Diagnostic Overview
The ECM tests the catalyst system during steady state driving by cycling the fueling LEAN and then RICH for a calibrated number of cycles while monitoring the oxygen storage capacity (OSC). Prior to the Catalyst test the canister purge valve is completely closed or completely opened with low canister purge value. This is to eliminate the influence of canister vapors on the downstream sensor during the test.
The first lean to rich cycle of the test is only used to establish an average voltage value of the downstream sensor voltage. During subsequent cycles the OSC is based on the integrated (accumulated) value of the difference between the average value of the previous lean to rich cycle and the measured instantaneous voltage during the current lean to rich cycle.
General description of leak measurement
The evaporative system monitoring permits the detection of leaks in the evaporative system with a diameter of 0.02 inches and up.
By means of a Diagnostic Module Tank Leakage (DM-TL), an electrical actuated pump located at the atmospheric connection of the evaporative canister, a pressure test of the evaporative system is performed in the following order
Scheme 234
Scheme 235
Scheme 236
Scheme 237
- During the Reference Leak Measurement, the electrical actuated pump delivers through the reference restriction. The engine-management system measures the pump's electrical current consumption in this section.
- During the Leak Measurement, the electrically actuated pump delivers through the charcoal canister into the fuel-tank system. The pressure in the evaporative system may be up to 2.5 kPa depending on the fuel level in the tank. The engine-management system measures the pump's electrical current consumption. A comparison of the currents of the reference leak measurement and the leak measurement is an indication of the leakage in the tank. 0.02 inch diagnosis: The first step of the diagnosis is the reference measurement, the result of the pump reference current is stored (picture in chapter a). After the solenoid switches, the venting system is pressurized (picture in chapter b). In the rough leak measurement the rough leak threshold is reached, if the leak is smaller than 0.04 inch and then the small leak measurement phase follows. When the DMTL current reaches the reference current within the small leak time, the system is tight (leak smaller than 0.02 inch), otherwise a small leak between 0.02 - 0.04 inches is detected. 0.04 inch diagnosis: The first step of the diagnosis is also the reference measurement, the result of the pump reference is stored (picture in chapter a). After the solenoid switches, the venting system is pressurized (picture in chapter b). In the rough leak phase (time) the pump current must reach the rough leak threshold 1 (rough leak threshold 1 = idle current pump + K1 x (reference current - idle current). Factor K1 is between 0.16 and 0.28 depending on the characteristic current value of the pump (reference current - idle current), this value is various in every pump. If the rough leak threshold 1 is not reached in the rough leak time, the rough leak threshold 2 must be reached in an additional time (rough leak threshold 2 = idle current pump + K2 x (reference current - idle current). Factor K2 is between 0.60 and 0.80 depending on the characteristic current value of the pump (reference current - idle current). If the rough leak threshold 2 is also not reached, a leak > 0.04 inches is detected. In the diagram below is the typical current of a tight system, a 0.02 inch leak, and a leak > 0.04 inches.
- After the test the remaining pressure in the evaporative system is bled off through the charcoal canister by switching off the pump and solenoid.
Scheme 238
Scheme 239
General description of the PCV-System
There are 3 tubes connected to the engine: The first of them conducts the blow-by gases from the cylinder head cover to the separator, where the oil is separated from the air and lead back by a second tube to the crankcase sump. A third tube directs the cleaned blow-by gases via the intake system to the combustion. The pressure regulator makes sure that the high vacuum level between crankcase and ambient air will be reduced if needed.
General Description
The purpose of this diagnosis is to detect electrical faults as defined in OBDII requirements. The input signal is a CAN message of instrumentation cluster. If an error is present on CAN signal, an error symptom is set and an error counter is de-bounced.
This diagnosis is performed in order to detect a stuck or not plausible TAM signal which cannot be detected by electrical range diagnosis.
The first part, just after start looks at the change of ambient temperature and compares the start and stop temperature. If the check is positive the diagnosis is finished. In negative case diagnosis runs to next step during warm up phase.
The error detection is only performed if the monitoring conditions for time after start, engine state idle speed, time of engine stop, ECT and ambient temperature are fulfilled. The plausibility error is detected if the absolute value of the temperature-difference between the arithmetic mean of ECT (Engine Coolant Temperature) and TIA (Temperature Intake Air) and the ambient temperature TAM (in formula: ABS [(ECT+TIA) x 0,5 -TAM)]) exceeds the threshold for an anti-bounce time.
The error validation is only performed if ECT signal is valid and the vehicle was driven with a certain vehicle speed. If both conditions are true and an error was detected, then the error is set for this driving cycle and the diagnosis is switched off.
For RBM handling the Cold Start Denominator will be considered.
Diagnostic Overview / Monitoring Function
(P0171, 172,174, 175)
The ECM monitors the fuel system control continuously during all engine states except PUC (decal fuel cut-off). After the enable conditions are met a counter is started. At this point the ECM evaluates the total percentage of short and long term fuel control. If no condition is present the end diagnostic counter will decrement from a calibrated value to zero and a passing decision is made.
If a lean condition is present and total fuel control is above the calibrated threshold two timers are started. If the lean threshold counter exceeds the calibrated threshold before the reset timer has decremented from a calibrated threshold to zero a lean error is set.
If a rich condition is present and total fuel control is below the calibrated threshold two timers are started. If the rich threshold counter exceeds the calibrated threshold before the reset timer has decremented from a calibrated threshold to zero a rich error is set.
The time counter is increased while "lambda controller + lambda adaptation" exceed minimum or maximum threshold.
The error is detected as soon as the time counter reaches its maximum value.
Scheme 240
Monitoring Description
This function determines, if an open circuit in any of the four electric lines (Reference Voltage, Virtual Ground, Pumping Current and Trim Current) is present in the WRAF Sensor.
This function shall be triggered only if one of the following diagnosis is active (to set the readiness bit), which are 'Upstream Oxygen Sensor - Signal Monitoring During Fuel Cut-off and 'Upstream Oxygen Sensor - Heater Monitoring'. The function shall go to the state = "active" only if one of the above diagnosis detected a fault.
(Reference Voltage)
If a heater error exist and sensor voltage is too low, while the internal resistance measurement is turned off, an open circuit in the line 'Reference voltage' occurred.
(Virtual Ground) or (Pumping Current)
An open circuit in line Virtual Ground or in the line Pumping current can be detected if the sensor signal stocks near lambda 1. The sensor non-activity can be detected by the Oxygen Sensor Signal Monitoring During Fuel Cut-off (signal voltage below e.g. 2.1 V *) in fuel cut off).
(Trim Current) If the sensor shows an augmented gain, i.e. the sensor signal is higher than the nominal characteristic line, the plausibility test during the fuel cutoff phase shall detect this symptom (signal voltage above e.g. 5.6 V *) during fuel cut off) and an Open Circuit is assigned to the line Trim Current.
)* For exact values please have a look at the summary table!
Sec (e) (7.2)
This function will detect an error during the initialization and/or operation of a WRAF sensor controller through SPI communication. Information communicated from the Basic Software (BSW) is used for initialization and communication between application software (ASW) and the controller. This is used to determine if the function is working properly.
This function will detect if the Oxygen Sensor wire harness has been cross connected, i.e., Bank 1 with Bank 2. This is performed by the use of the output of the fuel correction (lambda controller) of each bank. If this control is on opposite limit at bank 1 and bank 2, the sensors are swapped and the corresponding fault code is stored.
Corresponding fault code
P0040
Sec (e) (7.2.3)
The purpose of this function is to detect oxygen sensor heater failures that would lead to an increase in emissions beyond the thresholds stated in the appropriate regulations.
The diagnosis shall be carried out by determining whether the measured oxygen sensor ceramic temperature falls below set limits over a number of measurement cycles. The evaluations of the diagnosis cycle are determined after the completion of a limited number of monitoring cycles.
Deviations in the oxygen sensor ceramic temperature or the oxygen sensor not being operatively ready in a timely manner (because of a too low temperature) can lead to an increase in emissions above the applicable standards or prevent the sensor signal from being used as a diagnostic system monitoring device. Deviations may occur due to, for example, ageing of the heater element, defective wiring, increased heater circuit connector contact resistance, defective heater driver etc.
The purpose of this diagnosis is to detect electrical faults of the sensor signal. The input signal is analog from a NTC and has to be in a calibrated range. Short cut to ground can be detected immediately, short cut to voltage battery or open load after a delay time. If an error symptom is detected, the error counter is de-bounced.
The purpose of this diagnosis is to detect an implausible gradient on the coolant temperature signal. The diagnostic function checks whether the difference between one measured coolant temperature value and the succeeding value is too big.
The purpose of this diagnosis is to detect a stuck coolant temperature signal. The diagnostic function checks if after a variation of the calculated coolant temperature also a variation of the measured coolant temperature is detected.
For RBM handling the Cold Start Denominator will be considered.
The engine off time is calculated by a relative time counter of an instrumentation CAN message. After evaluation of this message the engine off time is compared with the difference of ECT at engine stop and ECT. This is to check if the engine off time is within a certain temperature range.
The engine off time is calculated by a relative time counter of an instrumentation CAN message. After evaluation of this message the engine off time is compared with the difference of ECT at engine stop and ECT. This is to check if the engine off time is within a certain temperature range.
Description of the Engine Coolant Thermostat Monitoring
The coolant thermostat monitoring is done to detect a slow warm-up due to heat losses through thermostat and radiator. It is based on the comparison of the measured ECT sensor signal and the calculated ECT model (TCO_SUB).
The ECT model calculation is depending on the speed of the water pump, engine load and ambient temperature.
A malfunctioning coolant thermostat is detected, if the calculated ECT model has exceeded the threshold 1 (P0128) and the measured ECT sensor signal remains below threshold 2 (P0128).
Before a malfunctioning coolant thermostat is entered into failure memory, the conditions concerning low load, coasting duration and IAT during the monitoring are checked. If the monitoring conditions are met, the coolant thermostat is entered into failure memory. Otherwise the coolant thermostat monitoring is inhibited for this driving cycle.
The purpose of this diagnosis is to detect electrical faults as defined in OBDI requirements. The input signal is analog from a NTC and has to be in a calibrated range. Short cut to ground can be detected immediately, short cut to voltage battery or open load after a delay time. If an error symptom is detected, the error counter is de-bounced.
This diagnosis checks IAT integrity for a plausible range and / or signal stuck. For the range detection, IAT has to be within coolant temperature and ambient temperature window. If IAT is outside of the range plus an offset, the error symptom is set and the error counter is de-bounced.
If the vehicle was driven with a certain vehicle speed for a calibrated time (cool down of hot IAT) and afterwards the vehicle was in idle for a calibrated time, and the IAT signal has not moved, then a stuck IAT signal is detected and the error is de-bounced.
For RBM handling the Cold Start Denominator will be considered.
Description
In this diagnosis module the difference between the actual and target position of the Vanos units ("control deviation") is checked. If the calculated difference between these two positions exceeds the established threshold, a counter is started. The counter is incremented twice per crank revolution (but not exceeding 10 msec-rates).
If the counter exceeds a limit (also adjustable), a Rationality Fault (DTC) is stored.
The control deviation diagnosis has got an interface to the Rate-Based Monitoring module.
- In-use monitor performance Ratio: The incrementing of the numerator, denominator, and the ratio calculation for the Variable Camshaft Timing monitor is executed by the Rate-Based Monitoring module. Like all monitors for which a standardized track and report in-use performance is required, the Variable Camshaft Timing monitor reports to the RBM-module via status flags.
- Conditions for incrementing the Numerator: The numerator is incremented if and only if the monitor is not inhibited due to stored faults and the diagnostic has been performed and a fault would have been detected.
- Conditions for incrementing the Denominator: The denominator is incremented if the monitor is not inhibited due to stored faults, the general driving conditions have been fulfilled and all additional physical conditions for incrementing have been fulfilled.
The purpose of the diagnosis is to detect when the camshaft reference position is outside the designed range relative to the engine position from crankshaft and to detect a signal which is not valid.
The diagnostic strategy for inlet and exhaust camshaft is identical.
The purpose of the diagnosis is to determine whether the inlet (first) camshaft is used for engine synchronization or the exhaust camshaft.
The purpose of this diagnostic is to check the integrity of the crankshaft sensor signal and/or electrical malfunctions. (Open line, SCG, SCVB)
Descriptions
The electronic control of the Variable Valve Lift positions is dependant on, Voltage Limits, Start & Stop position, Adaptations, current and temperature. The following errors will be detected in this system.
Electrical diagnosis is performed internally to the controller in order to detect the following errors: Short circuit to battery, to ground or short circuit to each other
SCVB - P1047
SCG-P1048
S together - P1049
System current is monitored through the ECU and the variable valve train relay. This diagnosis checks for over-temperature and overload conditions and performs short term and long term high current monitoring (looks for current spikes over a threshold, and time vs. current table based)
Relay over temp - P1076
Relay overload - P1075
Relay overload - P103A
VVL Bus Conductor Temp - P1078
VVL Power Stage Warning - P107A
VV Train Bus Conductor Temp - P107B
VVL Power Stage Warning - P107C
Powerstage self diagnosis is performed to realize if power stage diagnosis has detected under voltage or overcurrent of high or lowsider. The diagnosis is a self check realized therefore in the specific hardware (powerstage).
undervoltage of driver - P105B
overcurrent detection on high side / low side of H-bridge - P105A
Power Supply Control Motor is monitored through the main relay and checks over and under voltage conditions. There is also a Power Supply sensor diagnosis which checks short circuit to battery and to ground. If this occurs, the following DTC's will be stored
Power Supply over voltage - P1055
Power Supply Under Voltage - P1056
Power Supply Sensor SCVB - P1019
Power Supply Sensor SCG - P1020
VVL Relay Diagnosis is performed internally to the ECU and does a comparison of the main relay voltage to the variable valve lift capacitors. If the difference is greater than a threshold then an appropriate DTC will be stored.
Relay Diagnosis - P1057 (Battery Main Relay Voltage - Capacitor Voltage)
Sensor Diagnosis is performed internally to the ECU and checks the sensor supply voltage to tunable boundaries. A sensor signal versus an internal sensor self check will determine the integrity of the sensor. If an error is detected, the appropriate DTC will be stored.
Sensor Signal fault - P1017 (ECU check)
Control Position Diagnosis and the Value Comparison Diagnosis are used to monitor the start and stop positions and the current PWM signal movement of the variable valve train system. If the difference between the target and actual angle is determined to be greater than a threshold percentage an error is detected, if a difference in the start and stop positions are greater than a threshold an error is detected. If any of these errors is detected, the appropriate DTC will be stored
Control Position fault - P1030 (PWM out of range)
Value Comparison fault - P1064 (Difference)
Self Learning / Adaptation Diagnosis is performed internally to the ECU. There are three adaptation diagnoses performed in this function, the top and bottom limit individually out of range and both limits out of range. Furthermore the ECU self check diagnosis is performed, which is basically a check sum error. If any of these errors is detected, the appropriate DTC will be stored
Top Limit Fault - P101A (top limit not reached)
Bottom Limit Fault - P1023 (bottom limit not reached)
Both Adaptations Fails - P1024 (both limits not reached)
ECU Check Sum Error - P1041
Scheme 241
Monitoring Descriptions
ETC Driver diagnosis (H-bridge): The ETC - H-Bridge IC continually checks the MTC if there is a short circuit to battery voltage or ground. In addition the IC is able to detect overtemperature. This is performed internally to the ECU.
The purpose of this diagnosis is to detect electrical faults of the idle speed controller circuit. The controller is PWM modulated, inverse output signals are used for continuous activation of the opening and closing of a double-wound coil actuator.
The error detection is activated at Key "ON". The following errors are detected
- Short to ground
- Short to battery
- Open circuit
If any of the above errors are detected during opening or closing of the controller, the appropriate DTC will be stored.
Depending on engine speed, valve-lift, inlet camshaft position, outlet camshaft position and manifold pressure an air mass flow into the cylinder is calculated. There is also a correction of the calculated air mass flow depending on intake air temperature, coolant temperature and ambient pressure. The ratio between the measured air mass flow and the calculated air mass flow must be between calibrated MIN/MAX-values. If the MIN/MAX thresholds are exceeded, a time counter is incremented. After this counter reaches the threshold within one diagnosis cycle, an air mass flow meter malfunction is detected.
For a variable valve lift engine, the main function of the throttle body is to control the pressure in the intake manifold. Therefore the manifold differential pressure plausibility check is testing the plausibility of measured intake manifold pressure in comparison to the measured throttle position. So no throttle position acquisition error must be present.
The setpoint of the differential intake manifold pressure is up to 60-70% of maximum torque request constant 5 kPa beneath ambient pressure. At higher load the differential pressure setpoint becomes Zero.
In case the setpoint of the differential pressure in the intake manifold is > 3 Kpa beneath the ambient pressure, a differential pressure controller is active. The output of the controller is monitored. The output of the manifold pressure controller has to be between calibrated MIN/MAX-thresholds. If the MIN/MAX thresholds are exceeded a time counter is incremented. After this counter reaches the threshold within one diagnosis cycle, a manifold differential pressure sensor malfunction is detected.