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Part 7

14 COMPREHENSIVE COMPONENTS MONITORING Contd.

14.17 Crankshaft Position Sensor

14.17.1 General Description
The crankshaft position sensor detects the revolutions of the crankshaft by means of periodic gaps in the ring gear of the flywheel. These periodic gaps cause cyclic changes in the magnetic field while the crankshaft rotates, which are detected by an inductive pickup.

14.17.1 Crankshaft Position Sensor, Signal irrational, P0321

Monitoring Strategy
The signal of the crankshaft position sensor is continuously monitored and evaluated.

Typical Enable Conditions
- None

Malfunction Criteria
If the number of detected signal flanks during one crankshaft revolution differs from the number of teeth on the flywheel, or a fault is found by the "signal monitoring" function, an irrational signal is detected and the corresponding fault is stored in the fault memory.

The "signal monitoring" function checks the rationality of the sensor signal according to the following criteria:






14.17.2 Crankshaft Position Sensor, no Signal, P0322

Monitoring Strategy
The signal of the crankshaft position sensor is continuously monitored and evaluated.

Typical Enable Conditions
- None

Malfunction Criteria
If the camshaft position sensor signal has been verified by the camshaft position sensor monitor AND no signal from the crankshaft position sensor has been received within a defined number of camshaft revolutions, a signal fault is detected and the corresponding fault is stored in the fault memory.






14.18 Camshaft Position Sensor

14.18.1 General Description
The camshaft position sensor detects the camshaft revolutions by means of a rotating magnetized trigger wheel fixed to the camshaft. Regular gaps integrated in the trigger wheel cause cyclic changes in the magnetic field while the camshaft is rotating, which are detected by a Hall sensor.

14.18.2 Camshaft Position Sensor, Signal permanently high, P0343, P0348, P0368, P0393

Signal permanently high:
Inlet side, bank 1: P0343; inlet side, bank 2: P0348
Outlet side, bank 1: P0368; outlet side, bank 2: P0393

Signal permanently low:
Inlet side, bank 1: P0342; inlet side, bank 2: P0347
Outlet side, bank 1: P0367; outlet side, bank 2: P0392

Monitoring Strategy
The signal of the camshaft position sensor is continuously monitored and evaluated.

Typical Enable Conditions
- None

Malfunction Criteria
Signal permanently high:
If the level of the camshaft position sensor signal is permanently at the maximum value within a defined number of crankshaft revolutions (with no camshaft signal flank occurring) AND if the crankshaft position sensor signal has been verified by the crankshaft position sensor monitor, a permanently high signal is detected and the corresponding fault is stored in the fault memory.

Signal permanently low
If the level of the camshaft position sensor signal is permanently at the minimum value within a defined number of crankshaft revolutions (with no camshaft signal flank occurring) AND if the crankshaft position sensor signal has been verified by the crankshaft position sensor monitor, a permanently low signal is detected and the corresponding fault is stored in the fault memory

14.18.3 Camshaft Position Sensor, Signal irrational, P0341, P0346, P0366, P0391
Inlet side, bank 1: P0341; inlet side, bank 2: P0346
Outlet side, bank 1: P0366; outlet side, bank 2: P0391

Monitoring Strategy
The signal of the camshaft position sensor is continuously monitored and evaluated

Typical Enable Conditions
- None

Malfunction Criteria
If the number of detected positive signal flanks during one camshaft revolution differs from the number of gaps in the rotating trigger wheel, OR if the gap between two signal flanks is outside of the calibrated tolerance, OR if the signal level is outside of the rational range, a faulty signal is detected and a fault counter is incremented. If the fault counter reaches a defined threshold value, an irrational signal is detected and the corresponding fault is stored in the fault memory.


14.18.4 Angular Offset between Camshaft and Crankshaft, P0016, P0018, P0017, P0019
Inlet side, bank 1: P0016; inlet side, bank 2: P0018
Outlet side, bank 1: P0017; outlet side, bank 2: P0019

Monitoring Strategy
The signal of the camshaft position sensor is compared to the signal of the crankshaft position sensor.

Typical Enable Conditions
- None

Malfunction Criteria
The signal flanks that are continuously detected by the camshaft position sensor and the crankshaft position sensor are sent to the ECM and stored in a buffer memory. Every 100 ms, the monitoring function evaluates the signal flanks detected since the last evaluation. The "available" camshaft signal flanks during these time segments must correspond to at least one complete camshaft revolution. If not enough signal flanks occur, the evaluation is interrupted until the next time segment is reached.
The angular offset between the camshaft and the crankshaft is calculated from the gap between the equidistant flanks of the camshaft signal and the camshaft setpoint positions defined by the crankshaft signal flanks. A mathematical average is calculated from this angular offset and is filtered with a PT1 element (first-order low-pass filter). If this filtered value is greater than a defined upper threshold value or less than a defined lower threshold value, an angular offset between the camshaft and the crankshaft is detected that is too large, and the corresponding fault is stored in the fault memory.










14.19 Atmospheric Pressure Sensor / Altitude Sensor

14.19.1 General description
The atmospheric pressure sensor (or altitude sensor) measures the atmospheric pressure of the area surrounding the vehicle (ambient pressure).

The atmospheric pressure sensor monitor checks for circuit continuity, out of range signals and a rationality check.

14.19.2 Monitoring function description

Circuit Continuity
If the atmospheric pressure exceeds an upper limit for too long, a short circuit to battery is detected and a Atmospheric Pressure Circuit High fault is set.

If the atmospheric pressure stays below a lower limit for too long, a short circuit to ground is detected and a Atmospheric Pressure Circuit Low fault is set.

Range Check
If the atmospheric pressure exceeds an upper limit for too long, out of range high is detected, and a Atmospheric Pressure Circuit fault is set.

If the atmospheric pressure stays below a lower limit for too long, out of range low is detected, and a Atmospheric Pressure Circuit fault is set.

Key On, Engine Off (KOEO) Check
The KOEO check compares the atmospheric pressure at KOEO with the value stored at the last engine shut down. If this is not the same, and the atmospheric pressure is not similar to the upstream throttle pressure at KOEO, an Atmospheric Pressure Circuit Range/Performance fault is set.

14.19.3 Flow charts atmospheric sensor monitoring






Flow chart atmospheric sensor monitoring - sub-routine "rationality check"






14.19.4 Control Module Fault, Altitude Sensor Rationality check high / low, P0606

Applicable only for test groups






Monitoring Strategy
At "ignition on" and "engine off", the current measured value of the altitude sensor is compared to the last stored measured value in the previous driving cycle. If a fault indication is made upon this comparison, the current measured value of the altitude sensor is compared to a modeled reference ambient pressure.

Additionally, in a defined time pattern the gradients of the altitude sensor signal are continuously calculated and evaluated. If a fault indication is made upon this comparison, the current measured value of the altitude sensor is compared to a modeled reference ambient pressure, too.

Additionally, the measured values of all used air pressure sensors are compared to each other at engine-on after a sufficiently long engine-off time.

Typical Enable Conditions
- Engine-off time greater than defined threshold value (only for the comparison of the air pressure sensors)
- Engine speed less than defined threshold value (only for the comparison with the measured value of the previous driving cycle and for the comparison of the air pressure sensors)
- Time since engine-on less than defined threshold value (only for the comparison with the measured value of the previous driving cycle)
- Throttle position less than defined threshold value (only for the comparison with the measured value of the previous driving cycle)

Malfunction Criteria
At "ignition on", but before the engine is started, the current measured value of the altitude sensor is compared to the last measured value taken and stored in the previous driving cycle. If, upon this comparison, the current measured value of the altitude sensor is greater than / less than the measured value stored in the previous driving cycle by at least a defined positive / negative threshold value, an irrationally high / low signal of the altitude sensor is detected and a fault indication is set. The change of the measured ambient pressure during the engine-off time between the previous and the current driving cycle is considered irrational if it has such a large value that it could not have been caused by a weather-related air-pressure change.

Additionally, in a defined time pattern the gradients of the sensor signal are continuously calculated. If the signal of the altitude sensor increases / decreases by more than a defined positive / negative threshold value within a defined time period, an irrationally large change of the sensor signal is detected, and a fault indication is set. This defined positive / negative threshold value is defined in such a way that it is not exceeded if an ambient pressure change occurs which corresponds to the fastest possible downhill / uphill driving under realistic driving conditions.

If a fault indication is set, a reference ambient pressure is calculated for the remaining part of the monitoring from the measured values of the MAP sensor. An upper threshold value and a lower threshold value are calculated from this reference ambient pressure which limits the rational range of the altitude sensor. If the measured value of the altitude sensor is outside this modeled rational pressure range, a fault is registered.

Moreover, at engine-on a mean value is calculated from the current measured values of all air pressure sensors used in the vehicle. This mean value is subtracted from the current measured ambient pressure value. If the resulting difference is greater than / less than a defined positive / negative threshold value, an irrationally high / low ambient pressure is detected and a fault is registered in the fault memory.






14.19.5 Short to Battery/Ground or Open Circuit

Monitoring Strategy
The signal voltage of the altitude sensor is continuously monitored.

Typical Enable Conditions
- None

Malfunction Criteria

Short to ground, P0606:
If the signal voltage of the altitude sensor is less than a defined threshold value for a defined time period, a short to ground is detected and a fault is stored in the fault memory.

Short to battery or open circuit, P0606:
If the signal voltage of the altitude sensor is greater than a defined threshold value for a defined time period, a short to battery or an open circuit is detected and a fault is stored in the fault memory.
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