2021 AUDI A4 check engine light

Checking and Filling


accident. Do not continue driving. See an au-
thorized Audi dealer or authorized Audi
Service Facility for assistance.
— If the brake fluid is old, bubbles may form in
the brake system during heavy braking. This
could impair braking performance and driv-
ing safety, which increases the risk of an ac-
cident.
— The brake fluid in your vehicle must meet
the standard VW 501 14 and is available at
an authorized Audi dealer or authorized
Audi Service Facility. If this brake fluid is not
available, another high-grade brake fluid of
equivalent quality may be used, and it must
meet the U.S. Federal Motor Vehicle Stand-
ard (FMVSS) 116 DOT 4, Class 6.

Switch off all electrical equipment that is not
needed. If necessary, some equipment will be
switched off automatically. Vehicle functions or
driving stability may be limited. Drive to an au-
thorized Audi dealer or authorized Audi Service
Facility immediately.
z= Electrical system: low battery charge. Bat-
tery
will be charged while driving
The starting ability may be impaired.
If this message turns off after a little while, the
vehicle battery has charged enough while driving.
If this message does not turn off, drive immedi-
ately to an authorized Audi dealer or authorized
Audi Service Facility.

@) Note
— If the brake fluid level is above the MAX
marking, brake fluid may leak out over the
edge of the reservoir and result in damage
to the vehicle.
— Do not allow any brake fluid to come into
contact with the vehicle paint, because it
will corrode the paint.
Electrical system
If the = / B or = indicator light turns on,
there is a malfunction in the power supply, the
battery, or the vehicle electrical system.
mz / B Electrical system: malfunction! Safely
stop vehicle
Do not continue driving and switch the ignition
off > A\. See an authorized Audi dealer or author-
ized Audi Service Facility for assistance.
= Electrical system: malfunction! Restart not
possible. Please contact Service
If you switch the ignition off, you will not be able
to restart the vehicle. Vehicle functions or driving
stability may be limited. Drive to an authorized
Audi dealer or authorized Audi Service Facility im-
mediately.
= Electrical system: malfunction! Please con-
tact Service
230
ZA\ WARNING
When there is an electrical system malfunc-
tion, vehicle functions may not work and driv-
ing stability may be limited, which increases
the risk of an accident. Do not continue driv-
ing and switch the ignition off. See an author-
ized Audi dealer or authorized Audi Service Fa-
cility for assistance.

Battery
ela lame (Tem eeecela)
Because of the complex power supply, all work on
batteries such as disconnecting, replacing, etc.,
should only be performed by an authorized Audi
dealer or authorized Audi Service Facility > A\.
Multiple batteries with different technologies
may be installed in your vehicle:
— Vehicle battery (for example, for starting the
engine, basic power supply) > page 231, 12
Volt vehicle battery or > page 232, Other bat-
tery types
— Auxiliary battery (for example, for recuperation
or optional equipment) > page 232, Other bat-
tery types
Not running the vehicle for long periods of
time
The battery will gradually drain if the vehicle
does not run for long periods of time. To ensure >

8W1012721BC
Checking and Filling

that the vehicle can still be started, the electrical
equipment will be limited or switched off. Some
convenience functions, such as interior lighting
or power seat adjustment, may not be available
under certain circumstances. The convenience
functions will be available again when you start
the
engine.
Even when electrical equipment is switched off,
the equipment can still drain the battery if the
vehicle is not driven for Long periods of time.
Deep draining results in a chemical reaction that
destroys the inside of the battery. The battery
must be charged every month to prevent this
= page 232. Contact an authorized Audi dealer or
authorized Audi Service Facility for more infor-
mation.
Winter operation
Cold weather places an especially high load on
the 12 Volt vehicle battery. Have the battery
checked by an authorized Audi dealer or author-
ized Audi Service Facility before cold weather be-
gins.
so that it will not be destroyed by “freezing”
=> page 232, Charging the 12 Volt vehicle
battery.
— There are electrical components under the
cargo floor behind a trim panel that warm
up during operation. To reduce the risk of
the components overheating, do not store
objects such as blankets under the cargo
floor. If the components overheat, they will
switch off temporarily. This will be indicated
by a message that will be displayed in the
instrument cluster until the temperature re-
turns to normal.
12 Volt vehicle battery
Explanation of warnings:
Always wear eye protection.

forbidden.

ZA WARNING
— 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.
— Never connect a charging cable or jump
start cable directly to the 12 Volt vehicle
battery. Only use the connections in the en-
gine compartment > page 232.

ZA WARNING
California Proposition 65 Warning:
— 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.

@) Note
— If the vehicle will be parked for long periods
of time, protect the battery against the cold
A highly explosive mixture of gases can
form when charging batteries.

Always keep children away from battery
acid and the battery.
Battery acid is highly corrosive. Always
wear protective gloves and eye protection.
® Fire, sparks, open flame, and smoking are

@/ | Always follow the instructions in the oper-
(QO | ating manual.

@) For the sake of the environment

“© % Lead-acid batteries must be disposed of
using methods that will not harm the environ-
ment. Do not dispose of them in household
trash. They contain harmful substances, such
as sulfuric acid and lead, and also recyclable
raw materials. Contact an authorized Audi
dealer or authorized Audi Service Facility for
more information.
231

8W1012721BC
Checking and Filling


— A highly explosive mixture of gases can form
when charging batteries. Only charge the
battery in well-ventilated areas.
— A drained battery can freeze at tempera-
tures around 32 °F (0 °C). Do not charge or
use a frozen or thawed battery. If ice forms,
the battery housing can crack and battery
electrolyte can leak out, which increases the
risk of an explosion and chemical burns.
Contact an authorized Audi dealer or author-
ized Audi Service Facility for more informa-
tion.
— Do not connect or disconnect the charging
cable while charging because this increases


the risk of an explosion.

@) Tips
Read all of the manufacturer's instructions
for the charger before charging the battery.
Windshield washer
system

B8W-0125



Fig. 164 Engine compartment: washer fluid reservoir cap
Observe the safety precautions > page 221, Gen-
eral information.
The windshield washer reservoir © contains the
cleaning solution for the windshield/rear win-
dow* and the headlight washer system*
> fig. 164, > page 223. The reservoir capacity
can be found in > page 287.
To reduce the risk of lime scale deposits on the
spray nozzles, use clean water with low amounts
of calcium. Always add window cleaner to the wa-
ter. When the outside temperatures are cold, an
anti-freezing agent should be added to the water
so that it does not freeze.
Messages
3 Please add washer fluid
Fill the washer fluid for the windshield washer
system and the headlight washer system* when
the ignition is switched off.
@) Note
— The concentration of anti-freezing agent
must be adjusted to the vehicle operating
conditions and the climate. A concentration
that is too high can lead to vehicle damage.
— Never add radiator anti-freeze or other addi-
tives to the washer fluid.
— Do not use a glass cleaner that contains
paint solvents, because this could damage
the paint.
Service interval display
The service interval display detects when your ve-
hicle is due for service.
The service interval display works in two stages:
— Inspection or oil change reminder: after driv-
ing acertain distance, a message appears in the
instrument cluster display each time the igni-
tion is switched on or off. The remaining dis-
tance or time is displayed briefly.
— Inspection or oil change due: if your vehicle
has reached an inspection or oil change interval
or both intervals at the same time, the mes-
sage Inspection due! or Oil change due! or Oil
change and inspection due! appears briefly af-
ter switching the ignition on or off.
Checking service intervals
You can check the remaining distance or time un-
til the next oil change or next inspection in the
Infotainment system.
Applies to MMI: Select on the home screen: VE-
HICLE > Settings & Service > Service intervals.
Resetting the indicator
An authorized Audi dealer or authorized Audi
Service Facility will reset the service interval dis-
play after performing service.
233
>

8W1012721BC
Fuses and bulbs

@) Note
If a new fuse burns out again shortly after you
have installed it, have the electrical system
checked as soon as possible by an authorized
Audi dealer or authorized Audi Service Facili-
t y.
G@) Tips
— The following table does not list fuse loca-
tions that are not used.
— Some of the equipment listed in the follow-
ing tables applies only to certain model ver-
sions or certain optional equipment.

Fig. 184 Driver's footwell (left-hand drive vehicle): fuse
panel with plastic clip
3
=f
= & a

x
Ss $ 2 8

Fig. 185 Front passenger's footwell (right-hand drive vehi-
cle): fuse panel with plastic clip


f ) (brown)
No. | Equipment

1 | Catalytic converter heating

2 | Engine components

Exhaust doors, fuel injectors, radiator in-
let, crankcase housing heating

Vacuum pump, hot water pump, NOx sen-
4 |sor, particulate sensor, biodiesel sensor,
exhaust doors

Brake light sensor

6 | Engine valves, camshaft adjustment

Heated oxygen sensors, mass airflow sen-
sor, water pump

Water pump, high pressure pump, high
8 |pressure regulator valve, temperature
valve, engine mount

Hot water pump, motor relay, 48 V drive-
train generator, 48 V water pump

10 | Oil pressure sensor, oil temperature sensor

Clutch position sensor, 48 V drivetrain
11 |generator, water pump, 12 V drivetrain
generator

12 | Engine valves, engine mount


13 | Engine cooling

273

8W1012721BC

Drive select

refer to Audi drive select.............0. 110
Drive system... 1.2... cee ee eee 101
AUdi drive Select sais s & news < ¢ says & 3 ve 110
Drive system (message) ........... eee eee 103
Driving down hills............ 00.000 eee 107
DFIVIMGJPFOGFAMM:. « wnaceos % 0 spesine 6 & axonese on mune 137
Driving through water...............0.. 108
Driving CIM: « cescues & a ssanees vw ones vv orn a 8 a 16
Driving tips
Driving through water...............-- 108
Efficient driving...............-00000- 102
Offroad GriWitG cows sc caws se pean es ewan 108
Uphill and downhill................00. 107
Driving:up Wills: « ssc s 2 wave 6 o sree wv sew 107
Dust filter
refer to Pollutant filter................. 90
DYMAMMIGIStEORIAG, cxsieos ov secre © « soneers © ¥ soaser Lill
E
EFimailss os i: cwcsan oa ncewios ow sesnin @ ononans wa wretnon 4 T/1,
Settings............. 0.00. e eee eee ee 171
EDL
refer to Electronic Differential Lock...... 113
EDR
refer to Event Data Recorder (EDR)...... 277
Efficiency ASSISE: s wes » x ows & a ews 8 6 ow 128
Predictive :comtro lin: « cxvim x 0 sensawe oo swowane 133
Electrical system ........ 2... cee eee eee 230
Electromechanical parking brake......... 106
Electronic Differential Lock.............. 113
Electronic immobilizer................5-. 38
Electronic Stabilization Control........... 113
Embedded SIM card............--.00005 174
Emergency assistance...............00. 261
Emergency braking function............. 106
Emergency call... «ccc. 2 mwa ve ewe 169,178
Emergency flashers..............--0000- 53
Emergency modéw Emergency operation
DOONS eves ov comme a a same ao omnes vv om x
Fuel filler door
Luggage compartment lid............... 43
Panoramic glass roof................005 47
Sliding/tilting sunroof...............00. 46
Emissions control system..............- 220
EnergyCOnsSUMErSi. & & sive a 2 wasn ao mare oes 16
Energy management...............0005 102
Engine
Breakingiin « sss c= cee = 2 aves ov ere a ee 101
Coolant..... 0.0... cece eee eee ee eee 227
EMe@ngenty StOpis « = ewes 5 2 sees ¢ 2 wees Fs me 95
JUMp'StARtING & vesi% « 6 war % 6 senens & ewes 268
Start/Stop system ......... 0. eee ee eee 102
Starting/Stopping:: « « seme os ews 5 wen s « 95
Engine compartment
Opening and closing the hood.......... 222
OVERVIEW cscssiic xo ciueins xo anette 6H atetaaie © ooetts 223
Safety precautions..................0. 221
Engine oil
AGQING = ex ¢ = seem « = ress « ¢ ee § pe 224
GhANGING sis «sess ss rena « waver 2» omen © 226
Checking oil level.............00-.000- 224
CONSUMPtIONs « 2 was s 2 ene x eee 5 oe 224
Indicator light « sss + «owes sw ssweenn ow vase 224
Replacement interval................. 233
Temperature display............0.e00e 15
Engine sound
Audi driveselect’s osx. < + sx » x come © ee 110
Engine Start/Stop mode
refer to Start/Stop system............. 102
Engine startsystem sce 3 5 seu o 9 was o 9 som 96
Engine stop
refer to Start/Stop system............. 102
Entry/exit. IQhtingie: + scsi as essen & © wonvme a v6 53
Entryiassistanee:: 2 coca 2s acim os eee 2 o were 65
also refer to Exit assistance............. 65
Environment
Unleaded gasoline.................00. 217
ESC
refer to Electronic Stabilization Control... 113
ESC Offroad... 2.1... eee eee ee 114
ESC Sport........... 000.000.0000 0000- 114
eSIM
refer to Embedded SIM card............ 174
Event Data Recorder (EDR).............. 277
Exit assistance .... 0.2... 0.00... e eee eee 65
Exit warning ...... 0.66... e ee ee eee eee 148
Exteriomantenna «cise oo srerw wane © aecete 165
Exterior Lighting’: = = sce «= seus © x cere = 4 seus 51
291