The functions that finish a repair

WHAT IT DOES

Opens and closes the ABS solenoids in sequence while you bleed, so air trapped inside the modulator is pushed out rather than left sitting in it.

WHEN YOU RUN IT

After any brake job that let air into the system, and always after replacing an ABS pump or a master cylinder. A conventional bleed cannot reach inside the block.

WHICH VEHICLES

Anything with ABS, which on newer vehicles is everything. The pedal that stays soft after a textbook bleed is usually this.

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WHAT IT DOES

Runs the vehicle's own bleeding routine, holding valves and running the pump in the sequence the manufacturer specifies for that brake system.

WHEN YOU RUN IT

Any brake fluid change or component replacement on a vehicle whose manufacturer specifies a scan-tool bleed rather than a manual one.

WHICH VEHICLES

Where the record holds it. Not every vehicle needs a guided bleed, and the check tells you whether yours does.

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WHAT IT DOES

Relearns the closed and fully open positions of an electronic throttle body, so idle control and pedal response are calculated from the correct baseline.

WHEN YOU RUN IT

After cleaning or replacing a throttle body, and when a vehicle idles high, hunts or hesitates off idle after the battery has been disconnected.

WHICH VEHICLES

Anything with a drive-by-wire throttle, which is effectively every car sold since the last emissions step. Cable throttles have nothing to relearn.

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WHAT IT DOES

Stores the correction code printed on each injector against the correct cylinder, so the engine management compensates for the manufacturing tolerance of that specific injector.

WHEN YOU RUN IT

Immediately after replacing one or more injectors. Skip it and the engine runs rough, smokes, and can throw fuel-trim faults even though the parts are new.

WHICH VEHICLES

Common-rail diesel engines. It is not the same thing as ECU programming, and it does not apply to petrol port injection.

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WHAT IT DOES

Clears the learned shift and clutch engagement values so the transmission relearns them against the current state of the clutch pack or the actuator.

WHEN YOU RUN IT

After a clutch or gearbox repair, or when an automatic or AMT shifts harshly and no mechanical fault is present.

WHICH VEHICLES

Automatics, AMTs and dual-clutch gearboxes. A manual transmission has nothing to adapt.

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WHAT IT DOES

Resets the interval counter the vehicle uses to decide when the next service is due, so the wrench or SERVICE lamp goes out and the countdown starts again from zero.

WHEN YOU RUN IT

Every oil and filter change. Without it the vehicle keeps counting from the last reset and the reminder stays on the cluster whatever you did to the engine.

WHICH VEHICLES

Vehicles with an electronic service reminder. The oldest cars have a mechanical reminder and nothing to reset, so the function does not appear for them.

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• Bikes

WHAT IT DOES

Sets the zero point of the steering angle sensor, so stability control, traction control and any lane system know the true straight-ahead position.

WHEN YOU RUN IT

After a wheel alignment, a steering rack or column replacement, or when the stability lamp is on with a steering-angle fault stored.

WHICH VEHICLES

Vehicles with electronic stability control. A car without ESC has no steering angle sensor to zero.

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