Checking Standby Current
Checking standby current
Preparations for standby current measurement
General
When the vehicle sets the communication buses and the control modules in "sleep mode", power consumption drops. Factors such as whether the vehicle is locked, the alarm is on or off or whether any doors are open affect the rate at which the vehicle will reach standby power consumption. The lowest power consumption is achieved the quickest when the vehicle is locked, the alarm is on and the vehicle's doors are closed.
Note! There is a battery monitoring sensor on vehicles with the automatic start/stop of engine function and/or brake energy regeneration. It registers the vehicle's stand-by current consumption among other things. Stand-by current consumption can be readout and used for fault tracing. See VIDA/DIAGNOSTICS/VEHICLE COMMUNICATION/ECM/Advanced or VIDA/DIAGNOSTICS/VEHICLE COMMUNICATION/CEM/Advanced depending on model.
Preparations
Ensure that all lighting is switched off.
Ensure that the diagnostic tool is not connected in the vehicle.
Open the tailgate or trunk lid and bonnet and set the locks to the deadlocked position using a screwdriver for example.
Open the driver's and passenger doors and set the locks to the deadlocked position using a screwdriver for example.
Close the rear doors, remove the key and lock and alarm the vehicle. Never use reduced alarm as it then takes longer for the CAN network to continue in "sleep mode".
Wait until the vehicle has come down in standby current consumption, which can take up to 10 minutes.
Note! Do not open any doors or the test will have to be restarted from the beginning.
Continue - Connecting the measuring instrument
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Connecting the measuring instrument
General
When measuring the power consumption, it will soon become evident if there is a power consuming component in the car drawing an excessive amount of the battery capacity. If it is clear that the power consumption is greater than the specified limit values, fault trace by successive elimination.
The method for measuring the total standby current consumption is described below.
The vehicle's standby current is measured using a multimeter.
Note! If the vehicle has been run to operating temperature, check that the system relay has been activated. An activated system relay causes increased standby current consumption. This is normal under certain circumstances.
Continue - Measurement method
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Measurement method
When measuring the vehicle's total power consumption, connect the measuring instrument in series with the battery at the battery's negative pole.
Connecting the multimeter at the battery negative pole
Note! To avoid current surges that could damage the measuring instrument when the battery cable is connected, carry out the following. Never connect the measuring instrument if the engine cooling fan is in operation as this can damage the instrument.
Ensure that the multimeter is equipped with a clamp and a probe.
Check that the multimeter is set for current measurement.
Disconnect the nut on the battery cable's negative pole.
Note! Do not lift the battery cable so that the circuit is broken.
Secure the clamp on the negative pole's battery cable terminal.
Note! Check that the connections are installed correctly. If the circuit is broken, the standby current must be re-checked from the beginning
Place the end of the probe on the battery's negative pole.
Slowly lift the battery negative cable without removing the probe.
Stop when the battery negative cable hangs freely without touching the battery or the probe.
Measuring and reading off the total standby current.
Read off the standby current consumption. The total standby current should be less 25 mA.
Note! If the car is equipped with "Volvo on call" and the standby current is too high, wait 5 minutes and measure again. The "Volvo on call" system is active for short periods and then increases the short-term standby current above the normal value.
Reinstall the battery's negative cable.
Look and listen for unusual vehicle behavior. Check, for example, if a relay is hot, if it is this can indicate that current is flowing through it.
Note! Do not carry out work inside a vehicle equipped with mass movement sensors as the alarm may be triggered.
Check that the CAN network has continued in "sleep mode", see instructions. Checking Can-net's rest status Checking Can-Net's Rest Status
If the standby current is OK and the CAN network is still in "sleep mode", reset the vehicle.
Note! Do not forget to unlock the trunk lid or tailgate and doors.
If a fault is detected, fault-trace the relevant system. Otherwise continue fault tracing by successive elimination.
Continue - Fault tracing by successive elimination
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Fault tracing by successive elimination
During fault tracing by successive elimination, try to localize the problem by measuring the power consumption at the same time as removing one fuse at a time in the vehicle.
Procedure
Expose the integrated relay/fusebox in the engine compartment and the fuses in the Central electronic module (CEM).
Use the multimeter and check that the relays and fuses have the correct voltage, use the wiring diagram and signal tables as assistance. Measure between fuses and suitable ground terminals. If any problem is detected, troubleshoot the system in question.
Remove a fuse and read off the standby consumption according to the instructions above. If the power consumption has dropped to less than 25 mA, fault trace the system that the fuse corresponds to. if power consumption has not reduced, repeat the procedure with another fuse.
Note! Remove one fuse at a time and measure. Do not reinstall the fuses until the fault has been found, because it could awaken the car from "sleep mode " and restore the problem. If the vehicle was going to woken from "sleep mode" anyway, repeat the preparations for standby power consumption before continuing successive elimination.
If the fault has not occurred, continue with successive elimination on relays and the connectors for the vehicle's control modules.
Continue - DONE
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