ASE A6 key terms

Measuring the voltage lost across a cable, connection, switch or ground while current is flowing. Roughly 0.1 volt per connection, or about 0.5 volt total on a feed or ground path, is the usual limit before resistance is called excessive.

Current a vehicle keeps drawing from the battery after the ignition is off and all modules have gone to sleep. Measured in milliamps with a clamp or meter in series, it is the cause of repeat no-start complaints.

An unintended path between a circuit's power side and chassis ground. It usually blows a fuse, or it can keep a load energized when the switch is off, depending on where the contact occurs.

A break anywhere in the current path, such as a cut wire, backed-out terminal, failed switch contact or blown fuse. No current flows and an ohmmeter reads infinite resistance across the break.

A corroded, loose or undersized terminal or ground that limits current without blowing a fuse. It shows up as dim lamps, slow cranking, sensor errors or a voltage drop that grows as load increases.

A handheld test instrument that measures volts, ohms and amps, usually with autoranging plus min/max record, continuity and diode-check functions. It is the basic tool for nearly every electrical diagnostic procedure.

A clamp-on probe that reads current by sensing the magnetic field around a conductor. It lets a technician measure starter, alternator or parasitic current without opening the circuit.

An electromagnetic or solid-state switch that lets a small control current from a switch or module operate a high-current load such as a horn, cooling fan or fuel pump.

Rapid switching of a circuit on and off to control the average voltage delivered. It is used for lamp dimming, fan and motor speed control, and proportional solenoid control.

The spring grip a female terminal applies to its mating pin. Weak tension causes intermittent high resistance; it is checked by drag testing with a matching pin or gauge.

The amps a battery can deliver for 30 seconds at 0 degrees Fahrenheit while staying at or above 7.2 volts. It is the main rating used to compare starting batteries and match a replacement.

A quick battery test that applies a small signal and measures how well the plates conduct it, estimating cranking capacity and state of health. It does not require a full discharge load test.

Battery voltage measured at rest with no load applied. Roughly 12.6 volts means fully charged and about 12.2 volts means half charged, making it a quick state-of-charge check.

A falsely high voltage that remains on the plates just after charging or jump starting. It is removed by applying a brief load, such as headlamps for a few minutes, before testing or checking state of charge.

Hard lead sulfate crystals that form on the plates of a battery left discharged or sitting unused. It reduces capacity and cranking power and often cannot be reversed by normal charging.

A device connected at the diagnostic link or a power port that keeps module memory, radio presets and learned values alive while the battery is disconnected for service.

Resetting the battery management system when a new battery is installed so the charging strategy and learned capacity start fresh. Many vehicles with smart charging will not charge correctly without it.

An electromagnetic switch mounted on the starter that pushes the drive gear into mesh and closes a heavy contact to feed the motor. A clicking starter usually points to low control current or a bad solenoid.

A switch that blocks cranking unless the transmission is in Park or Neutral, or the clutch pedal is depressed on a manual. It sits in series with the starter control circuit.

Measuring starter current draw while the engine cranks, using an inductive clamp. Higher-than-normal draw suggests a seized engine or dragging starter; low draw suggests resistance in the cables or a worn starter.

The pinion gear and overrunning clutch assembly that the solenoid shoves into the flywheel ring gear. The clutch slips once the engine starts so the starter is not spun by the engine.

The diode pack inside an alternator that converts stator AC output into DC. A failed diode reduces output and leaves AC ripple on the charging voltage.

The circuit that controls alternator field current to hold charging voltage at its target set point, usually about 13.5 to 15 volts. It is normally built into the alternator or controlled by the PCM.

Measuring AC volts at the battery with the charging system loaded. Excessive ripple, often over about half a volt AC, points to a bad diode or stator fault.

A small sense wire that lets the regulator read actual battery voltage instead of alternator output voltage. It compensates for drop in the output cable so the battery receives the intended charge.

Loading the charging system and measuring alternator amperage with a clamp or carbon pile while watching voltage at the battery. Output is compared against the alternator's rating to judge condition.

A high-intensity discharge lamp that uses a ballast to strike and maintain an arc between electrodes. It produces bright light and uses very high starting voltage, so handling precautions apply.

A light-emitting diode lamp that draws little current and lasts long, but only works in one polarity and may need a driver or pulse-width-modulated feed to dim or avoid flicker.

The steering column stalk assembly that operates turn signals, hazards, wipers and often headlamp dimming and flash-to-pass. Faulty contacts are a common cause of lighting complaints.

The module or relay, frequently controlled by the body module, that pulses the turn and hazard lamps. No flash, fast flash or one-sided operation narrows diagnosis to bulbs, wiring or the flasher itself.

An instrument panel gauge driven by a small stepper motor commanded by the cluster electronics. A stuck, dead or incorrectly parked needle often means a failed stepper or cluster logic.

A variable-resistance sensor, such as a fuel level or oil pressure sender, that converts a physical value into an electrical signal for a gauge, cluster or control module.

The dash display that shows warnings, trip data and system messages. Incorrect or missing messages can come from the cluster, the module supplying the data, or the network between them.

The module that runs body functions such as lighting, locks, windows, wipers and security, and often acts as a relay driver and network gateway for other systems.

A two-wire differential serial network using CAN high and CAN low that lets modules share data. A shorted or open bus can disable many unrelated systems at the same time.

A single-wire, low-speed serial network used for local devices such as door switches, mirrors, seat modules and sensors. It normally operates as a subordinate of a CAN master module.

A system in which a fob transmits a coded radio signal to a receiver so the body module can lock or unlock doors, open the trunk or permit starting after the code is validated.

The mechanical assembly, using a cable, scissor or lift arm, that moves the door glass. Slow movement, grinding or a glass that drops usually means a worn regulator or motor.