Cheers everyone,

I am still trying to get my cruise control running.
I can switch it on, but at about 40mph it switches itself off on its own. I can then only switch it on again when going below 40mph.
What I did already:
replaced rear differential speed sensor
replaced front hub including speed sensor (NTN/BCA)
Checked ABS controler connections, all seem to be good (no visible corrosion or anything).

Now I also get a P1501 from time to time.
So, what might be the culprit here? Bad wiring somewhere? Or bad passenger side sensor?

 

Do you have the same size tires front and rear? Tire pressures good?

 

Yeah, 315/70R17 all around. I even set the correct tire size with my Diablosport Predator, but didn't change anything.
I also tried changing the tire size to somewhat "extreme" sizes to test.
So when the correct tire size was set, the cruise control would shut off at 53-54kph (GPS measurement)
When setting it to 17.5 inch tires (LOL) it would shut off at 61kph (GPS measurement)

So it does change with tire size programmed.

 

Well, the code is talking about sensor 1/2 correlation..... So, it seems you have a couple sensors that don't agree with each other. I don't know for a fact which sensor is which, but, I suspect 1 and 2 are the left front, and the sensor on the pig on the rear diff. Unless you have a sensor at each rear wheel, then I don't have a clue.

Can you see data from the various speed sensors on your scanner? Might be interesting to see what they all have to say as you accelerate. (second warm body to drive while you read data is HIGHLY recommended. )

 

Are you sure it is about sensor 1/2 correlation? The scanner says something like "Vehicle Speed Sensor Out of Self Test Range" though.
I have two sensors in the front, one on each wheel, and one in the rear on top of the back differential. Front left and rear one are new sensors already, still same problem.

Unfortunately I can't see that data though
Speedometer is working correctly all the time, never "jumps" or anything.

 

Not being able to actually see the data seems like a serious oversight to me..... That was invaluable to me back when I was doin' this for a livin'..... This is one of those occasions that WITH the data, you would see the problem in seconds, without it...... you are just guessing.

Also, that was the definition for the Dodge P1501 I found.... Does that mean I am correct, and the scanner is misinformed? Nope...... Things change over the years, and not all of them are consistent.

I would dearly love to be able to buy a limited copy of the software that the manufacturer uses to diagnose their systems..... Even if it was tied to a single VIN, for a reasonable fee..... it would make our lives SO much easier.

Theoretically, the code means the computer sees rear wheel speed being higher than the front.... So, it's *possible* the the one sensor you HAVEN'T replaced could possibly be the culprit....... But, without the data, that is just a guess.

 

Yeah, that really would make it easy.
I will maybe ask the shop I went to last time if their SnapOn scanner can read that live data.
A few months back I tried a chinese copy of that WiTech adapter with DRB III software emulator, but that didn't work though.
So only data I can see is the error messages and engine live data.

So yeah, your definition would make sense, as the engine controler sees different speeds and tells that something is wrong and switches off the cruise control.

But from what I read everywhere is that the front left and rear sensors are used for cruise control.
But maybe due to that error it stops it?
ABS is working though...

 

That's just bizarre.

The sensors are working for one system, but, not for another????? I don't get that one at all.

Yeah, one of the high-zoot snap-on scanners may actually be able read that data. My truck is a 98, and so far, I haven't found a scanner that will show me any meaningful data... I can't even see misfire counters. Something that the old MT2500 snap-on scanner could see on OBDI vehicles..... Ain't technology wonderful?

 

Yeah, I don't really know how these systems work. I think ABS has a seperate controller, so needs all 3 sensors to work. Cruise control is controlled by the PCM and uses front left and rear sensor. That was the explanation I read somewhere.

And yeah, reading live data on these cars really is a nightmare! I am so glad the guys at DiabloSport helped me out getting my device running for free (!) so I can at least see all the trouble codes and not just the ones I can read with the OBDII...

 

I searched around in some PDF documents and now found this explanation:
P1501-VSS 1/2 CORRELATION - DRIVE WHEELS When Monitored: Ignition on and vehicle moving. Cruise is learned. Set Condition: The PCM recognizes rear axle speed is greater than front axle speed

So it seems like it is not accepting the front left sensor because the speedometer is working just fine. But it also does not give any ABS code and ABS seems to be working...