16 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.
21.2 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 too 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.
49 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.
50.1 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.
- 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.
Scheme 154
52.1 General Description
The oil separation system is integrated in the cylinder head cover with 2 outlets. 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.
Under part load conditions (vacuum in the intake manifold): The blow by gas is drawn through a pipe into the intake manifold and further into the combustion chamber. The outlet under high load is closed via the nonreturn valve (flap).
Scheme 155
Under high load conditions (overpressure in the intake manifold): The blow by gas is drawn through a pipe into the air intake pipe located in front of the compressor of the turbo charger. The outlet for part load is closed via the other non return valve (flap)
The pressure regulating valve, integrated in the cylinder head cover assures an under pressure in the crankcase / cylinder head.
53 Identification of communication protocol utilized by Engine N14 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