HELP! TPS and Tach Sensor Problems
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Senior User
Joined: Dec 2006
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From: Fulton IL
HELP! TPS and Tach Sensor Problems
Well guys, I just got done throwing my new to me 94 engine in my 90. Well it runs and drives, but I have 2 problems.
The first is: I dont have a working tach. It moves a little when cranking but when it starts, it doesnt move at all. I switched the sensor from the motor I took out, but still no go.
Second is: I was going to set the TPS, and I am getting almost 12v at the center pin. When I move the throttle to WOT, the voltage goes down. What could be causing this?
The first is: I dont have a working tach. It moves a little when cranking but when it starts, it doesnt move at all. I switched the sensor from the motor I took out, but still no go.
Second is: I was going to set the TPS, and I am getting almost 12v at the center pin. When I move the throttle to WOT, the voltage goes down. What could be causing this?
Lead Driver
Joined: Mar 2006
Posts: 5,098
Likes: 1,504
From: western SD
Which wiring harness was used on the install? If the tach worked before the install of the 94 motor, and the wiring harness from the 94 motor was used, maybe a bad wire or connection. Can't help on the TPS, not an auto guy.
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Senior User
Joined: Dec 2006
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From: Fulton IL
Figured it out!
I tore all the loom off of both harnesses. turns out the small round connector on the 90 harness runs the tach and has a 12v key on wire, and the larger round plug runs the TPS and A/C switches. On the 94 harness, the small plug runs the TPS and the larger plug does the rest. Thats why I was getting 12v to the TPS
I never would have thought this would be. The connectors are the same with the same amount of pins and the pins were in the same location in the plug. I spent two days screwing with this stuff, without tearing the loom off, I dont know if I would have figured it out.
So if anyone is ever swapping a newer motor... use the original harness to the truck for this. Only modification, was to use a heat shrink adhesive lined butt connector to hook up the key on power wire to the wire from the alternator. It was a green with a red stripe
I tore all the loom off of both harnesses. turns out the small round connector on the 90 harness runs the tach and has a 12v key on wire, and the larger round plug runs the TPS and A/C switches. On the 94 harness, the small plug runs the TPS and the larger plug does the rest. Thats why I was getting 12v to the TPS
I never would have thought this would be. The connectors are the same with the same amount of pins and the pins were in the same location in the plug. I spent two days screwing with this stuff, without tearing the loom off, I dont know if I would have figured it out.
So if anyone is ever swapping a newer motor... use the original harness to the truck for this. Only modification, was to use a heat shrink adhesive lined butt connector to hook up the key on power wire to the wire from the alternator. It was a green with a red stripe
Senior User
Joined: Feb 2004
Posts: 379
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From: Delavan, IL
I'm having the same problem, but no engine swap. Replaced the tach sensor and ECM relay already. I checked all of the fuses as well, and made sure the plugs were all connected. Shows cranking RPM, but nothing once it fires. Suggestions?
New User
Joined: May 2007
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I'm having the same issue as well. Tach sensor is new/good, TPS is new/good. I'm only getting .4v to the TPS though and from what I've read the TPS gets it's voltage directly from the TCM so to me it sounds like a bad TCM. 
I can only adjust my TPS from .1v to .38 at WOT. Time for a XF swap I suppose once the E4OD kills itself...
I can only adjust my TPS from .1v to .38 at WOT. Time for a XF swap I suppose once the E4OD kills itself...
Fleet Owner
Joined: Jul 2006
Posts: 20,347
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From: Mi'kma'ki
I'm having the same issue as well. Tach sensor is new/good, TPS is new/good. I'm only getting .4v to the TPS though and from what I've read the TPS gets it's voltage directly from the TCM so to me it sounds like a bad TCM. I can only adjust my TPS from .1v to .38 at WOT. Time for a XF swap I suppose once the E4OD kills itself...
I can only adjust my TPS from .1v to .38 at WOT. Time for a XF swap I suppose once the E4OD kills itself...
New User
Joined: May 2007
Posts: 22
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Does this E4OD use the VSS sensor like the 92+ even though it just has a mechanical speedo?
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