Failed daytime running lights, faults after a battery change and annoying TPMS warnings are among the most common electrical problems with the Audi Q5. These complaints mainly affect models built between 2009 and 2016. Some owners experience sporadic failures. Others have to deal with persistent error messages without an obvious cause. Owners often want to understand for themselves what is going on. They look for solutions within reach. This article offers concrete insights and practical starting points.
Why do daytime running lights fail on the Audi Q5?
The failure of a single daytime running light is a familiar problem. This often happens on the front right or front left. Many owners see a warning about lighting voltage appear on the dashboard, while the light itself becomes dim or goes out completely. The root cause is rarely the LED module itself, but much more often the wiring or the connectors.
The wiring around the right-hand daytime running light is prone to corrosion and loose connections. Voltage dips often occur, especially in conditions with a lot of moisture, salt and temperature fluctuations. These dips mean the module is no longer driven correctly. In some cases the fault disappears by itself after starting the car. However, the LED strip clearly remains less bright than before.
Another very common cause is a defect in the control unit itself. This module controls the supply voltage for the daytime running lights. Fluctuations in the electrical system damage the module. A characteristic sign is that the fault then stubbornly persists, even after disconnecting the battery.
‘ Many electrical systems lose their calibration or stored settings during a battery change. ’
Electrical faults after replacing the battery
Changing a battery seems like a routine job, but on the Audi Q5 it regularly triggers electrical problems. Owners report faults in the lighting, parking sensors and, in extreme cases, even CAN bus-related error messages. Many electrical systems lose their calibration or stored settings during the battery change. These problems therefore often arise immediately after the replacement.
Relays and control modules in particular behave differently after a power interruption. The Body Control Module (BCM) plays an important role here. This central component coordinates all electrical functions, from lighting to the instrument cluster. The BCM loses its power supply. After that it produces intermittent faults. However, no clear fault codes are often read out.
A practical first step is to check all fuses in the engine compartment. A blown fuse may be the result of a brief power surge during the battery change and is simple to replace. Park the car on a flat surface. Then recalibrate the adaptive systems via the menu in the car. This often helps.
TPMS faults and how to reset them
The tyre pressure monitoring system (TPMS) sometimes gives a warning without any obvious reason. Owners then see a warning light on the dashboard, even though the tyre pressure is correct. This problem often occurs in combination with other electrical faults. The BCM or the gateway module is then passing on incorrect information.
Resetting the TPMS helps in many cases. Park the car stationary on a flat surface. Check the tyre pressures. Then start the TPMS recalibration via the infotainment system or service menu. The car then needs a short drive to resynchronise the sensors.
The warning sometimes keeps coming back. In that case a sensor may be defective. It is also possible that the module which processes the TPMS data is not communicating properly with the CAN bus network. A read-out with a diagnostic computer is necessary in that case. This shows whether it is a hardware or software issue.
CAN bus problems and voltage fluctuations
The CAN bus forms the backbone of all electrical communication in the Audi Q5. This network is sometimes disrupted. As a result, unpredictable issues arise such as lights going out, non-functioning instruments or incorrect warnings. A characteristic feature is that fault codes are often not stored. Standard diagnostics therefore yield little.
Measuring the CAN lines with an oscilloscope makes it clear whether voltage fluctuations are occurring. Are there voltage fluctuations? Normally the high and low lines operate at stable voltage levels around 2.5 volts. These values sometimes deviate or fluctuate. This points to a defective connector, damaged wiring or a fault in a connected module.
Owners with aftermarket accessories such as dashcams in particular report this type of fault. Some owners install dashcams. Incorrectly connected equipment interferes with the CAN bus network. This causes sporadic failure of parking sensors, reversing cameras or headlights. Removing the dashcam or checking the power connection resolves the fault in such cases.
‘ A loaded measurement gives a more realistic picture. ’
Practical steps for self-diagnosis
You want to check for yourself where the problem lies. There are a number of steps you can take without specialist equipment. Start by visually inspecting the wiring and connectors around the headlamp where the daytime running light is failing. Look for signs of corrosion, green deposits or loose pins in the connector.
Use a multimeter. Measure the supply voltage at the connector of the LED module. Keep the plug connected while doing so. Then perform a loaded measurement. A loaded measurement gives a more realistic picture. A measurement in an unloaded state is less accurate. A voltage drop indicates problems. The cause then lies in the wiring. Another possible problem is the relay.
Also check the fuses in the fuse box under the bonnet. The car’s manual indicates which fuse belongs to which system. A blown fuse is quick and inexpensive to replace. Owners of models from 2012–2016 temporarily swap the left and right LED modules. This helps to trace the cause. If the fault moves with the module, then the module itself is the problem. If the fault stays on the same side, then the cause lies in the wiring or the relay.
Prevention and maintenance tips
Regular maintenance prevents many electrical faults. Clean the connectors of lights and sensors at least once a year. Do this especially after the winter season, when there is a lot of salt on the road. Corrosion in the connectors is one of the main causes of voltage problems.
When replacing the battery, make sure that the electrical power supply does not drop out completely. Use a memory saver. If not, connect the new battery before disconnecting the old one. This way the settings of the BCM and other modules are retained. You then avoid calibration problems.
Be careful when installing aftermarket accessories. Incorrect wiring carries risks. Connect dashcams and other devices via a voltage regulator. Incorrect wiring or overloading disrupts the CAN bus network. This leads to unexpected faults in lights and sensors.
When is professional help needed?
Some faults do not resolve with simple checks. Resets do not help either. Error messages sometimes keep returning. First check the wiring and fuses. Do the warnings persist? Then call in professional diagnostics. A specialist workshop has advanced equipment such as an oscilloscope. This workshop analyses the CAN bus signals. Defective modules can then be identified.
For faults in the BCM or the gateway module, a software update is often required. In other cases the module has to be replaced. This requires knowledge of the Audi system. Access to dealer software is also needed. Dealer repairs are generally effective. The costs can sometimes add up, especially when several modules have to be replaced.
An alternative is to make use of independent specialists. These specialists are familiar with Audi’s electrical systems. Many owners report that these workshops deliver the same quality. The hourly rate is lower. Always ask for a detailed quote. Also ask for clarity on diagnostic costs before authorising the work.
‘ The information covers all model years. ’
Discover more about the Audi Q5
The electrical faults affecting daytime running lights, TPMS and the CAN bus network are only part of what you may encounter as an owner. On the Carnews website you will find extensive information on common problems. You will also find maintenance advice and practical tips for all Audi Q5 models. The information covers all model years. Discover more on the website. Stay informed about new developments. These developments help you move forward as a car enthusiast.
Frequently asked questions
The most common electrical problems with the Audi Q5 are CAN bus/BCM faults that cause lights and instruments to fail, voltage fluctuations and faults in adaptive headlights and cameras. Specifically for the daytime running lights, the left or right LED modules often fail, usually due to problems in the wiring or connectors rather than the LED itself. Corrosion and loose connections at the headlamp plugs – especially front right – cause voltage dips and intermittent failure of the daytime running lights. Defective control modules or switches can also affect daytime running lights, parking sensors and reversing camera at the same time.
Start with a visual check: see whether the left/right daytime running light is really out, and check the wiring and plugs at the headlamp (especially front right) for corrosion, breaks or loose connections. Then check the relevant fuses in the engine bay and interior and replace any blown fuse. Use a multimeter to check whether there is voltage at the daytime running light plug when the ignition is on. If there is voltage but the module stays off, there is a good chance the LED module itself is defective and needs replacing.
The average repair costs for common electrical issues on an Audi Q5 are usually between €150 and €400, including diagnostics, labour and any repair or replacement of wiring/connectors. Specifically for problems with the daytime running lights (LED module or wiring), you should allow roughly €250 to €600 per side, depending on the brand/quality of the headlamp unit and the workshop’s hourly rate. Dealer repairs are usually at the upper end of these ranges, while independent garages tend to be at the lower end. Extra diagnostic hours for complex CAN bus or BCM faults can easily add a few hundred euros to the total cost.
Yes, as a preventive measure you can periodically check and clean the plugs and wiring of the daytime running lights (especially front right), particularly after driving on salty or wet roads, to prevent corrosion and voltage loss. Make sure all fuses in the engine compartment are intact and replace any suspect fuses in good time. Avoid poorly installed or cheap aftermarket equipment (such as dashcams) that is connected to the same power supplies or CAN bus, as these can cause faults in lights and other systems. If you have recurring or vague electrical issues, have the CAN bus and BCM lines professionally measured under load once so that emerging problems are detected early.
Other signs of an incipient electrical problem on an Audi Q5 include intermittent or dimming headlights/rear lights, parking sensors or reversing camera that sporadically stop working, and unexplained warnings in the dashboard that disappear again. Varying operation of adaptive headlights and reversing lights during cold starts can also be an indication. Respond by first checking fuses and visible wiring/connectors (especially front right) for corrosion or loose plugs and by measuring the onboard voltage. If the problem persists or multiple systems are affected at the same time, have the BCM/CAN bus professionally read out and measured under load.