Electrical and Electronic Systems Flashcards

What is a TPMS relearn procedure?

Answer: Resetting the tire pressure monitoring system after tire rotation or sensor replacement to match sensor IDs to wheel positions

After tire rotation, sensor replacement, or in some cases tire inflation adjustment, the TPMS must relearn which sensor ID corresponds to which wheel position so it can alert the driver to the correct tire.

What does a scope pattern showing a gradually rising voltage from 0.1V to 4.9V on a coolant temperature sensor indicate?

Answer: A properly functioning NTC thermistor sensor as the engine cools

NTC (Negative Temperature Coefficient) thermistors decrease in resistance as temperature rises. In a voltage divider circuit, this causes the signal voltage to drop as the engine warms up. A rising voltage indicates the engine is cooling.

What safety precaution must be observed when working on hybrid vehicle high-voltage systems?

Answer: Follow manufacturer lockout/tagout procedures including removing the service disconnect and wearing Class 0 lineman's gloves

Hybrid vehicles contain high-voltage batteries (typically 200-400V+) that can cause fatal electrocution. Proper procedures include disabling the high-voltage system via the service disconnect, waiting the specified time for capacitors to discharge, and wearing rated insulating gloves.

A vehicle has a no-crank condition. The battery tests good and the connections are clean. A voltage check at the starter solenoid S terminal shows 0V when the key is in the crank position. What is the most likely cause?

Answer: An open circuit in the starter control circuit (ignition switch, neutral safety switch, relay, or wiring)

Zero volts at the S terminal means the control signal is not reaching the solenoid. The problem lies in the control circuit — the ignition switch, neutral safety/clutch switch, starter relay, or the wiring between them.

What is the function of the mass airflow (MAF) sensor?

Answer: To measure the volume and density of air entering the engine for fuel calculation

The MAF sensor measures the mass (volume and density) of air entering the engine, typically using a heated wire or film element. The ECM uses this data as the primary input for calculating fuel injection duration.

What is the maximum acceptable voltage drop on the ground side of a starter motor circuit during cranking?

Answer: 0.2 volts

The maximum acceptable voltage drop on the ground side of the starter circuit is 0.2V. Anything higher indicates excessive resistance in the ground cable or connections, which reduces cranking performance.