speedo problem?

[wyochimneysweep]

ok was on a road trip of 1600 miles and was bored so plugged in scan tool and looked through the data and the ecm showed 55mph when the speedometer showed 65mph set on cruise. I thought the speed was from the transfer case speed sensor for both the intresment cluster and ecm or i'm i wrong here?

 

[BrooklynBay]

Did you change your tire size or are they the same stock size? Are all 4 tires the same size?

 

[wyochimneysweep]

Did you change your tire size or are they the same stock size? Are all 4 tires the same size?

Stock tire size of 235/75r15 and they are brand new. only the trip is on them

 

[wyochimneysweep]

but what i was getting at is the computer reading a different speed then the speedo. even if i changed the tire size they should read the same speed

 

[fixxxer]

Were stock rims on a 2nd gen 15's or 16's? I know 1st gen Ex's are 15" but 2nd the gens?

 

[wyochimneysweep]

mine are stock and there 15's window sticker show 235/75r15 as the optition brought

 

[wyochimneysweep]

i guess what i'm asking is there more then four sensors for speed? one in the transfer case and the two in the front hubs which are abs and the one in the rear dif thats also for abs

 

[BrooklynBay]

The front sensors always get messed up with brake dust. Did you clean them with brake cleaner spray?

 

[fixxxer]

The VSS is a gear driven electronic switch, if the gear slips or is the incorrect size maybe? the ABS sensors do work off of rotational forces but the PCM doesn't use the abs for the speed sensor circuit.

 

[BrooklynBay]

Check # 3 in my list of useful threads for more information: http://www.explorerforum.com/forums/showthread.php?t=158739

 

[fixxxer]

That really is an impressive list you have there Brooklyn. Very good job!

 

[BrooklynBay]

Thanks! I'm always adding things to it as I see something which is worth while.

 

[wyochimneysweep]

so i know mine doesn't have a cable its electic. now why does the ecm see different speed then the dash?

 

[patrick112390]

hey guys i need your help i have a 97 mounty with the bw AWD t-case.. reciently my speedometer has been screwin up like goin up/down between my speed and 0 and then stay there. i know it isnt the cluster because i can bang it and it does nothing, however i just replaced the VSS and that didnt make a difference......

where should i go next?

 

[patrick112390]

hey guys i need your help i have a 97 mounty with the bw AWD t-case.. reciently my speedometer has been screwin up like goin up/down between my speed and 0 and then stay there. i know it isnt the cluster because i can bang it and it does nothing, however i just replaced the VSS and that didnt make a difference......

where should i go next?

oh and btw its electric (side on rear of transfer case)

 

[patrick112390]

heres a good vid if anyone has run into this problem?

http://www.youtube.com/watch?v=nGzg6R_J5N0

i was doin 65 by the speedomter.......

 

[fsumotorhead]

sound like the gain on the speedo gauge needs adjusted to match what the PCM is reading.

 

[wyochimneysweep]

pat you need to hook up a scan tool and watch the vss speed and if it stays steady then its going to be the cluster. where is the gain on the speedo head. and if its reading 10 mile faster a hour then why do i pass everyone on the road and the radar sites that give you a reading shows what my speedometer shows and not what i see on the scan tool?

 

[wyochimneysweep]

I'll take the other scan tool out and double check that my snap on scan isn't readiong it incorrectly

 

[patrick112390]

sound like the gain on the speedo gauge needs adjusted to match what the PCM is reading.

can you explain what you mean here?

pat you need to hook up a scan tool and watch the vss speed and if it stays steady then its going to be the cluster. where is the gain on the speedo head. and if its reading 10 mile faster a hour then why do i pass everyone on the road and the radar sites that give you a reading shows what my speedometer shows and not what i see on the scan tool?

im pretty sure its not the cluster because when it is staying at zero and i bang the dash, it doesnt move which it usually would if it was the cluster....