OBD1 Port not functioning
Thread Starter
Heel & Toe
Joined: Jun 2023
Posts: 21
Likes: 5
From: Colorado
OBD1 Port not functioning
I am having trouble with getting my obd1 port to show codes. I had used a paper clip before to short the pins to get error codes to flash but recently it has stopped working. I also have a aldl data logging cable that I cannot get to connect either. When testing the 2 pins I got a voltage of about 5.
Melting Slicks
Joined: Aug 2003
Posts: 3,389
Likes: 391
From: Lakeville MI
What year car are we talking about?
For 86-89 cars: Open circuit voltage on Pin B should be 5 volts and near zero when shorted to ground (Pin A). You need a 10k resistor across pins A & B (which should pull down the Pin B voltage to about 2.5 volts) in order to initiate ALDL scan data, otherwise the ecm will be sending data to the dash. What is the resistance of your paperclip? Check to be sure that Pin A is really grounded.
Here's a log showing Pin B voltage (which was added to the datastream for testing purposes) with/without 10 k resistor: https://datazap.me/u/tequilaboy/aldl...rk=232-252-273
For 86-89 cars: Open circuit voltage on Pin B should be 5 volts and near zero when shorted to ground (Pin A). You need a 10k resistor across pins A & B (which should pull down the Pin B voltage to about 2.5 volts) in order to initiate ALDL scan data, otherwise the ecm will be sending data to the dash. What is the resistance of your paperclip? Check to be sure that Pin A is really grounded.
Here's a log showing Pin B voltage (which was added to the datastream for testing purposes) with/without 10 k resistor: https://datazap.me/u/tequilaboy/aldl...rk=232-252-273
Thread Starter
Heel & Toe
Joined: Jun 2023
Posts: 21
Likes: 5
From: Colorado
What year car are we talking about?
For 86-89 cars: Open circuit voltage on Pin B should be 5 volts and near zero when shorted to ground (Pin A). You need a 10k resistor across pins A & B (which should pull down the Pin B voltage to about 2.5 volts) in order to initiate ALDL scan data, otherwise the ecm will be sending data to the dash. What is the resistance of your paperclip? Check to be sure that Pin A is really grounded.
Here's a log showing Pin B voltage (which was added to the datastream for testing purposes) with/without 10 k resistor: https://datazap.me/u/tequilaboy/aldl...rk=232-252-273
For 86-89 cars: Open circuit voltage on Pin B should be 5 volts and near zero when shorted to ground (Pin A). You need a 10k resistor across pins A & B (which should pull down the Pin B voltage to about 2.5 volts) in order to initiate ALDL scan data, otherwise the ecm will be sending data to the dash. What is the resistance of your paperclip? Check to be sure that Pin A is really grounded.
Here's a log showing Pin B voltage (which was added to the datastream for testing purposes) with/without 10 k resistor: https://datazap.me/u/tequilaboy/aldl...rk=232-252-273
