9.1.1 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.
9.3.1.1 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
- 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 237
Scheme 238
Scheme 239
9.5.1 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.
9.6.1.1 General Description
The purpose of this diagnosis is to detect electrical faults as defined in OBDII requirements. The input signal is analog from CAN. If an error is present on CAN signal, an error symptom is set and an error counter is de-bounced.
9.6.2.1 General Description
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 on 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 temperature-difference to oil temperature exceeds the threshold for an anti-bounce time.
The error validation is only performed if all electrical diagnoses for ECT and radiator outlet temperature are finished 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.
9.7.1 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
9.8.1.2.2 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 Plausibility Check, Plausibility during fuel cutoff, and Sensor Heater OBD2. The function shall go to the state = "active" only if one of the above diagnosis de-bounced a fault. In this state, if a heater OBD2 error exists, the WRAF sensor controller oscillator used to measure the sensor internal resistance shall be disabled in order to allow stable plausibility error detection. After the deactivation of this function the oscillator shall be re-enabled.
During the diagnosis state "active" a timer shall run waiting for OBD2 heater monitor to complete. If a heater OBD2 error could be detected, the timer should be stopped and a symptom set, otherwise it should run until it reaches the max value.
(Reference Voltage) If a heater error and a plausibility error (symptom "sensor too rich/lean") or an open circuit error in the line Reference Voltage exists.
(Virtual Ground) An open circuit in line Virtual Ground can be detected if a heater OBD2 fault is present and the sensor is not active anymore, i.e. the signal sticks near lambda 1. The sensor non-activity can be detected by anyone of the following diagnosis: plausibility (symptom is "sensor not active"), or plausibility during PUC (symptom signal too low).
(Pumping Current) If the delayed diagnosis timer expired, it is assumed that no heater OBD2 fault exists. A plausibility (symptom is "sensor not active"), or plausibility during PUC (symptom signal too low) indicates that an Open circuit in the line Pumping Current occurred.
(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 and an Open Circuit is assigned to the line Trim Current.
9.8.1.3.1 Diagnostic Overview
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.
9.8.1.5.1 Monitoring Description: (P0040)
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 O2 signal of each bank and is performed internal to the ECU.
9.8.1.8.1 Diagnostic Overview
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 operative readiness of the sensor exceeds a time threshold, or whether the measured oxygen sensor ceramic temperature exceeds or 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 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.
9.8.2.2.1 Monitoring description: (P0041)
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 O2 signal of each bank. This is performed internal to the ECU.
Scheme 241
9.10.1.1 General Description
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.
9.10.2.1 General Description
There are two different strategies / functions that can be used to determine if sufficient coolant temperature has been reached to enable Closed Loop Fueling.
- ECT Model Based vs. Actual ECT: This function detects if ECT has reached sufficient temperature to allow closed loop fuel using an ECT model vs. measured ECT. If this error is detected then the ECT model temp is used and the diagnostic trouble code (P0125) will be stored. The error will latch for this drive cycle (until power latch occurs). (Scheme 242)below
9.10.3.1 General Description
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.
9.11.1 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 engine load/speed and the intake air temperature.
A malfunctioning coolant thermostat is detected, if the calculated ECT model has exceeded the threshold 1 (ST; >103°C) and the measured ECT sensor signal remains below threshold 2 (ST; <92°C).
We avoid a too early opening of the thermostat and thus an erroneously error detection.
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.
Scheme 242
A comparison between the measured coolant temperature and the "warmed-up temperature" is done after a specific time interval. The interval itself is based on the coolant temperature model (Function of intake air mass).
As soon as the model temperature exceeds the thermostat opening temperature and all other monitoring conditions are fulfilled at the same time, a valid diagnosis occurs.
At that time, if the measured coolant temperature is higher than warmed-up temperature, the thermostat is concluded as normal thermostat.
On the contrary, if the measured coolant temperature is lower than warmed-up temperature, the thermostat is concluded as opened stuck thermostat.
9.12.1.1 General Description
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 debounced.
9.12.2.1 General Description
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.
9.13.1.4.1 Description
The purpose of this diagnosis is to detect electrical malfunctions of the variable cam timing solenoid. This is done internal to the ECU when the ignition is powered "ON".
9.13.1.5.1 Description
The purpose of this diagnostic is to verify the alignment of the camshaft and crankshaft has not slipped or been misaligned. This is done in addition to monitoring the electrical diagnosis of the sensors. The diagnosis begins when the engine starts and is continuous through the complete driving cycle and engine speed is "0".
One Tooth Off Target
Verification is performed by comparing the current values to the saved value from the adaptation phase, if the difference is greater than or less than a threshold, the appropriate DTC will be stored. This adaptation phase is performed during base timing occurrences and the diagnosis is performed after each adaptation phase. This will occur at a minimum, each driving cycle. See figures 1, 2, & 3 below
9.13.2.1 Description
The purpose of this diagnostic is to check the integrity of the crankshaft sensor signal and/or electrical malfunctions. (Open line, SCG, SCVB)
9.14.1 DESCRIPTIONS
The electronic control of the Variable Valve Lift positions is dependent 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 (temperature > tbd°C)
Relay overload - P1075 (overload current > tbd amp)
Relay overload - P103A (short term high current, table based, current vs. temp)
VVL Bus Conductor Temp - P1078 (> tbd°C)
VVL Power Stage Warning - P107A (High Current)
VV Train Bus Conductor Temp - P107B (> tbd°C)
VVL Power Stage Warning - P107C (High Temp > tbd°C)
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 (> tbd Volts)
Power Supply Under Voltage - P1056 (< tbd Volts)
Power Supply Sensor SCVB - P1019 (> tbd Volts)
Power Supply Sensor SCG - P1020 (< tbd Volts)
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 > tbd)
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 243
9.15.1.1 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 over temperature. This is performed internally to the ECU.
9.16.1.1 General Description
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.
9.17.1.1 GENERAL DESCRIPTION
The purpose of this diagnosis is to detect electrical faults as defined in OBDII requirements. The input signal is analog from a NTC and has to be in a calibrated range. Short to ground can be detected immediately, short to battery or open line after a delay time.
If an error symptom is detected, the error counter is de-bounced.
9.18.1 DESCRIPTION
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.
9.19.1 DESCRIPTION
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 set point 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 set point becomes Zero.
In case the set point 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.
