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P0785, P0783, P1860, Tranny or Ignition switch???


PedroJ
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  • 2 months later...
On 9/16/2017 at 8:19 AM, Motor City Rick said:

Go to" Ign0" fuse (10 amp). Measure the available voltage on both sides of that fuse. Is it the same as battery voltage? If yes, move on. If no, find high resistance back to the battery

 

Now disconnect the ECM (ignition off), to keep things simple, test all pink wires for battery voltage on the ECM connectors.

 

If any pink wire has no voltage, go check both sides of the fuses in the power distribution center (under the hood) and the fuse panel in the dash, check for blown fuse(s).

 

Now I need you to focus on checking for battery voltage with pin # 75 (pink wire on ECM connector), that feeds the "E" pin down by the transmission.

 

Is there battery voltage? If yes, that is good, now remove the trans connector with terminal "E" and measure for battery voltage to ground. Is there battery voltage?

 

If yes, available electrical power (battery voltage) is available to the transmission.

 

If no, high resistance issue back to "Ign0" fuse.

 

Check pin # 63 also (pink wire) on ECM connector. Is there battery voltage? If yes, move to terminal "E" on the trans connector with the trans connector disconnected. Measure voltage to ground, is there battery voltage???

 

If yes, available electrical power is available to the transmission.

If no, high resistance is in the circuit back to the power junction point.

 

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when you say "power junction point" do you mean the engine fuse block? I am having the same problem as Pedro and I have narrowed it down to the fuse block. The E wire ties to the wire that goes to blue 75 on the ecm harness, a pink wire comes from IGN 0 , from the dash fuse block, and plugs in next to them , no fuse no nothing on top side of fuse block. I assume the buss wires transfer power from one to the other, but nothing in my case. Is this what i need to replace? thanks

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