When I’m doing short daily trips, the speedometer seems to be normal. When I go on a long trip, the speedometer starts saying I’m going faster than I’m actually going. As the trip gets longer and longer, the reading gets higher and higher. On my last trip a couple days ago, the needle maxed out and stay there for the remainder of the trip. When I stopped it would drop down to 100km/h, but one I got moving it would soon be maxed out again. Now that I’m back home, doing short daily trips, it’s back to normal again. I’m hoping to get some ideas from others on where to start with this. I suspect there’s nothing wrong with the x24 Crankshaft Position Sensor (CKP) behind the crankshaft pulley/damper because the speedometer needle still changes with the speed. I’m suspecting that there might be a problem with the speedometer itself, but I don’t know. I did hear a clicking sound coming from the instrument panel area when I first bought the van earlier this year. The clicking seems to be gone, but now this problem. The cruise control is working good. Everything else on the instrument panel is working normal. Only the speedometer has an issue.
The crankshaft position sensor has nothing to do with the speedo.
The instrument cluster is likely bad.
Could be a bad stepper motor. Cheap fix if you are handy.
It was my understanding that the PCM uses the signal from one of the crankshaft position sensors, along with the gear ratios and wheel diameter to calculate the vehicle speed. So if you don’t think the crankshaft position has anything to do with it, do you know where the PCM gets the information from?
Vehicle Speed Sensor or VSS in the transmission.
If the Check Engine light isn’t on, it’s not the VSS.
Tester
You are right. Even my Hayne’s manual says it’s on the transaxle.
No the check engine light isn’t on. It hooked up my code reader and saw that the P1811 code is in the history a few times over the past couple months.
Then the instrument cluster (speedometer) is probably faulty.
Tester
From my experience, stepper motors. By the time I replaced them in my 05 Lesabre, I was setting land speed records 
Funny, my speedometer states “Ground Speed”, no “Air Speed” indicator. Just one of those things designers add, though I have (unintentionally) been airborne in cars.