Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
Serial Communications
2000 Saturn LS1 L4-2.2L VIN FSECTION Serial Communications
Scan tool operation is accomplished with bi-directional communication between the tool and the PCM. OBD II technology requires a much more sophisticated PCM than did OBD I technology. The PCM diagnostic management system not only monitors systems and components that impact emissions, but also runs active tests on these systems and components. To accommodate this expansion a Class II serial data bus is used which meets SAE J1850 specifications for serial data.
"Serial Data" refers to digital information which is transferred over a single line, one bit at a time. A "Data Bus" is an electronic pathway through which digital data travels.
Class II data, which is used on OBD II vehicles, communicates at a much faster rate. The rest voltage on a Class II bus is 0 volts and is switched high (seven volts) when communications are taking place.
OBD II requirements standardize the Data Link Connector (DLC) to use 16 pins. (All vehicle manufacturers must conform to the 16 pin DLC standard.)
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When to See a Mechanic
Stop DIY work and contact a certified mechanic immediately if any of the following apply:
- • You smell fuel, burning insulation, or see smoke.
- • Brakes feel soft, pull hard to one side, or make grinding noises.
- • The engine overheats, stalls repeatedly, or misfires under load.
- • You are missing required tools, torque specs, or safe lifting equipment.
- • You are not confident in the next step or safety outcome.