Engine Controls - False Low Oil Level Lamp Illumination
GROUP 11Engine
11 09 00
Woodcliff Lake, NJ
Service Engineering
December 2000
SUBJECT
Thermal Oil Level Sensor Diagnostics
MODEL
All
SITUATION
The low oil warning is shown on the instrument cluster either as a text display "Check oil" (vehicles with IKE) or as an amber warning indicator. The warning (set by the check control system) may be a Priority 1 (comes on while driving) or Priority 2 (comes on when the ignition is turned off). The operating principle is that a heating element in the sensor heats the sensor above the temperature of the oil, then the time taken for the sensor to cool back down indicates the level of the oil. The longer the "cool down" time is, the lower the oil is in the engine.
When carrying out troubleshooting, these "cool down" (low time) signals can be monitored using DIS or MODiC. In cases where a customer complains of sporadic low oil warnings, troubleshooting is more effective if the thresholds which trigger the warnings are known by the diagnostic technician.
CORRECTION
For a functional description (FB) of the thermal oil level sensor operation, refer to DIS or MODiC. As different paths exist to locate the Functional Description (depending on vehicle I engine combination), it is suggested that for quick reference, manually select (vehicle not connected to tester) as follows: "E46, Function Description / Complete vehicle / Body / Displays and information / Warning and indicator lamps / Oil level Warning / Documents"
When carrying out problem diagnosis:
1. First check the vehicle oil level with the dipstick and top up if necessary. (This may be the reason the warning is set).
2. Refer to Service Information bulletins 11 51 00 (X5) or 11 08 00 (525i). Early production vehicles (both X5 with M62, and E39 (525i)) require a coding change to correct a condition where the low oil warning is set.
3. If further diagnosis is required, using DIS, or MoDiC, monitor the thermal oil level sensor "cool down" (low time) signals as detailed below.
The levels to set the Priority 1 and Priority 2 warnings are different for each vehicle/engine combination, and are tabled below.
-- The Priority 1 warning is set if the measured "cool down" (low time) is higher than that listed in the Priority 1 column.
-- The Priority 2 warning is set if the measured "cool down" (low time) is higher than the time listed in the Priority 2 column, but lower than that listed in the Priority 1 column
-- Start engine
-- Select "Diagnosis"
-- Select "Function selection / Complete vehicle / Body / Displays and info / Warning and indicator lamps / Oil level warning"
-- Press "Test plan" and follow the Test plan instructions
-- Monitor the cool down times as the engine warms up and at different engine speeds.
E38, E39, E52, E53
-- Start engine
- Select "Diagnosis"
-- Select "Function selection / Complete vehicle / Body / Lights"
-- Press "Test plan"
-- Select "LCM / Check control / Expert mode / Test modules / Thermal oil level sensor"
-- Monitor the cool down times as the engine warms up and at different engine speeds.
Z3
-- Start engine
-- Select "Diagnosis"
-- Select "Function selection / Complete vehicle / Drive / Oil level monitoring" Press "Test schedule", and follow the test instructions.
-- Monitor the cool down times as the engine warms up and at different engine speeds.
Notes:
1. Cool down times are averaged over a minimum of 350 individual measurements in order to take account of slosh which occurs during normal driving. If this average is outside the warning threshold, the low oil warning is set. This means that just one or two momentarily high readings will not trigger the warning.
2. Diagnosis tip: Low voltage across the thermal oil level sensor can cause the low oil warning to set, even though the "cool down" values remain within acceptable limits. In this case, and before considering part replacement, check both the sensor supply (battery voltage) and sensor ground for any voltage drop. To make these voltage measurements, make up (3) "Y" adapters using the following components (from Electrical Repair Kit # 4):
Make each "Y" adapter as follows:
Cut two pieces of wire (1) approximately 150 mm long, and strip the insulation from each end.
Twist the wires together at the conductor end.
Using wire cutters, cut a male pin from the comb connector (P/N 61 13 1 387 150). Solder the wire pair at the twisted end to the male pin (2).
Crimp a contact sleeve P/N 61 13 1 387 142 (female connector) (3) to the open end of one of the wires.
Insulate each joint with shrink tubing (4).
Repeat the process to complete the remaining two "Y" adapters
Disconnect the electrical connector at the thermal oil level sensor, and insert the three "Y" adapters, male pins into the female terminals (1), and female connectors into male terminals (2).
With the engine running, use a multimeter and check the voltage at the sensor (pin 1) (battery voltage, >12V), and the sensor (pin 2) (ground, OV).
Troubleshoot the wiring harness if a measured voltage is not correct.
PARTS INFORMATION
WARRANTY INFORMATION
For information only