGHTS DO. I DISCONNECTED AND REMOVED THE LITTLE ODOMETER MOTOR AND AM AWAITING THE LITTLE WORM GEAR. WHAT MIGHT BE WRONG WITH THE SPEEDOMETER AND THE TACH?

You might have to replace the speedometer cable

This is one guy's advice: Replace the speedo head, that should take care of the problem."

This site is also interesting because the guy said
General Motors cars had instrument cluster problems from 2003 through 2006. When I researched instrument cluster problems on the Internet what I found raised concerns in me. Many of those vehicles had problems that began with the instrument cluster, but eventually led to the engine refusing to start.
(an electronic instrument cluster, digital instrument panel or digital dash for short, is a set of instrumentation, including the speedometer, that is displayed with a digital readout rather than with the traditional analog gauges. Many refer to it simply as a digital speedometer.)

http://www.instructables.com/id/Erratic-Instrument-Panel-on-GM-Cars/

This is a common problem with 850s. The speedometer is driven electrically, while the odometer is mechanical.

There's a tiny little gear inside the odometer that runs it from a motor; it's no longer tied directly to a speedometer cable like older models. What happens is the gear gets old and brittle and loses teeth, at which point it can no longer turn the odometer.

My wife's '96 850 had the same issue when I got it, and a little internet research turned up the answer above. There are companies that make replacement gears you can buy fairly cheaply, but it does require a fair amount of mechanical aptitude to pull the instrument panel and disassemble the speedometer assembly.

One note of caution that I learned the hard way: you have to take the front cover off the instrument panel, exposing all of the gauges. Be very careful not to disturb the position of those little needles; I ended up messing up the gas gauge, speedometer and temperature gauge, and it took a lot of trial and error to get them put back in so they showed the right readings.

If I recall correctly, I found instructions for doing the gear replacement online, but it's been so long that I don't have the web page(s) I found any more. A lot of times the manufacturer of the replacement gears have instructions on their web sites.

IPD USA sells them and has instructions.

850 Odometer Gear

After I bought my '96 850, I found it had the same problem. In my case the speedometer worked fine, but not the odometer. A little research on the internet revealed that it's a common problem with these models.

There's a motor that drives the odometer separately from the speedometer, and the weak link in the chain is a tiny gear that turns the odometer when the motor runs. That gear is easily broken and even one missing tooth will disable your odometer.

The fix is relatively straight-forward, but requires you to remove the instrument panel and disassemble it in order to get to the motor housing and the broken gear. You won't have any trouble finding replacement parts on eBay that are much better made and will last you the rest of the life of the car. The difficulty level on this is about medium, but be careful when you've got the instrument panel disassembled; I wasn't cautious enough and ended up with a couple of my indicators out of alignment; my tachometer read zero when it was idling, and my fuel gauge only went up to 17 gallons when it was full, so I had to take it all apart again to reposition the gauges to get them to read correctly.

This solution will be of great help to you,even in the case of future or other dashboard problems;
Instrument cluster consists of electronic analog gauges, various warning lights, and optional tachometer. Vehicles equipped with tachometer have an electronic vacuum fluorescent transmission range indicator (PRND3L),odometer and trip odometer display. Vehicles without tachometer are equipped with a cable-operated transmission range indicator.
Instrument cluster is equipped with the following warning lights:
Battery voltage.
Cruise (speed control).
Door ajar.
Fasten seat belt.
Lift gate ajar.
Low fuel level.
Low windshield and washer level.
Traction Control.
The Body Control Module (BCM), which receives input from various sensors, sends display information to instrument cluster and operates gauges. Instrument cluster incorporates a self-test diagnostic feature to identify electronic problems. BCM, Powertrain Control Module (PCM), and Transmission Control Module (TCM) are continuously monitored by the diagnostic system.

SELF-DIAGNOSTICS
With ignition off, press and hold TRIP and RESET buttons while turning ignition switch to ON position. Continue to hold TRIP and RESET buttons until odometer window displays CODE (approximately 5 seconds). If problem exists, system will display diagnostic trouble codes. See DIAGNOSTIC CODE CHART table. If no problem exists, Code 999 (end test) will be displayed.
DIAGNOSTIC CODE CHART
CodeDescription
110.......Cluster Memory Fault
111.......Cluster Calibration Fault
905.......No CCD Bus Message From TCM
921.......Odometer Fault From BCM
940.......No CCD Bus Message From PCM

After diagnostic code display ends, instrument cluster will go into each of the following tests in order:
Dim test.
Calibration test.
Odometer segment test.
Electronic Transmission Range indicator segment test.
Dim Test
CHEC-0 will be displayed in odometer window. Instrument cluster will dim Vacuum Florescent (VF) display. If VF displays do not dim, a problem in instrument cluster exists. See BODY CONTROL COMPUTER TESTS in BODY CONTROL COMPUTER article.
Calibration Test
CHEC-1 will be displayed in odometer window. Each of instrument cluster gauges will move sequentially through each calibration point. See GAUGE CALIBRATIONS table. If gauge needle is not calibrated properly, a problem in instrument cluster exists.

Odometer Segment Test
CHEC-2 will be displayed in odometer window. Each segment of odometer will light sequentially. If any segment does not light, replace instrument cluster.
Electronic Transmission Range Indicator Segment Test
CHEC-3 will be displayed in odometer window. Each segment of electronic transmission range indicator will light sequentially. If any segment does not light, replace instrument cluster.

The hesitates and misses is probably a chock problem, especially since when it warms up, it does great.

Since you weren't very specific on your indications, I thought a general troubleshooting guide might be helpful to you. But you might want to look on ebay for a shop maintenance manual for your vehicle if you plan on keeping it for awhile and doing your own maintenance.

This answer is applicable for many BMWs in addition to the one listed below.

Q

The tach and speedo work most of the time, but sometimes work sporadically.

A
Here is a write-up on the initial steps in tracking down a speedometer and/or tachometer problem.
Applies to: E23, E24, E28, E30, E32, E34 with speed sensor units mounted in the differential housing cover.

1) Speedometer - The speed sensor may be faulty. The sensor is mounted in the differential cover. Remove the harness plug and remove the sensor. Clean the sensor and measure the resistance (should be 0.0 Ohms). If there is any resistance higher than 0.0 (zero Ohms), replace the sensor. If the resistance reads correct, reinstall the sensor.

2) The wiring at the connector plug for the speed sensor (in the differential housing) may be faulty and corroded .... pull the boot back from the plug housing and inspect the wires and the pins.

3) The actual speedometer and/or tachometer head may be faulty. It may have a loose connection within it or a cracked circuit board.

4) The speedometer or tachometer head may be loose on the main instrument circuit board (do the gauges change or move if you smack the top of the dash, above the gauges?). Remove the instrument cluster and check the mounting of the speedometer/tachometer to the circuit board. See the attached issues of our Fast Times newsletter for assistance in removing the instrument cluster, on E30 3-series models (see the articles on replacing the PC board and replacing the odometer gears for info on the removal of the instrument cluster).

Fall 2005 Fast Times Winter 2004/2005 Fast Times
DIY E30 PC Boards DIY Odometer Repair


5) The plug that carries the impulse signal into the instrument cluster may have loose contacts. The plug for the speedometer signal is located on the driver's side of the back of the instrument cluster (on the E30 chassis). If you remove the lower dash trim panel (the one above the driver's knees), you can reach up and touch the plug. It is in a vertical position and has up to 26 wires in it. If you wiggle the plug, while driving, and the speedo comes & goes, you have loose contacts in the plug connection.

6) You may have a problem with the service interval PC board and it's NiCad batteries. If your oil change and service interval lights can not be reset (or will not stay reset for an appropriate time period), the PC board is likely faulty. This can affect the various gauges, including the speedometer and tachometer. If the PC board is faulty, I would suggest replacing it (after checking the other areas noted above). See the attached Fast Times newsletter article on replacing the service interval PC board.

In your specific case, I would suspect that you need to replace the service interval PC-board, if your service reminder lights can not be reset or do not stay reset.

Did you check the fuses?

replace instrument closter, one from a salvage unit in good condition can work and is cheaper if cost is a factor

My gas guage, speed odometer and tempiture does not work
The speed odometre is reading 9999999 what should i do

check for loose connection at the instrument cluster.