Canadian Speedo

[nards444]

Bought a new truck(16 Tradesman) that was build for canada. Everything switched over to standard good to go. But the digital speedo didnt match the analog one, the digital one was correct the analog one was 3 mph off(slower).

I had factory 17in wheels with rubber on them per the window sticker. Found OEM 20s off a 15 ram locally and swapped them out.

Now the digital speedo is 3 mph off(slower). Now that I am looking at this I dont know what analog is doing, need to check.

Did some reading this seems to be common on canadian trucks. My question is can a dealer flash the PCM to account for 20in wheels?

 

[N1ck]

This shouldn't have anything to do with it being Canadian. You changed the tire size which will effect the mph reading.

 

[kml9491]

Canadian speedos

 

[nards444]

This shouldn't have anything to do with it being Canadian. You changed the tire size which will effect the mph reading.

I got that part. But OEM before I switched was 17s and the digital and analog didnt match, GPS confirmed the digital was correct.

 

[ColdCase]

I think the cluster receives a rotational speed reading from the PCM via the CAN bus and drives both the analog and digital based on it. Perhaps a bad cluster? But I dunno.

Perhaps disconnecting the battery for a couple minutes may reset things?

There is also a cluster test mode that may reset things, but don't know how to start that on a 2016 RAM.

Is the analog gauge always off 3 mph, or is it soem % 0f speed, i.e. 3 mph at 60, 1 mph at 20? If it is always 3 mph different, then the zero point needs to be reset. Its suppose to do this on every startup.

 

[nards444]

I think the cluster receives a rotational speed reading from the PCM via the CAN bus and drives both the analog and digital based on it. Perhaps a bad cluster? But I dunno.

Perhaps disconnecting the battery for a couple minutes may reset things?

There is also a cluster test mode that may reset things, but don't know how to start that on a 2016 RAM.

Is the analog gauge always off 3 mph, or is it soem % 0f speed, i.e. 3 mph at 60, 1 mph at 20? If it is always 3 mph different, then the zero point needs to be reset. Its suppose to do this on every startup.

I would have to look at it further. But when i tested it, it was in the 50-60mph, and the digital to analog was 3mph different constant, would have to check at other speeds to verify.

I would have to run the GPS some more and see what it does at different ranges. I think the truck should be able to be reflashed for 20s, but I have a feeling it would still mean a difference between the analog and the digital.

 

[Tim7139]

I do notice mine being a few KM different, but think it is viewing angle as it does not increase in a ratio with speed and mine is a certified unit.

When I set the cruise it matches the digital read out and my GPS.

 

[nards444]

Tried it on the way to work this morning with the GPS.

Analog and digital is still off just like it was originally before I added the 20s(which are OEM)

It is progressive, up to about 40 the digital and analog are both about 1-2mph off, then once the truck gets into the 50s-70s the digital is 3-4 off and the analog is 5-6 off.

I would think dodge should be able to do a simple reflash to account for the 20s and fix the digital side. But curious as to why the analog would still be off.

 

[Hootbro]

Tried it on the way to work this morning with the GPS.

Analog and digital is still off just like it was originally before I added the 20s(which are OEM)

It is progressive, up to about 40 the digital and analog are both about 1-2mph off, then once the truck gets into the 50s-70s the digital is 3-4 off and the analog is 5-6 off.

I would think dodge should be able to do a simple reflash to account for the 20s and fix the digital side. But curious as to why the analog would still be off.

Both the analog gauge and the digital gage is getting the same vehicle speed sensor input, so nothing the dealer can do to reflash it or compensate is going to get both to match.

As to analog being out of sync with the digital, it still comes down a assembly error as the needles are probably still installed by hand.

Either way, DOT allows the new speedometer to be as much as 10% off actual speed. Most vehicles makers if they are off, are going to be to the high side of error as they do not want to liable for you having speeding tickets for being off on the low side.