i have a bluetooth OBD 2 scanner that i bought, hooked it up and it wont link with my blazer ( 2003 blazer ls ) but i put it in a 2005 grand marquise and it linked right up? i checked all the fuses and all my fuses are good ( even the cigar lighter fuse ) anyone else have any help on what possibly could be going wrong or what im doing wrong?

 

Can't help, except to say that my generic BT OBD2 reader works well in my 2000 Jimmy so I don't think it is a design flaw. Might want to check if the contacts in the connector look good.

 

i mean the lights light up on the bt adapter but it just wont connect to the ecu

 

anyone?

 

I seem to recall Ford & GM using different communication protocols. I would suggest trying it on another GM vehicle to see if it connects. If not, the problem is the adapter or perhaps the adapter's ability to auto-detect the communication protocol & select appropriately. It is also possible that the particular adapter requires manual selection of the OBD2 communication protocol.

If it does connect in a different GM vehicle, then you may have a problem with the wire that handles the serial communication between the PCM & the OBD2 port.

 

Different protocols sometimes use different pine in the connectors. The lights lighting up only means 2 of them are making contact.


Not only do the connector's pins need to be making contact, all the individual wires from the connector to the ECU need to be good too. This is probably where the issue lies.

 

Use a digital voltmeter to check the DLC connector:
1. Check ground continuity. Connect the positive (+) meter lead to DLC pin 4. Connect the negative (-) meter lead to the negative battery terminal. Use jumper wires as needed. Do not connect to a body or chassis ground; go directly to the battery terminal if at all possible. With the ignition on, voltage drop across the ground terminal should be 0.1 V or less. Repeat for DLC pin 5. An open circuit or high ground resistance prevents the ECM from entering diagnostic mode.

2. Check voltage on pin 2 of the DLC. The PCM transmits data on this pin. Connect the positive voltmeter lead to the class 2 serial data pin and the negative lead to either pin 4,pin 5, or a known good ground. With the ignition on, voltage on the class 2 serial data pin should be either 5 V or fluctuating between 3.5 and 5.0 V. If the circuit is open, the ECM cannot transmit data to the scan tool.