Emissions - 'Exhaust Fluid Low' Warning Displayed
SI B16 03 10Fuel Supply Systems
April 2011
Technical Service
This Service Information bulletin supersedes SI B16 03 10 dated April 2011.
[NEW] designates changes to this revision
SUBJECT
"Exhaust Fluid Low" Warning Displayed Before Oil Service
MODEL
E70 and E90 with M57Y engine
SITUATION
The customer receives a warning message stating that the diesel exhaust fluid level is low, and the engine will not restart in 999 miles or less. The warning comes a few thousand miles prior to the recommended oil service being due.
CAUSE 1
Diesel exhaust fluid (DEF) was not properly refilled during the service. The Selective Catalyst Reduction (SCR) system has used up the remaining DEF.
CAUSE 2
There was no DEF transfer from the passive tank to the active tank. Fault Code 46EB "Reducer inter-tank pump unit" may also be stored in the DDE.
[NEW] PROCEDURE 1
Current BMW models have a capacity of approximately 6 gallons of DEF. Add the necessary amount of fresh DEF to the existing amount to completely fill both tanks of the system at every oil service. Problems caused by an improperly maintained SCR system are not a matter for warranty.
PROCEDURE 2
Check the fill levels of the passive and active tanks, using ISTA/D 2.21 Test plan "B1365_D7SCRRES-Nachtankerkennung Activate Refuel Detection". If the active tank is empty and the passive tank is full, there has been no transfer of DEF. There could be several reasons for a no-transfer condition:
1. The DEF transfer pump is not working properly.
[NEW] Check the operation of the transfer pump using ISTA/D test plan "B1365_D7SCRTPMP SCR: transfer pump". The test will run the transfer pump until the active tank is full. If the active tank has been filled before this check, it will be necessary to drain a minimum of 0,5 liter (1 pint) of DEF from the active tank. Does the pump run? Does it transfer the DEF? Are there signs of DEF leaking out of the electrical connector on the pump (internal seal failure of the pump)? On new cars with low mileage, there is the possibility that the transfer pump is dry and will not create enough suction to transfer the DEF (fault code 46EB will also be stored). Run the above test plan to activate the transfer pump, but with the feed line to the active tank disconnected from the transfer pump. The pump will be able to create enough suction at this point to start transferring DEF. Once the pump does transfer DEF, it will no longer need this priming action to pump DEF. Fault code 46EB can only be deleted after the activation of the refuel detection. This should be done with service function "B1365_D7SCRRES Activate Refuel Detection". Both tanks must be refilled before running the refuel detection. Now the fault memory can be deleted.
2. There is a break or disconnection in one of the DEF lines to or from the transfer pump.
Check the DEF lines and connections at the passive tank; from the passive tank to the transfer pump; and from the transfer pump to the active tank. Check for loose connections, cut or pinched lines.
3. There is a restriction or blockage at the check valve on the transfer line at the active tank.
The amount of DEF transferred is based upon a given flow rate of the pump, not by volume. If there is a restriction or blockage in the line, the correct amount of DEF will not be transferred.
4. The DEF in the passive tank is frozen
If the outside temperature is 25°F or lower, the DEF will freeze. If this lower temperature lasts for an extended period of time, the DEF in the passive tank will never fully thaw, and transfer of fluid will cease. Only the DEF in the active tank will be utilized for the SCR injection. A full active tank will have enough DEF for approximately 3,000 miles of driving. If freezing is found to be a root cause, inform the customer that the or she may be required to top up the active tank periodically until the DEF in the passive tank has thawed.
[NEW] WARRANTY INFORMATION
This service information bulletin is intended to provide technical diagnostic and/or repair information.
If a warranty claim results from the above repairs, it should be submitted following the regular warranty claim procedures.