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86-95 Trucks & 4Runners 2nd/3rd gen pickups, and 1st/2nd gen 4Runners with IFS

OBD 1 Diag port reader

Old 01-02-2019, 01:54 PM
  #41  
RJR
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You may also have to remove the 13K resistor. The previous guy I worked with a couple of weeks ago had to do that to get good data. Seems different serial adapters need more or less pull-up to interface properly with the diag port.

If you get a chance post a screen shot of what you are currently getting for numbers, and the conditions under which you get them. (engine running or not, engine stopped with accelerator floored, etc.) I might be able to suggest further tweaks.
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Old 01-05-2019, 09:07 PM
  #42  
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I constructed another cable using a female db9 but still getting incorrect figures. tried it with both no pull up and the 13k. Would a 5k resistor be worth trying?. Both pics below are at idle

No pull up


Pull up
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Old 01-06-2019, 06:00 PM
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RJR
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Thanks for the screen shots. The data in the second shot, with the 13K resistor in place, is consistent with most of the bits being "1". That indicates that the 13K is pulling up the data line too hard, so leave it removed for now. Putting in a 5K pullup would make things even worse.

I have a couple more questions:
1) When connected to the 4runner, are you running "ToyotaDiagTestMode.exe" or "ToyotaDiag.exe". You need to be running the second one to get valid data.
2) With the 13K removed, are the readings steady, or do they fluctuate?
3) Can you send a couple of screen shots with the key "ON" but the engine not running? One with the accelerator pedal at idle, and another with the accelerator pedal fully depressed. That will indicate how the TPS is being read. Having the engine not running will remove ignition noise from the system.

The data in the first screen shot looks like either you are getting noise, or the program is not syncing properly with the data stream. That would be the case if you were running "ToyotaDiagTestMode.exe" instead of "ToyotaDiag.exe".
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