Low Audi charge

Oct. 30, 2012

Owners of 2005 and later Audi vehicles may report a discharged battery when trying to start the engine (no-start).

1. If the vehicle is equipped with Battery Energy manager (J644) or Battery Diagnostic Manager (J367), perform battery diagnosis to confirm a good or bad battery.

2. If the battery is defective, replace.

3. Determine if a draw currently exists by using an ammeter with an inductive pickup, such as the 5051B or Fluke Meter.

a. Start the engine and operate all accessories (radio, lights, heated seats, door locks, sunroof, power liftgate, etc.).

b. Shut off the engine, and open left and right doors, hood and rear lid.

c. Gain access to the fuse boxes. Zero the ammeter and attach the amp clamp to the negative battery cable. Lock the doors using the remote and observe the ammeter, which should spike briefly as the doors are closed. This will confirm that the ammeter is operating correctly. The vehicle may also provide a confirmation beep to confirm that all doors are latched.

d. After two hours, the ammeter should read under 0.040A (40mA). If the reading is above 40mA, attempt to locate the source of the excessive draw. If the vehicle does not exceed maximum sleep state current draw, perform a long term (overnight) measurement test. Record the long term measurement using MIN/MAX setting of the scan tool. If the long term measurement still does not exceed the maximum sleep rate current draw, proceed to Step 9.

4. To determine the potential source of the current draw, measure the voltage drop across the vehicle fuses using the VAS Scantool multimeter, Fluke multimeter or equivalent.

5. Using the “mV” scale on the multimeter, measure the voltage drop across fuses by placing the positive lead on one side of the fuse and the negative lead on the opposite side. Take absolute value of voltage drop (ignore negative signs) and then reference the voltage drop chart in the workshop manual to determine how much the circuit is currently consuming. Note: Due to the operation of CAN Bus communications, it is no longer possible to simply pull fuses to determine the location of a draw, as this action can result in a bus wakeup and invalidate the test.

6. Continue this process until the fuse with an inappropriate amount of draw (over 40mA) is discovered.

7. Once the fused circuit is identified, use service and wiring diagram information in ElsaWeb to identify all components on that circuit. Disconnect the components from the circuit one-by-one and allow the sleep current to stabilize after each disconnection.

8. Measure the vehicle current consumption and voltage drop across the fuse again. If the values are now within the normal range, the component causing excess draw has been identified. If the value are still too high, repeat the tests again until the component is identified.

9. If it is necessary to contact TAC for additional guidance, please compare the following information before opening a contact. If TAC assistance is not necessary, before returning the vehicle to the customer, test the battery state of charge and verify that it is above 85%. If the state of charge is below this value, charge the battery until at least 85% is achieved.

If TAC is to be notified, prepare the following information:

* How many times is this vehicle in the shop for a battery concern?

* When did the vehicle arrive?

* Was it towed in or jumped?

* What date did the customer have the concern?

* Is/was the date/time in the instrument cluster correct? If not, what was/is the date/time displayed?

* When did you begin to work on the vehicle?

* What is the battery serial number in the vehicle?

* Are there any other electrical concerns?

* Attach a full GFF Log with complete battery history data and Keep Awake readout (for vehicles equipped with J367).

* Attach pictures of the amplifier for Audi Q7, A4 Avant or A6 Avant vehicles if the amplifier shows no obvious signs of water damage.