15 Diagnosis of operation readiness of the rear oxygen sensor
(P0138, P0137, P0140, P0136)
The operation readiness diagnostic of the rear oxygen sensor runs continuously and can detect all faulty electrical connections of the of the rear oxygen sensor. Heater circuit faults are monitored separately.
20.2 Diagnosis during warm operation
During warm operation it is checked whether there is a permanent deviation between the current idle speed and the setpoint idle speed. Additionally it is necessary to take into account the condition of the ISC integrator.
The ISC integrator is a measurement for the regulated deviation to reach the setpoint idle speed and is limited to an upper and lower limit.
If the throttle valve opens to much it may happen that the idle speed rises above the fuel cut-off engine speed and the system starts oscillating. To cover this special case the number of detected fuel cut-offs during an idle phase is analyzed.
If
- the deviation (positive) between setpoint and current idle speed (underspeed) exceeds a calibrated threshold and
- the ISC integrator equals the upper maximum threshold limit and
- the engine load lies below a calibrated threshold
all for a calibrated period of time, a malfunction is detected and a LLRmin fault is set.
If the deviation (negative) between setpoint and current idle speed (overspeed) lies below a calibrated threshold and the ISC integrator equals the lower threshold limit and no fuel cut-off condition has been detected, all for a calibrated period of time, then the lower minimum integrator threshold limit is extended for further investigation.
If
- the deviation (negative) of the current engine idle speed lies below a calibrated threshold and
- the ISC integrator equals the new lower threshold limit and
- still no fuel cut-off condition has been detected
all for a calibrated period of time a malfunction is detected and a LLRmax fault is set.
If the number of detected fuel cut-offs during this idle phase exceeds a calibrated threshold for a calibrated period of time, a malfunction is detected and a LLRmax fault is set
38.1.1 General description of the Valvetronic electronic
The Valvetronic electronic is integrated in the ECU managing the functionality for adjusting the valve lift and the diagnosis of this control electronics. Regarding the valvetronic, permanently stored data after deactivation of the ECU includes: learning value for end position, diagnosis information for the manufacturer and configuration information.
Diagnosis of the Valvetronic system
Power stages: Diagnosis of short circuits and open load detection
Power supply: Diagnosis of the supply voltage via the Valvetronic relay
Valve lift adjustment: Diagnosis of the positioning control regarding regulation deviation, transient time and speed and further plausibility check of the rotation direction
Fail safe mode: Diagnosis of the fail safe mode position of the valve lift
38.2.1 Description and diagnosis of the Valvetronic system
The output stage of the valvetronic actuator is supplied by a relay, which is switched to the ECU. The voltage in the ECU is needed for the correction of the issued duty factor of the output stage, which is dependant to the battery voltage.
The supply voltage for the output stage is monitored permanently by the ECU and if the supply voltage gets out of the permitted range compared to the supply voltage via the main relay (delta 2,5V), then this malfunction will be detected and the DTC will be stored.
38.3.1 General description of this module
The valvetronic actuator is supplied by a power stage with integrated "Full-Bridge"-circuit in the ECU. With this "Full-Bridge"-circuit the sense of rotation of the actuator can perfectly be changed.
To avoid a damage of the power stage, a permanent monitoring of short circuit is proceeded.
Diagnosis of a malfunction within the Power Stage
By a series connection of shunts in the high side-and low side path a short circuit will be detected. In this case the power stage will be cut off and a detailed distinction of the different kinds of short circuits will be performed.
In the resistor network of the power stage circuit the voltage levels are measured and compared with the programmed thresholds (in accordance to the summary table).
Dependant to the deviation from the desired values there will be detected
> short to ground
> short to battery
> short with each other
> open load
and the corresponding DTC will be stored.
38.4.1 Description and diagnosis of this module
If a malfunction of one of the valvetronic components is detected, the management tries to drive the actuator to the end position (limp-home = full valve lift). In this case, the charge control will be managed by the throttle. If the actuator cannot reach its end position, the valvetronic tries to ensure, that the load on both banks reaches a common level. Any reduction of valvelift will lead to a reduction of the engine power.
A DTC is stored, if the actuator was not able to reach its end position.
There will be a distinction, whether this error was detected directly by a comparison with the actuator angle or indirectly by checking the comparison of the manifold pressure ratio, comparison of load or comparison of air mass flow.
44 Operation condition of WDA (watchdog output) signal
(P163E, P163D, P163C)
The function defines the ECU reaction to a WDA deactivation in the power stage.
The WDA monitoring consists of the following checks.
- monitoring of function controller
- monitoring of WDA (watchdog output) signal
- monitoring of internal supply voltage
If the monitoring module has detected a fault of the function controller by means of the inquiry- response communication, a malfunction is detected and a OCWDACom is set.
If the WDA signal is activated, a malfunction is detected and a OCWDAActv fault is set.
If the internal supply voltage exceeds a certain threshold, a malfunction is detected and a OCWDAOvrVltg fault is set.
46.1 General Description
Depending on the state of fault information, the standard output stage diagnosis will activate a fault check or a healing cycle. The diagram below has the following components or phases.
Scheme 101
- Fault check: Observing a buffer and detecting if a fault is present
- Fault de-bounce: A fault is detected. A counter then triggers a test impulse to confirm the fault.
- Verification: When the same error type is again detected, the fault is verified; otherwise it is rejected.
- Healing cycle: When a verified fault is stored in the fault code memory, a periodic healing cycle is initiated. After the healing cycle period, a test impulse is triggered. In case error flag is true on start there is no time delay to trigger the first test impulse.
- Fault check 2: If there is no fault signal detected after the healing cycle, the fault is healed. If the type of fault has changed or a verified fault is detected, the healing cycle is repeated.
48.1 General Description
The oil separation system is integrated in the cylinder head cover with 1 outlet. The blow by gas containing oil vapor is directed from the crankcase into the cylinder head cover through the oil separation system. Here the oil is separated from the blow by gas. The separated oil flows back to the oil sump. The blow by gas is drawn through a pipe into the intake manifold and further into the combustion chamber.
The pressure regulating valve, integrated in the cylinder head cover assures an under pressure in the crankcase / cylinder head.
49 Identification of communication protocol utilized by Engine N12 for communication with an SAE J1978 scan tool
The implementation and description of the diagnostic communication protocol KWP 2000 is based on the following standard
ISO 15765-4 Road Vehicles - Diagnostic Systems