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Discussion Starter · #1 ·
Some years back I had the ECM out and saw the code screw drives a potentiometer. The stop if ever there was one is broken off and the screw goes 360°. I had the ECM out to try and fix the stop but failed and frequently lose my place on the rotation when reading codes.

I bought an adapter and a bluetooth sender to read codes but no good as it's not OBD2.

I want to be able to go into code reading mode and code erase mode from the 14 pin connector.

What I'll likely have to do is, with the battery disconnected, take out the ECM and set the screw to max resistance. The potentiometer is seemingly an inexpensive approach to debouncing the signal. The center wipe arm of the pot when at max (or at min, I'll check when I have it out) is the normal state but to read codes it's brought to ground (or from ground to higher voltage). A toggle switch not debounced would bounce when switched and make problems. So, first setting the pot to normal state and adding clip leads to max min and center, closing and putting back, I can buzz each clip lead to find if there's common at the gray 14 pin OBD connector. Knowing those pinouts I can whip up a debounce with a couple of nand gates and if normal is high, drive a open collector comparitor to change the wipe arm state from high to low. I can put the circuit on perf board with wirewrap pins as contacts to be placed in the 14 pin connector. Momentary pushbutton to change the code state from normal to output codes and read the flashing CEL. Hold the momentary for a long push to reset the codes.

If anyone already has the pinouts on the gray 14 pin connector that correspond to the low, high and center of the pot, I'd appreciate knowing so I need not pull the ECM again.

Thanks
 

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Discussion Starter · #2 ·
Of course if they have the wipe arm output buffered and the connection from the gray 14 pin connector buffered as well, looking for continuity will fail.
 

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Discussion Starter · #3 · (Edited)
I'm going to guess the inputs are likely buffered which would make looking for continuity between the gray connector and pot terminals a no go.

Tacking on 28 gauge single strand wires to the pot and bringing the three out as a twisted bundle to a debounced momentary circuit might work.

Or even a dumb attempt, a clip lead to ground with a 1k resistor, ignition on, then touching each of the gray connector terminals to see if contact with any would shift to code output on the CEL. But this wouldn't be a clean signal and the multiple spikes might erase any code but would possibly identify the input of interest.
 

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Discussion Starter · #4 ·
Looking at online images of Consult gray connector pinouts, most show connections to 1,2, 7,8,9 but some show 1,2,6,7,8,9. Mine has connections to 1,2,4,7,8,9. The oddball to pin 4 is a purple wire.
 

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Discussion Starter · #5 ·
Doesn't look like touching the purple wire with a 1k to ground will do anything worthwhile. And to get codes out would need the correct signals on the purple or a data line so that out without an expensive consult. Next to improve convenience of code reading or reset will be to take out the ECM, and run test wires out, put it back in and run tests. One might be to take a pot 10x the value of the screw pot and run parallel lines but putting the pot somewhere accessible.
 

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Discussion Starter · #6 ·
Okay, only 2 wires connected to the pot, bottom and center. Neither is common with the computer case. With screw turned CCW to normal running there is zero resistance, turning the screw ~330°CW brings the resistance to 54K ohms. So, to bring the function out, I'll have to interrupt one of the two wire.
 

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Discussion Starter · #7 ·
Brought a twisted pair out, the twisted pair interrupting a wire to the pot. Twenty eight AWG, a few feet long. Not having a normally closed push button, I do have a NO microswitch I'm using in its stead. Across these NO contacts are the wires, a 56k quarter watt resistor, and a 1uf cap. The ECM pot set for normal running and taped closed. Ignition on, engine off, CEL lighted, I press the microswitch for 2 seconds and release. Codes 5-5 flash. Press the microswitch for another 2 seconds and the CEL goes to a steady on. Must run a while to set a code - damage the rear O2 sensor so I know it will set, then I'll try it again knowing there's a code just to make sure the simplistic debounce isn't losing codes somehow. Then I must cook up something to protect the switch. Don't want it accidentally getting pressed while driving. Might put the switch in the fuse box access.
 

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Discussion Starter · #8 ·
Works fine. Drove to store and set code. Checked code, 7-7, then cleared. Now to replace the damaged rear O2 sensor.
 

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Discussion Starter · #9 ·
Okay, I'm surprised. Taking the cover off to look for good mounting spots, I find that not only do I have the 14 pin gray OBD connector but underneath pointing down is the triangle OBD2 connector. Will have to look into that's functionality.
 

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Discussion Starter · #10 ·
Looking at online images of Consult gray connector pinouts, most show connections to 1,2, 7,8,9 but some show 1,2,6,7,8,9. Mine has connections to 1,2,4,7,8,9. The oddball to pin 4 is a purple wire.
So, I looked again as I found the trapezoid connector underneath. I had been working with the notion that the gray 14 pin OBD1 connector was what I should have been using with a code reader. Having seen the OBD1 connector right there in the fuse box I looked no further. Now that I know the trapezoid OBD connector is there, what is the gray rectangle 14 pin for? It has the non-regular placement of a purple wire to pin 4 and none to pin 6. Could this connector be for something else like the airbags or transmission?
 
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