Only for Z4 models with Siemens ECU MSV70: Engine Coolant Temperature 2 (ECT_2) Plausibility Check: General Description

WARNING: This page does not describe the selected car, but rather 8 other vehicles, including the 2008 BMW Z4, 2008 BMW X5, 2008 BMW X3, 2008 BMW 528xi, and 2008 BMW 528i. However, it is still accessible from the selected car via links, so may be relevant.

The diagnosis is based on monitoring the alternation of ECT_2 signal, positive and negative changes in three phases.

Just after start, if ECT and IAT (intake air temperature) is below an adjustable threshold, a too high ECT_2 can be detected by comparison of ECT at start and ECT_2 at start.

During warm - up phase (long term check, with no error detection) the diagnosis will only run if ECT at start and IAT lies within a tunable range after engine start. Minimum and maximum ECT_2 are continuously updated from engine start, after first being initialized to ECT_2 at power up. The difference between these two values, is also calculated. When this value exceeds a minimum threshold then the diagnosis is finished with a positive rationality check result.

After opening of thermostat, the long term check with error detection starts. The error detection is based on a change of ECT_2 after the opening temperature of the thermostat is reached and following the vehicle/engine is driven under certain conditions (vehicle speed, part load, engine speed, opening of thermostat) for a delay time. However, should one condition drop below the threshold or the engine exit part load state during this period, then the timer is reinitialized/incremented.

For RBM handling the Cold Start Denominator will be considered.