My tachometer and speedometer don t work

You might have to replace the speedometer cable

Speedometer
The instrument cluster receives the vehicle speed sensor (VSS) signal from the PCM through the SCP communication network. The instrument cluster micro-processor monitors the VSS input from the PCM and commands the speedometer with a corresponding movement of the pointer.

Tachometer
The instrument cluster receives the tachometer data from the PCM through the SCP network and commands the tachometer according to the data.

Taking your vehicle to a qualified repair shop that has diagnostic tool to scan the instrument cluster for DTC'S - diagnostic trouble codes an also view sensor input data to the PCM engine computer an the I/C would be your best bet .

If it used the mechanical speed cable. Check the speedometer cable attachment at the speedometer in the instrument panel. Check the speedometer cable and speedometer sending unit assembly on the transmission.

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.

If all the guages quit working at the same time, then it is probably a blown fuse. Check your fuse panels in the dash or under the hood. Look for a fuse that is labeled instrument panel or guages, it is probably blown.

check fuses pretty its gauge fuse please rate

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

that is a double sided pc board.you need to take the pc board away from the cluster,and check the reverse side of the plugs for a broken ground.

I know that on my 98 cirrus lxi, we blew the PCM thats the powertrain control modul while trying to jump start it, should be located near the fuse box near the fender

Depending on whether your speedo is mechanical (uses a cable), or electronic (uses an electrical wire to carry the signal from the sender), I would look it (what's in between the speedo and trans speed sender) before replacing the instrument panel. A good service manual that includes a dash wiring diagram should help trouble shoot this problem.
Good luck.