Speedometer not functioning

Hi,

I attached the detail about how the speedometer works. Basically, the PCM sends the signal to the cluster where the speedometer displays that signal. So if the cluster is not displaying the correct speed or any speed at all them most likely the cluster has failed.

When you send the cluster to a vendor to have it tested, all they are doing is applying voltage to the circuit for the speedometer and if the needle responds then they say it is good. This is not an accurate test. You actually need to perform the actuator test that is talked about in this attachment to determine if the cluster can respond properly. This will send specific voltages and the needle will need to go to a specific point on the speedometer. If it does, then it is ok and you need to look at wiring or the PCM.

The fact that you have no codes, I suspect the cluster is the issue because there is no code for a malfunctioning speedometer. Also, the PCM gets the speed from the wheel speed codes and there are codes for each of those. The PCM then sends the signal too the cluster via the communication network and this is monitored for issues so if the cluster was getting a bad signal or no signal, I would suspect you would have a code plus other gauges would not be working because the PCM sends that signal as well via the same signal.

The actuator test is done with a scan tool so if you don't have one we will need to have a shop look at it that can do that.

Let me know if you have questions. Thanks

It is possible that it is a wiring issue and it gets intermittent connection so it will work while it has connection then the connection fails again and it is back to not working. However, the more likely cause because this is called a "bussed input" that the cluster circuit board has this connection issue and when it is hotter outside the connection fails because the metal on the circuit board is expanding causes the loss of connection.

Let me know if this makes sense. Thanks

Take a look at the attachment then I will try to decipher it for you.

Basically, it is telling you that you cannot use a used cluster because the features are programmed into it according to the first VIN that is plugged in. Meaning the new cluster is blank and as soon as it is plugged in and turned on, the PCM and FCM tell the cluster how that VIN is equipped and that is how it stays.

However, if you get a used cluster out of a similarly equipped vehicle then you can use it. If you don't then some of the functionality that your vehicle has may not work if the cluster you are putting in it came out of a vehicle that didn't have it.

If you look and find one, feel free to get the VIN of the vehicle it came out of and then provide me your VIN and I can tell you if they are close enough.