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Electrical short

Pops the 15 amp main power relay, ECU, 02 Sensor as soon as key turns on.
Here is the what I have dones. Checked and cleaned grounds and battery terminals. Checked harness for short to power or ground. Isolated it to the MPR1 relay circut. Pull mpr1 relay put in fuse pull up codes. 711 LSD_1 dither 1 open or short to ground blaa blaa. What and where is a dither?
431 EST1 open or shorted to power or ground or bad spark module. Again what and where is EST1?
Have color schematic and mpr1 is green n white for 02 sensor. Red battery, red n white x2. 1 red n white goes to ECU power, other red n white goes to optional connector. I still have to find the opt connector, if used and what it feeds.
Any thoughts?
  • Posted 16 May 2018 10:57
  • By Shadetree5080
  • joined 16 May'18 - 4 messages
  • Nevada, United States
Shade
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Dither valves or also called FTV (fuel trim valve). can be found behind the vaporizer two black valves with vac lines and wiring attached. LSD refers to the style of Delco ignition system used. Check for shorts to and from the distributor, coil ect. Check also the harness which crossed over the transmission. Often this harness will wear through and short to trans.
  • Posted 18 May 2018 07:07
  • By tom_p
  • joined 21 Feb'11 - 198 messages
  • Alberta, Canada
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Fact of the week
The two internal cavities in our nose called nostrils function as separate organs. Each nostril has its own set of turbinates and olfactory receptors. The two independent organs work together through a mechanism called the nasal cycle, where one nostril is dominant for air intake while the other rests and is better at detecting scents.