The OBD-II standard specifies the type of diagnostic connector and its pinout, the
electrical signalling protocols available, and the messaging format. It also provides
a candidate list of vehicle parameters to monitor along with how to encode the data
for each. There is a pin in the connector that provides power for the scan tool
from the vehicle battery. OBD-II standardization was prompted by emissions requirements,
and though only emission-related codes and data are required to be transmitted through
it, most manufacturers have made the OBD-II Data Link Connector the only one in
the vehicle through which all systems are diagnosed and programmed. OBD-II Diagnostic
Trouble Codes are 4-digit, preceded by a letter: P for engine and transmission (powertrain),
B for body, C for chassis, and U for network.
If the OBDII is failing to communicate:
- Ensure that the vehicle has sufficient voltage. Check pin 16 for
power, It should be at 12 volts.
- Check the ground wires for the Chassis Ground,
pin 4, and the Signal Ground, pin 5