2021 AUDI A4 check engine

8W1012721BC
Trailer towing

Trailer towing
Driving with a trailer
eT e e eeu)
Your vehicle is primarily intended for transport-
ing people and luggage. However, if you drive
with a trailer, follow the technical requirements,
the operation and driving tips, and the legal reg-
ulations.
Driving with a trailer affects the vehicle's energy
usage, performance, and wear. It also requires
higher concentration from the driver.

Z\ WARNING
Do not transport any people in a trailer due to
the risk of fatal injury.
Technical requirements
Trailer hitch

Only use a trailer hitch with a removable ball
hitch mount and ball hitch. The trailer hitch must
be permitted for the vehicle, the trailer and the
permitted total weight of the trailer being
pulled. Above all, it must be securely and safely
attached to the vehicle trailer.
Never mount a trailer hitch on the bumper. The
trailer hitch must be mounted in a way that does
not impair the function of the bumper. Do not
make any changes to the exhaust system and the
brake system.
Check regularly if the trailer hitch is securely
mounted. Always follow the instructions given by
the trailer hitch manufacturer.
Trailer brakes
If the trailer has its own brake system, then fol-
low the manufacturer specifications. However,
the brake system on the trailer must never be
connected to the vehicle brake system.
Engine cooling system
Driving with a trailer means a higher load on the
engine and the cooling system. The cooling sys-
tem must be designed for additional load and
contain enough coolant > @®.
CG) Note
Longer inclines cannot be driven without a
suitable cooling system, especially if the out-
side temperatures are high. Otherwise, this
increases the risk of engine damage.
Operating instructions
Towing capacity
Your vehicle can only be operated with class 1 or
class 2 trailers.
Load distribution
Poor cargo load and distribution can negatively
impact vehicle handling. Load the trailer based
on the following criteria as much as possible:
— Store objects in the vehicle luggage compart-
ment, if possible. The vehicle should always
carry the heaviest possible load and the trailer
should have the lightest possible load.
— Distribute the load in the trailer so that the
heavy objects are as close to the axle as possi-
ble.
— Secure objects so that they do not slide.
— Utilize the maximum permitted tongue weight
if possible.
Tires
Set the tire pressure on your vehicle for a “full
load”; see the tire pressure sticker > page 245. If
necessary, also adjust the tire pressure on the
trailer according to the manufacturer's specifica-
tions.
The trailer and the vehicle should be equipped
with winter tires when driving in winter tempera-
tures.
Outside mirrors
If you cannot see the traffic behind the trailer
with the standard exterior mirrors, then you
must attach additional exterior mirrors. Adjust
them so you have a sufficient visibility behind
you.
Exterior lighting
Follow the legal regulations for lighting on your
trailer that are applicable in the country where
115
>

Trailer towing

you are operating the vehicle. Contact an author-
ized Audi dealer or authorized Audi Service Facili-
ty for more information.
Before you start driving, check all lighting equip-
ment on the trailer while it is hitched to the vehi-
cle.
The headlight range control automatically ad-
justs the light range of the headlights.
Safety chains
Make sure the safety chains are correctly applied
when pulling a trailer. The chains should hang
enough so that the trailer can drive around
curves. However, they must not touch the
ground.
@) Note
Attachments retrofitted on the vehicle may
cause damage, especially on the trailer hitch
ball head. In cases of damage, have the func-
tion checked by an authorized Audi dealer or
authorized Audi Service Facility.
@ Tips
— Block the wheels with chocks when parking
on inclines if the trailer is loaded.
— Audi recommends having the vehicle in-
spected between the inspection intervals if
you tow a trailer frequently.
— Avoid driving with a trailer during the vehi-
cle break-in period.
Driving with a trailer
Driving with a trailer requires extra caution.
Speed
Adhere to the legal speed limits. Follow the legal
regulations that are applicable in the country
where you are operating the vehicle.
As the speed increases, the driving stability of
the trailer decreases. Therefore you should not
exceed the maximum legal speed limit when
there are unfavorable road, weather, and/or wind
conditions. This especially applies when driving
downhill.
116
Hill
When you start driving uphill or downhill, trailers
may tilt or sway sooner than when driving ona
level surface. If small swaying movements have
already occurred, you can stabilize the trailer by
firmly braking immediately. Never attempt to
“straighten out” the trailer by accelerating.
Downshift before driving on hills to utilize the en-
gine braking effect > A\.
Brakes
When using a trailer with overrun brakes, first
brake gently then quickly. This reduces the risk of
jerking while braking if the trailer wheels lock up.
Engine coolant temperature
Pay attention specifically to the coolant tempera-
ture display when there are high outside temper-
atures, and when driving on long inclines
=> page 14. Shift to a higher gear in a timely man-
ner.

Z\ WARNING
Constant braking causes the brakes to over-
heat and can substantially reduce braking per-
formance, increase braking distance, or cause
complete failure of the brake system.

8W1012721BC
Checking and Filling

Checking and Filling
Fuel
Types of gasoline
The correct gasoline grade is stated on the inside
of the fuel filler door.
The vehicle is equipped with a catalytic converter
and must only be driven with unleaded gasoline.
Audi recommends using TOP TIER Detergent Gas-
oline. For additional information on TOP TIER De-
tergent Gasoline, visit www.toptiergas.com.
The individual gasoline grades are differentiated
by octane ratings. This value is given with (R
+M)/2 equating to AKI or in RON.
The headings below match the sticker in the fuel
filler door (examples):
UNLEADED FUEL ONLY MIN. (R+M)/2 87
Regular / MIN. RON 91 Regular
Use regular gasoline with minimum 87 AKI /
91 RON > ©.
Audi recommends using premium gasoline with
minimum 91 AKI / 95 RON to achieve the rated
horsepower and torque.
UNLEADED FUEL ONLY PREMIUM MIN. (R
+M)/2 91 / SUPER MIN. RON 95
Using premium gasoline with minimum 91 AKI /
95 RON is recommended.
If premium gasoline is not available, you can also
use regular gasoline 87 AKI / 91 RON. However
this does reduce the engine power slightly.
UNLEADED FUEL ONLY PREMIUM MIN. (R
+M)/2 93 / SUPER PLUS MIN. RON 98
Using premium plus gasoline with at least 93
AKI / 98 RON is recommended.
If no premium plus gasoline is available, you can
also use premium gasoline with 91 AKI /95 RON.
However this does reduce the engine power
slightly.
CG) Note
— Filling the tank just one time with leaded
fuel or other metallic additives will cause
permanent deterioration to the catalytic
converter function.
— When gasoline with an octane rating that is
too low is used, high speeds or heavy engine
load can lead to engine damage.
@ Tips
The vehicle may be filled with fuel that has a
higher octane rating than what is required by
the engine.
Gasoline mixture
Gasoline with alcohol or MTBE (Methyl-Tert-
Butyl-Ether)
You can use unleaded gasoline mixed with alco-
hol or MTBE (generally labeled as oxygenated
compounds) as long as the fuel meets the follow-
ing conditions:
Gasoline with methanol content (methyl alco-
hol or methanol)
— Anti-Knock Index is at least 87 AKI
—No more than 3% methanol
— More than 2% solvent
Gasoline with ethanol content (ethyl alcohol or
ethanol)
— Anti-Knock Index is at least 87 AKI
—No more than 15% ethanol
Gasoline with MTBE content
— Anti-Knock Index is at least 87 AKI
—No more than 15% MTBE
Gasoline adapted to the season
Many gasoline fuels are adapted to the seasons.
When the season changes, refueling at high-traf-
fic gas stations is recommended. It is more likely
that the gasoline will be suitable for the season
there.
@) Note
— Gasoline with methanol content that does
not meet the specified conditions may cause >
217

Checking and Filling

corrosion damage and damage to plastic or
rubber components in the fuel system.
— Do not use gasoline that does not meet the
specifications.
— If you are unable to find out if a specific gas-
oline mixture meets the specifications, ask
the gas station operator or their fuel suppli-
er.
— Do not use any gasoline mixture whose
composition cannot be identified.
— Audi does not assume any responsibility for
damage to the fuel system or for perform-
ance problems caused by using gasoline
mixtures different from those specified.
This type of damage also does not fall under
the New Vehicle Limited Warranty or under
the emissions control system warranty.
— If you notice a higher fuel consumption or
poor handling or performance problems due
to such gasoline mixtures, Audi recom-
mends fueling with unblended gasoline.
Gasoline additives
An important issue for many automobile manu-
facturers is combustion residue in the engine
that results from the use of certain fuels.
Although types of gasoline differ depending on
the manufacturer, there are similarities. Certain
substances in the gasoline may cause deposits in
the engine. Additives in the gasoline that should
keep the engine and fuel system clean do not all
function equally.
Audi recommends using TOP TIER Detergent Gas-
oline. For additional information on TOP TIER De-
tergent Gasoline, visit www.toptiergas.com.
If you use incorrect fuels over a long period of
time, the maximum engine performance may be
impaired by combustion residue.
@ Note
— Damage or malfunctions caused by the use
of incorrect types of gasoline are not cov-
ered by the New Vehicle Limited Warranty.
— Only gasoline additives that have been ap-
proved by Audi may be used.
218

Refueling
Messages
FA tank system: malfunction! Please contact
Service
There is a malfunction in the fuel tank system.
Drive to an authorized Audi dealer or authorized
Audi Service Facility immediately to have the
malfunction corrected.
Fueling procedure

Fig. 153 Right rear side of the vehicle: opening the fuel
filler door

Fig. 154 Fuel filler door with attached fuel cap
The fuel filler door is unlocked or locked by the
central locking system.
> Unlock the vehicle if necessary.
> Press on the left side of the fuel filler door to
open it > fig. 153.
> Unscrew the tank cap counterclockwise.
> Place the cap from above on the open fuel filler
door > fig. 154.
> Insert the fuel pump nozzle all the way into the
fuel filler neck.
> Begin fueling. Once the fuel pump nozzle turns
off the first time, the fuel tank is full. Donot =>

8W1012721BC
Checking and Filling

continue fueling, or else the expansion space in
the tank will be filled with fuel.
> After the fuel pump has switched off, wait five
seconds before removing the nozzle to allow
the rest of the fuel to finish dripping into the
fuel tank.
> Turn the fuel cap clockwise until it clicks into
place.
> Close the fuel filler door and then press on the
left side until it latches.
The correct fuel type for your vehicle can be
found on a label located on the inside of the fuel
filler door. For additional information on fuel, see
=> page 217.
For the tank capacity in your vehicle, refer to the
Technical Data > page 287.
To reduce the risk of fuel leaking out or vapors
escaping, make sure that the fuel tank is closed
correctly. Otherwise the Ey indicator light will
turn on.


ZX WARNING
Improper fueling procedures and improper
handling of fuel can lead to explosions, fires,
severe burns, and other injuries.
— Do not smoke. Keep away from open flames.
— The ignition must be switched off when re-
fueling.
— Mobile devices, radio devices, and other ra-
dio equipment should always be switched
off when refueling. Electromagnetic rays
could cause sparks and start a fire.
— If you do not insert the fuel pump nozzle all
the way into the filler tube, then fuel can
leak out. Spilled fuel can ignite and start a
fire.
— Never get into the vehicle when refueling. If
there is an exceptional situation where you
must enter the vehicle, close the door and
touch a metal surface before touching the
fuel pump nozzle again. This will reduce the
risk of electrostatic discharge that can cause
flying sparks. Sparks can start a fire when
refueling.


ZA\ WARNING
Audi does not recommend transporting fuel
containers inside the vehicle. Fuel could leak
out of the container and ignite, especially dur-
ing an accident. This can cause explosions,
fires, and injuries.
—If you must transport fuel in a fuel contain-
er, note the following:
— Always place the fuel container on the
ground before filling. Never fill the fuel
container with fuel while it is inside or on
the vehicle. Electrostatic discharge can oc-
cur while refueling and the fuel vapors
could ignite.
— When using fuel containers made of met-
al, the fuel pump nozzle must always re-
main in contact with the container to re-
duce the risk of static charge.
— Insert the fuel pump nozzle as far as pos-
sible into the filler opening while refuel-
ing.
— Follow the applicable legal regulations in
the country where you are driving when
using, storing and transporting fuel con-
tainers.
— Make sure that the fuel container meets
the industry standards, for example ANSI

or ASTM F852-86.



1) Depending on the engine and country
C) Note
— Remove fuel that has overflowed onto any
vehicle
components immediately to reduce
the risk of damage to the vehicle.
— Never drive until the fuel tank is completely
empty. The irregular supply of fuel that re-
sults from that can cause engine misfires.
Uncombusted fuel may enter the exhaust
system and increase the risk of damage to
the catalytic converter.
@) For the sake of the environment
— Do not overfill the fuel tank, or fuel could
leak out when the vehicle is warming up.
— Fuel should never enter the sewer system or
come into contact with the ground.
219
>

Checking and Filling

@ Tips
The fuel filler door on your vehicle does not
lock if you lock the vehicle from the inside us-
ing
the central locking switch.
Fuel filler door emergency release
Applies to: vehicles with manual fuel filler door release

If the central locking system malfunctions, the
fuel filler door can be unlocked manually.

Fig. 155 Right side trim panel in the luggage compart-
ment: opening the trim panel

Fig. 156 Luggage compartment: fuel filler door emergency
release
The emergency opening mechanism is located
behind the right side trim panel in the luggage
compartment.
> Open the cover in the side panel > fig. 155.
> To unlock the fuel filler door, loosen the red
loop from the retainer and then pull on the
loop carefully > fig. 1569©.
> Press on the left side of the fuel filler door to
open it > page 218, fig. 153.
@) Note
Only pull on the loop until you feel resistance.
You will not hear it release. If you continue to
220

pull, you could damage the emergency re-
lease mechanism.
Emissions control
system
General information
Z\ WARNING
The temperature of the exhaust system is
high, both when driving and after stopping
the engine.

— Never touch the exhaust tail pipes once they
have
become hot. This could result in burns.
— Do not park your vehicle over flammable
materials such as grass or leaves because
the high temperature of the emissions sys-
tem could start a fire.
— Do not apply underbody protectant in the
exhaust system area, because this increases
the risk of fire.
(er) 1 id (Rel Uae lg
Observe the safety precautions > page 220, Gen-
eral information.


The vehicle may only be driven with unleaded
gasoline, or the catalytic converter will be de-
stroyed.
Never drive until the tank is completely empty.
The irregular supply of fuel that results from that
can cause engine misfires. Uncombusted fuel
could enter the exhaust system, which could
cause overheating and damage to the catalytic
converter.
Malfunction Indicator Lamp (MIL)
If the S indicator light blinks or turns on, there
is a malfunction that is causing poor emissions
quality and that could damage the catalytic con-
verter. Drive slowly to an authorized Audi dealer
or authorized Audi Service Facility to have the
malfunction corrected.

8W1012721BC
Checking and Filling

The indicator light can also turn on if the fuel fill-
er cap is not closed correctly > page 218),
Engine compartment
General information
Special care is required if you are working in the
engine compartment
For work in the engine compartment, such as
checking and filling fluids, there is a risk of in-
jury, scalding, accidents, and burns. For this
reason, follow all the warnings and general
safety precautions provided in the following in-
formation. The engine compartment is a dan-
gerous area in the vehicle. > A.
Explanation of warnings (sticker in the engine
compartment):

Hot engine components!
@ Rotating parts!


The radiator fan can switch on at any
[2 time!

High voltage! Switch off the engine be-
5 fore coming into contact with any igni-
tion system components!



The catalytic converter can be damaged
"71 if the oil level is too high!

Always follow the instructions in the op-
Co erating manual.

ZA WARNING
— Turn the engine off.
— Switch the ignition off.
— Set the parking brake.
— Select the “P” (Park) selector lever position.
— Allow the engine to cool.
— Keep children away from the engine com-
partment.
— Never spill fluids on a hot engine. These flu-
ids (such as the freeze protection contained
in the coolant) can catch fire.
— Avoid short circuits in the electrical system.
— Never reach into the radiator fan. The fan is

temperature-controlled and can turn on
suddenly, even when the ignition is switched
off.
— Never open the hood when there is steam or
coolant escaping from the engine compart-
ment, because there is a risk that you could
be burned. Wait until no steam or coolant is
escaping.
— The cap on the coolant expansion tank must
never be opened when the coolant is hot.
The cooling system is under pressure. There
is a risk of burns
—To protect your face, hands, and arms from
hot steam or coolant, cover the cap with a
thick cloth when opening.
— Do not remove the engine cover under any
circumstances. This increases the risk of
burns.
— Due to the risk of electric shock, never touch
the ignition cable or other components in
the electronic high-voltage ignition system
when the engine is running or is starting.
— If a gear is engaged while the vehicle is sta-
tionary and the engine is running, do not
press the accelerator pedal inadvertently.
Pressing the accelerator pedal will cause the
vehicle to move, and this could result in an
accident.
— If inspections or repairs must be performed
while the engine is running, moving compo-
nents (such as the ribbed belt, generator,
and radiator fan) pose an additional risk.
— Set the parking brake first and select the
“P” (Park) selector lever position.
— Always make sure that no parts of the
body, jewelry, ties, loose clothing, and
long hair can be caught in moving engine
components. Before any work, always re-
move any jewelry and/or ties, tie back long
hair, and make sure all clothing fits close
to the body to reduce the risk of anything
becoming caught in engine components.
— Pay attention to the following warnings list-
ed when work on the fuel system or on the
electrical equipment is required.
— Do not smoke.


1) Depending on the engine and country
221

Checking and Filling


— Never work near open flames.
— Always have a working fire extinguisher
nearby.
— All work on the battery or electrical system
in your vehicle can result in injuries, chemi-
cal burns, accidents, or burns. Because of
this, all work must be performed only by an
authorized Audi dealer or authorized Audi
Service Facility.
— Limit your exposure to exhaust and chemi-
cals to as short a time as possible.

Z\ WARNING
California Proposition 65 Warning:
— Engine exhaust, some of its constituents,
and certain vehicle components contain or
emit chemicals known to the State of Cali-
fornia to cause cancer and birth defects and
reproductive harm. In addition, certain flu-
ids contained in vehicles and certain prod-
ucts of component wear contain or emit
chemicals known to the State of California
to cause cancer and birth defects or other
reproductive harm.
— Battery posts, terminals and related acces-
sories contain lead and lead compounds,
chemicals known to the State of California
to cause cancer and reproductive harms.
Wash hands after handling.



O Note
When filling fluids, be sure not to add any flu-
ids to the wrong reservoirs. Otherwise severe
malfunctions and engine damage will occur.
@ For the sake of the environment
You should regularly check the ground under
your vehicle in order to detect leaks quickly. If
there are visible spots from oil or other fluids,
bring your vehicle to an authorized Audi deal-
er or authorized Audi Service Facility to be
checked.

D_ The & symbol is not available in all countries.
222

Opening and closing the hood
The hood is released from inside the vehicle.

Fig. 158 Unlocked hood: lever
Make sure the wiper arms are not raised up from
the windshield. Otherwise the paint could be
damaged.
Opening the hood
> With the door open, pull the lever >) below
the instrument panel in the direction of the ar-
row > fig. 157.
>» Raise the hood slightly > page 221.
> Press the lever > fig. 158 in the direction of the
arrow. This releases the hooks.
> Open the hood.
Closing the hood
> Push the hood down until you override the
force of the struts.
> Let the hood fall lightly into the latch. Do not
press itin. > AX.
Messages
B Warning! Hood is not locked. Stop vehicle
and check the lock