Clearing ECC codes with "LED flasher unit"

67Amazon · Post by **67Amazon** » 30 May 2024, 14:09

Greetings, 1997 850 GLT (LPT) Bosch Motronic 4.4

Using a home-brew LED code reader I was able to pull multiple codes from the ECC unit, but I'm having trouble clearing the codes after reading them.
I searched the forms and was led to believe that I could clear the code after verifying that I read all the codes (twice)..
I wanted to clear the codes to see which one came right back (hard codes).
Driver side "blend door" is stuck in the "hot" position among other issues.
What is the exact procedure for resetting the ECC.
Tried holding the button down to get a "steady Light", but it just went back to showing error codes.
Using pins 13, 5, 6 on the OBD II connector.
Do all the ECC problems need to be fixed first before it will reset ??

Thanks all
Peter

Post by **Clemens** » 30 May 2024, 23:57

On OBD 1 you had to read all codes before you could reset them.
Don't think you have to fix all of them.
I wonder if unhooking the battery over night could solve that issue. It won't work for SRS lights, but I think others were able to get Rid of sporadically triggered engine lights by unhooking the battery.

Post by **jreed** » 31 May 2024, 05:41

What does your code reader circuit look like, specifically the type of LED and current-limiting resistor that you're using? Asking because I found that my original design with a high resistance (5000 Ohms) resistor worked for reading but not clearing codes. I switched the resistor to a lower value (500 Ohms) and was able to clear codes reliably.

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67Amazon · Post by **67Amazon** » 04 Jul 2024, 14:16

the LED code reader I used was borrowed from a friend. the LED has a built-in resister of undetermined value. I going to make myself another one with some part I had laying around. the resistance on the LED that I'm going to use measures around 26 ohms.
We'll see if changes test results.

Post by **jreed** » 04 Jul 2024, 16:50

I haven't tried such a low value, but it seems like it could lead to a relatively high current through the LED if I'm doing my Ohm's law calculation correctly (12V / 26 Ohms = 462mA). That might blow out the LED, depending on the maximum current rating.