2021 Audi Start/Stop System Operation Information TSB

Audi has issued Technical Service Bulletin (TSB) 00 20 42 2045316/5 to provide comprehensive information regarding the operation of the Start/Stop system across various models. This TSB, dated October 7, 2020, supersedes previous bulletin Group 00 number 19-27 and aims to clarify the system's behavior for both owners and technicians.

The Audi Start/Stop system is designed to enhance fuel efficiency by automatically shutting off the engine when the vehicle is stationary and restarting it when the driver intends to move. However, its operation is governed by numerous factors, which can sometimes lead to perceived malfunctions.

Common Owner Concerns

Owners frequently report the following observations regarding their Audi Start/Stop system:

• The Start/Stop system does not shutdown when the driver thinks it should.
• The engine is not automatically switched off or on.
• The engine restarts from Start/Stop for reasons unknown to the driver.

How the Audi Start/Stop System Works

The Start/Stop system is an integrated feature that automatically stops and restarts the engine to reduce emissions and fuel consumption. It is important to note that if your vehicle is equipped with this system, it cannot be legally disabled. The system continuously monitors various vehicle conditions to determine when it is appropriate to engage or disengage.

Conditions for Automatic Engine Switch-Off

For the engine to automatically switch off, several conditions must be met:

• The minimum engine temperature must have been reached to ensure efficient heating and warm-up.
• The vehicle must have exceeded 10 km/h (6 mph) or 3 km/h (2 mph) for manual transmissions, and then come to a complete standstill.
• The battery's charge level must be sufficient to guarantee a successful restart.
• The defrost function must be deactivated.
• The driver must be wearing a seat belt.
• The driver door and the hood must be closed.
• The engine speed must be below 1,200 rpm.
• The diesel particulate filter (DPF) must not be in a regeneration process.
• The target HVAC temperature must have been reached.
• The road incline must be under 10 degrees.
• The steering wheel must not be turned more than 270 degrees (3/4 turn) as the vehicle comes to a standstill.
• For automatic vehicles, the brake pedal must be pressed and held as long as the Start/Stop function is to be active.
• A gear must not be selected (manual transmission only).
• The clutch must not be pressed (manual transmission only).

Why the Engine Might Not Switch Off Automatically

There are specific situations where the engine will not automatically switch off, even if some conditions are met:

• The vehicle is electrically connected with a trailer (only with factory trailer installation).
• The system was manually deactivated using the button on the center console.
• The clutch is depressed (manual transmission only).
• A gear is selected (manual transmission only).
• The brake pedal is not pressed hard enough.
• The parking aid is switched on.
• The interior temperature selected on the air conditioning system has not yet been reached.
• The charge level of the battery is too low.
• The windscreen is being defrosted.
• The steering wheel is turned more than 270 degrees.
• The vehicle is inclined too much.
• The system remains switched off if, after a battery replacement, the battery has not been adapted with Guided Functions, or if the system is still calculating the charging curve. This process typically takes about 10 start cycles.
• Too many electrical consumers are switched on.

Why the Engine Might Restart Automatically

In certain situations, the engine may automatically restart without driver involvement:

• The vehicle moves with the engine switched off and reaches a speed of more than 3 km/h (2 mph), for example, due to a slope.
• On an automatic vehicle, the selector lever position "R" is selected.
• The coolant temperature drops or rises too much.
• The vacuum in the brake servo has dropped, leading to reduced braking assistance.
• The interior temperature differs from the value selected in the air conditioning system.
• The charge level of the battery is below a certain level.

For the engine to be started deliberately after being turned off by the Start/Stop system, the clutch pedal must be pressed, or for automatic vehicles, the brakes must be released (without Auto Hold function), or the Start/Stop button is pressed (lit up).

Important Warnings

This TSB emphasizes that the Start/Stop system is complex, and many perceived issues are often normal operation or influenced by driver/passenger actions. Technicians are advised:

• Please do not replace parts without proper diagnosis.
• This TSB is informational only and not applicable to any Audi Warranty.

Diagnostic Guidance for Technicians

If a customer concern about the Audi Start/Stop system is confirmed, technicians should follow these steps:

1. Check for relevant faults and diagnose using Guided Fault Finding.
2. Utilize Guided Fault Finding 1st for effective diagnosis of the Start/Stop system.
3. If Guided Fault Finding does not resolve the concern, additional information on self-diagnosis and Start/Stop system operation is available in the attachment "Audi Start/Stop systems, Workshop Manual and instructions for analysis."

All parts and service references in TSB 00 20 42 2045316/5 are subject to change. Always consult the latest information with your Parts Department and/or ETKA, and check the Repair Manual for fastener replacement guidelines.

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Source: NHTSA ID: 10181056