To test a P0688 OBD code, start by checking the vehicle’s battery and ensuring it has a proper charge, as low voltage can trigger this code. Next, inspect the engine control module (ECM) and its connectors for any signs of damage or corrosion. Use a multimeter to test the power and ground circuits to the ECM, ensuring they are functioning correctly. If these checks don't reveal issues, consider testing the ECM itself, as it may be malfunctioning.
ECM/PCM Power Relay Sense Circuit /Open
What does obd code P0740 mean
I think you are referring to the Universal OBD (or OBD2) test port. This is the plug under the dash that you plug the OBD code tester into. It may also be referred to as the 16-Pin Data Link Connector (DLC).
plug a obd 2 code reader into your car and activate it.
OBD I, but for the most part, you can use OBD II
OBD code P0304 is Cylinder Four Misfire.
The EEC TEST connection is in your engine compartment by the power distribution box ( OBD I / EEC IV )
Obd-on board diagnostic. The port is the plug the scan tool or code reader connects to.
J1850 is not a trouble code. It is a protocol that the OBD-II system uses. Trouble codes will be represented by a P before the numbers
OBD I code 67 - Neutral Drive Switch Circuit Open ( key on , engine off )
That should be the OBD I system. OBD II started in 1996.
OBD code P1127 mean Exhaust not warm enough.