1990 7.3idi E40D tach not working need help

[PreferredRI]

I have a 1990 Superduty wrecker 7.3 auto with tach not functioning and trans in limp mode. I checked all fuses, all good. I replaced tach sensor with new one made no difference, my question is does anyone have a wiring diagram so I can find what wires to test to see where I am losing signal. We will use this tow truck at a local race track to tow off wrecked race cars and it hasnt worked since we got the truck. Trying to correct it before it goes into service. Thank you.

 

[Randy Bush]

I have a complete wiring diagram for an 89, but with it in front on you it would take me some time to trace them all out. Am wondering if you don't have a bad ground on it for the tach.

 

[PreferredRI]

I am trying to find the relay and I cant seem to find it, I did find two plugs between the coolant tank and the fart can that have red ontop of the plugs, there are no relays plugged in but they look like a plug that a relay would go into.

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[trackspeeder]

EEC (TCM) relay plugs into that socket. Replace the relay, your tach and TCM should come to life.

 

[PreferredRI]

Thank you very much I will go find one and try it

 

[PreferredRI]

Thank you that fixed that issue, thanks again