My speedometer not working and not sure why. So I had the heater core replaced and the shop that did it had also disconnected my aftermarket stereo and had just pushed all the wires back in the stereo slot and never told me. So I fixed that and also Installed my tt chip and injectors so I'm not sure if I disconnected something somewhere or shop did. Anyone know where I should start to look? My scan master will read the mph so that should eliminate the sensor being bad right? The speedometer worked fine before so I'm confused on where the problem is.
Speedometer not working
- Thread starter Troyphoon
- Start date
Mephisto
These trucks are cursed
Re: Speedometer not working
Try dropping the ECM from under the dash and make sure the harnesses are secure or even reseat them... maybe try popping that TT chip out for a minute and see if it works without it...
Otherwise you might have to have someone ride shotgun and wiggle the harnesses and wires around while you're driving to see if the speedo pops up for a second.
If you're getting a reading through scanmaster, then it's gotta be the wires going from the speedo to the ECM. Also, check the harness itself... wouldn't be the first time one of those wires pulled out of the harness.... and better the speedo than the fuel gauge haha.
Try dropping the ECM from under the dash and make sure the harnesses are secure or even reseat them... maybe try popping that TT chip out for a minute and see if it works without it...
Otherwise you might have to have someone ride shotgun and wiggle the harnesses and wires around while you're driving to see if the speedo pops up for a second.
If you're getting a reading through scanmaster, then it's gotta be the wires going from the speedo to the ECM. Also, check the harness itself... wouldn't be the first time one of those wires pulled out of the harness.... and better the speedo than the fuel gauge haha.
Re: Speedometer not working
Thanks for the reply. Yeah I'll check this week when I install the tuning stuff.
Thanks for the reply. Yeah I'll check this week when I install the tuning stuff.
Don W.
Stab it and steer it
Re: Speedometer not working
The wire from the DRAC (not the ECM) to the spedo is the lt-blu/blk Apparently that's it. So it would seem that if you're getting a reading from Scanmaster you should check that wire. If the torque converter locks-up like it's supposed to then presumably the ECM is getting speed info as well but I'd have to check that.
The wire from the DRAC (not the ECM) to the spedo is the lt-blu/blk Apparently that's it. So it would seem that if you're getting a reading from Scanmaster you should check that wire. If the torque converter locks-up like it's supposed to then presumably the ECM is getting speed info as well but I'd have to check that.
IGottaSy
Active member
Re: Speedometer not working
Looks like speedo shares 2 connections in wiring schematic with tach. If tach works, then trace 824 from speedo going to W on harness plug behind gauge cluster. See if that goes thru across where radio is located toward ECM. Follow it on schematic all the way to ECM. Maybe the "mechanic" tugged on wire harness to facilitate his job?
Looks like speedo shares 2 connections in wiring schematic with tach. If tach works, then trace 824 from speedo going to W on harness plug behind gauge cluster. See if that goes thru across where radio is located toward ECM. Follow it on schematic all the way to ECM. Maybe the "mechanic" tugged on wire harness to facilitate his job?
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