GM Service Manual Online
For 1990-2009 cars only
Coolant Level Switch: The scan tool displays Ok or Low. The PCM monitors the engine coolant level switch. A closed switch is displayed as On.

ECT Sensor: The scan tool displays -39° to +140° C (-38° to +284° F). The PCM monitors the voltage at the signal circuit of the engine coolant temperature sensor. The voltage is inversely proportional to the engine coolant temperature.

Engine Oil Level Switch: The scan tool displays Ok or Low. The PCM monitors the signal circuit of the engine oil level switch. A closed switch is displayed as Ok.

Engine Oil Life Remaining: The scan tool displays 0 to 100%. The PCM calculates the amount of life of the engine oil.

Engine Speed: The scan tool displays 0-9999 RPM. The PCM monitors the signal circuit of the crankshaft position (CKP) sensor.

Fuel Level Sensor: The scan tool displays 0 to 5 Volts. The PCM monitors the fuel level sensor signal circuit. A low fuel condition is displayed as low voltage.

Fuel Level Sensor Rear: The scan tool displays 0 to 5 Volts. The PCM monitors the rear fuel level sensor signal circuit. A low fuel condition is displayed as low voltage.

Fuel Tank Level Remaining: The scan tool displays Liters (Gallons). The PCM monitors the fuel level sensor signal circuit in order to calculate the amount of fuel remaining in the fuel tank.

Fuel Tank Level Remaining: The scan tool displays 0 to 100%. The PCM monitors the fuel level sensor signal circuit in order to calculate the percentage of fuel remaining in the fuel tank.

Ignition 1 Signal: The scan tool displays 0 to 25.5 Volts. The PCM monitors the voltage at the ignition 1 signal circuit.

Low Oil Lamp Command: The scan tool displays On or Off. When the PCM detects that the engine oil level is low, the PCM will command the low oil indicator ON.

MIL Command: The scan tool displays On or Off. The commanded state of the MIL indicator.

Reduced Engine Power: The scan tool displays Active or Inactive. When the throttle actuator control module (TAC) detects a malfunction in the TAC system, the TAC sends a signal to the PCM through a dedicated serial data circuit. The PCM reduces engine power and commands the reduced engine power indicator ON.

Vehicle Speed Sensor: The scan tool displays 0-255 km/h (0-155 mph). The PCM monitors the signal circuit of the vehicle speed sensor.