No CEL. I plugged in my cheap OBD II code reader just to be sure and no codes.

I briefly peered under the hood and didn't see the sensors. How is the best way to get to them. From hood, underneath or through driver front wheel well?

 

There are three sensors. One input that is near the transmission cooler tubes at the transmission, then one output sensor on the back side near the bulk head and one more for the compounder sensor. The input and output sensors are the same and can be interchangeable.

 

Got the output sensor replace. That would have been pretty easy with a normal depth 3/8 drive 8mm socket, swivel and extension. I made due with a 1/4" drive deep socket I had. Not convinced that was the problem. Took it for a test drive. Speedometer appears to show the speed but it responds slowly at times, especially when slowing down. I assume its a digital signal from the control computer to the speedometer instrument and the instrument converts it to an analog looking speed read out?

If that is so I imagine it is something mechanical with the instrument? That might be the most likely point of failure in an otherwise solid state system?

 

One more thought. Before this started happening we had the WIN replaced under the safety recall. Could the wire connecting the Computer to the Speedometer been damaged or loosened? I know they are both under the cowling but it does not appear that they would not have to remove the instrument cluster to replace the WIN

 

One more question are the 120 and 140 MPH clusters interchangable. Wife does not use the trip computer.

 

The answer is no. The speedometer get its information from the inputs from the sensors and sends via Can Buss circuit. The WIN module recall has nothing to do with the speedometer and the tech didn't need to remove the cluster. I would remove the other two sensors and check for metal debris on the sensors.

 

The input is measuring the crankshaft/engine RPM. The Tach seems to be working well. I'm not sure how that would negatively impact the speedometer. Don't know what the compounder does

 

So possible failure points:

Sensors or wires leading from sensors in the transmission of which the output sensor seems the most likely.

A solder on a circuit board in the computer or in the instrument panel.

What I have already done: replaced the output sensor with a new OEM sensor. That seemed to have no effect.


Its very easy to remove/clean the input so I will do that but I honestly expect no effect. will be pleasantly surprised if there is.

I suspect the problem is between the computer and instrument cluster since the car seems to be driving and shifting fine otherwise. A solder joint maybe makes since, since it is an intermittent failure that seems to show up more after the dash has heated up.

I think it is worth a look to get the cluster out and examine the solders with a magnifying glass.

What am I missing? Trying to tackle this like the logical engineer and experience but amateur mechanic I am

 

Took it on a long drive. Used a GPS speedometer app. Cruise control maintains a speed equal to the GPS and resumes it correctly. The instrument panel speedometer will eventually diverge from the speedometer. The results of this test drive appear to isolate the instrument panel as the failure point since tach and the computer keep the correct speed. I'm guessing its one or more solder failures tripped by heat.

Debating whether to attempt to examine and resolder the circuit elements on instrument panel or replace with a new or used IP. Do I have to go to a dealer to replace the IP?

 

I vote for resolder.