Diagnostic Trouble Codes with Test Charts (6-CYLINDER): Other BMW Z3 E36 рестайлинг

CHECK ENGINE LIGHT

CHECK ENGINE or Malfunction Indicator Light (MIL) is illuminated when any of the following occur

Scheme 147

1. Completion of the next consecutive driving cycle where the previously faulted system is monitored again and the emissions relevant fault is again present. (Scheme 147)
2. Immediately if a catalyst damaging fault occurs.
3. A malfunction of a component that can affect the emission performance of the vehicle occurs and causes emissions to exceed 1.5 times the standard.
4. Manufacturer-defined specifications are exceeded.
5. An implausible input signal is generated.
6. Catalyst deterioration causes HC-emissions to exceed a limit equivalent to 1.5 times the standard.
7. Misfire faults occur.
8. A leak is detected in the evaporative system.
9. The oxygen sensors observe no purge flow from the purge valve/evaporative system.
10. Engine control module fails to enter closed-loop operation within a specified time interval.
11. Engine control or automatic transmission control enters a limp home operating mode.
12. Key is in the ignition on position before cranking (Bulb Check Function).

DIS Plus

BMW DIS Plus diagnostic system features a comprehensive multimeter system (including an oscilloscope) that is used to perform various tests and measurement during the diagnosis and troubleshooting procedures. DIS also includes the Technical Information System (TIS). TIS is the same system that operates through dealer main computer system.

Group Tester One (GT-1)

GT-1 replaces the MoDiC series of portable diagnostic tools. It has the same processor as the DISplus. Other features include a DVD ROM drive, TFT color display, integrated PCMCIA card reader, integrated chip card reader, touch screen (same as DISplus), workshop grade case, ASM-technology motherboard, temperature operating range from 35°F to 105°F, 2.5 hours of operation with a fully charged battery, and can be powered by vehicle battery.

A diagnostic cable is used to connect diagnostic head to a vehicle with the 20 pin underhood connector. Cable consists of 20 pin connector, cable and 21-pin plug for connection to the head. An OBD-II diagnostic cable is used to connect diagnostic head to OBD-II diagnostic connector.

Hard & Intermittent Failures

A fault code is stored within the respective control module upon first occurrence of a fault in system being checked. CHECK ENGINE light will not be illuminated until completion of second consecutive driving cycle where previously faulted system is again monitored and a fault is still present or a catalyst damaging fault has occurred. If second drive cycle was not complete and specific function was not checked, PCM counts third drive cycle as next consecutive drive cycle. CHECK ENGINE light is illuminated if function is checked and fault is still present.

If an intermittent fault is present, and it does not cause a fault to be set through multiple drive cycles, 2 complete consecutive drive cycles with fault present are required for CHECK ENGINE light to be illuminated. Once CHECK ENGINE light is illuminated it will remain on unless specific function has been checked without fault through 3 complete consecutive drive cycles.

Fault code will also be cleared from memory automatically if specific function is checked through 40 consecutive drive cycles without fault being detected or with use of DIS Plus or GT-1 scan tool. To clear a catalyst damaging fault from memory, condition under which fault occurred must be evaluated for 80 consecutive cycles without fault reoccurring.

Readiness Code

Readiness code provides status (yes/no) of the system having completed all required monitoring functions or not. The readiness code is displayed with an aftermarket Scan Tool or the DISplus/GT-1. The code is a binary (1/0) indicating the following

1. 0 = Test not completed or not applicable - 6 cylinder vehicles (not ready - V8 and V12)
2. 1 = Test completed - 6 cylinder vehicles (ready - V8 and V12)

A readiness code must be stored after any clearing of fault memory or disconnection of PCM. A readiness code of "0" will be stored after a complete diagnostic check of all components/systems (that can turn on Malfunction Indicator Light) is performed. Readiness code was established to prevent anyone with an emissions related fault and a Malfunction Indicator Light on from disconnecting battery or clearing fault memory to manipulate results of emissions test procedure. Complete readiness code is equal to one byte (8 bits). Every bit represents one complete test and is displayed by scan tool

1. 0 = EGR monitoring (= 0, N/A with BMW)
2. 1 = Oxygen sensor heater monitoring
3. 1 = Oxygen sensor monitoring
4. 0 = Air condition (= 0, N/A with BMW)
5. 1 = Secondary air delivery monitoring
6. 1 = Evaporative system monitoring
7. 0 = Catalyst heating
8. 1 = Catalyst efficiency monitoring

Drive vehicle in such a manner that all tests listed above can be completed. When complete readiness code equals "1" (ready) then all tests have been completed and system has established its readiness.

Readiness code can be checked with DISplus/GT-1. This is helpful in verifying that drive cycle criteria was achieved. A repair can be confirmed before returning vehicle to customer by a successfully completed drive cycle. (Scheme 147)

SUMMARY

If no hard DTCs are present, driveability symptoms exist or intermittent DTCs exist, proceed to TROUBLE SHOOTING - NO CODES article for diagnosis by symptom (i.e., ROUGH IDLE, NO START, etc.) or intermittent diagnosis procedures.

CATALYST MONITORING

Efficiency of catalyst operation is determined by evaluating oxygen storage capability of catalytic converter using pre and post oxygen sensor signals. A correctly operating catalyst consumes or stores most of oxygen present in exhaust gas. To determine if catalyst is working correctly, signal of post cat oxygen sensor is evaluated over course of several pre-catalytic oxygen sensor oscillations. During evaluation period, signal of post-catalytic sensor must remain within a relatively constant voltage range.

Under normal closed loop operation, changing air/fuel ratio in exhaust gas results in lambda oscillations at pre-catalyst sensor. These oscillations are dampened by oxygen storage activity of catalyst and are reflected at post-catalyst sensor as a fairly stable signal. Depending on how vehicle is being operated at time of evaluation and type of catalyst or coating being used, signal may be in lean or rich voltage range.

CATALYST SENSOR MONITORING CONDITIONS

Scheme 148

Scheme 149

1. Catalyst Monitoring Based On Monitoring Oxygen Storage Capability - Engine closed loop feedback control generates lambda (air/fuel ratio) oscillations in exhaust gas. These oscillations are dampened by oxygen storage activity of catalyst. Amplitude of remaining lambda oscillations downstream of catalyst indicate storage capability.
2. Monitoring Procedure - To determine catalyst efficiency, a fixed number of complete lambda controller cycles (oxygen oscillation from upstream sensor) are used to calculate areas which are enclosed by controller cycle curve and is also calculated mean value. Average of all areas display magnitude of oxygen admission to catalytic converter. (Scheme 148) Magnitude of oxygen admission is used to calculate maximum permissible oscillation (areas of the cycle) of downstream sensor of a still good working catalyst. Then original measured oscillation (average of areas) from downstream sensor is compared to calculated maximum permissible value. A fault is detected if quotient (measured to calculated value) is greater than a fixed number. (Scheme 149)

Scheme 150

1. Catalyst Monitoring Based On Monitoring Oxygen Storage Capability - Engine closed loop feedback control generates lambda (air/fuel ratio) oscillations in exhaust gas. These oscillations are dampened by oxygen storage activity of catalyst. Amplitude of remaining lambda oscillations downstream of catalyst indicates storage capability. To determine catalyst efficiency, oscillation of upstream sensor is needed to calculate oxygen in and output (catalyst) by engine air mass and lambda-deviation. Downstream sensor signal for a threshold catalyst then is derived from this basic value. Anytime real sensor signal oscillation (downstream) corresponds to the model, a defective catalyst is recognized. (Scheme 150)
2. Monitoring Cycle - Monitoring cycle is represented by the following: Computation Of Efficiency Of Catalyst - Alternating current component of voltage of oxygen sensors before and after catalyst is determined, rectified and averaged. Actual quotient of oxygen sensor voltage before catalyst and voltage of oxygen sensor after catalyst is determined. Simultaneously, theoretical quotient of this voltage of oxygen sensors is computed in relation to operating point of engine. Respective operating point is determined using parameters load and engine speed. Fault Evaluation - At end of diagnostic period, number of stored values in adaptation matrix exceeding a limit is determined. If this number of stored values itself exceeds a threshold, a defective catalyst is evaluated. Check Of Monitoring Conditions - Monitoring principle is based on detection of relevant oscillations of downstream sensor signal during regular lambda control. It is necessary to check driving conditions for exceptions where no regular lambda control is possible. During such periods, and for a certain time afterward, computations of amplitude values and the following processing is interrupted, avoiding a distortion of monitoring information.

MISFIRE MONITORING

Misfire detection must determine if misfire is occurring, identify specific cylinder(s) and the severity of misfire, and whether it is emissions relevant or catalyst damaging. (Scheme 151) To do this, control module monitors crankshaft for acceleration losses during firing segments of each cylinder based on firing order. Process of misfire detection continues well after diagnostic drive cycle requirements have been completed. Misfire detection is ongoing and is only discontinued under certain conditions. See MISFIRE DETECTION DISABLING CONDITIONS table. (Scheme 152)- (Scheme 153).

MISFIRE DETECTION DISABLING CONDITIONS

Scheme 151

Scheme 152

Scheme 153

Scheme 154

Scheme 155

Scheme 156

1. General Description Measure Principle - Method of engine misfire detection is based on monitoring crankshaft acceleration. Engine roughness is derived from differences from segment periods (90 degree crank angle) durations which are corrected and compared to a load and engine speed dependent thresholds. Different statistical methods are used to distinguish between normal changes of segment duration and changes due to misfire. (Scheme 154) Segment periods are measured through an angular range of 90 degree crank angle. Segment starts 54 degrees before TDC. Beginning and end of segments are located at the same angle. Duration of crankshaft segments is measured continuously. (Scheme 154) Sensor Wheel Adaptation - To eliminate manufacturing tolerances and off-center installation, adaptation of sensor wheel tolerances is carried out during fuel cut off. Segment periods are corrected by adaptation values. With progressing adaptation, sensitivity of misfire detection is increasing. Calculation Of Engine Roughness Threshold Value - Engine roughness threshold value consists of base value, which is determined by a load/speed dependent map. During warm-up, base value is multiplied by a coolant temperature dependent correction value. Without sufficient sensor wheel adaptation, engine roughness threshold is limited depending on wheel tolerances expected.
2. Misfire Monitoring Structure - (Scheme 155)
3. Fault Processing Error Window - Within an interval of 200-1000 crankshaft revolutions, "error windows" to check for similar engine conditions are determined. Upon detection of misfire, window is extended if current operating point is not within window. Engine Operating Point Window - Engine operating window is updated with each segment without misfire. Misfire Detection (Emission Increase) - Within an interval of 1000 crankshaft revolutions (3000 segments) detected misfire events are added for each cylinder. If sum of all cylinder misfire incidents exceeds a predetermined value, a fault code is stored. If more than one cylinder is misfiring, all misfiring cylinders will be specified and individual fault codes for all misfiring cylinders and for multiple cylinders will be stored. Misfire Detection (Catalyst Damage) - Within an interval of 200 crankshaft revolutions, detected number of misfiring events is weighted and calculated for each cylinder. Weighting factor is determined by a load/speed dependent map. If sum of cylinder misfire incidents exceeds a predetermined value, a fault code is stored and MIL is illuminated. If cylinder selective count exceeds predetermined threshold, following measures take place: Lambda closed loop system is switched to open-loop. Cylinder selective fault code is stored. If more than one cylinder is misfiring, fault codes for all individual cylinders and for multiple cylinders will be stored. Fuel supply to respective cylinder is cut-off. (Scheme 156)

Scheme 157

Scheme 158

Scheme 159

1. General Description Measure Principle - Method of engine misfire detection is based on monitoring crankshaft acceleration. Engine roughness is derived from differences from segment periods (90 degree crank angle) duration which are corrected and compared to a load and engine-speed dependent thresholds. Different statistical methods are used to distinguish between normal changes of segment duration and changes due to misfire. (Scheme 157) Segment periods are measured through an angular range of 90 degree crank angle. The segment starts 54 degrees before TDC. Beginning and end of the segments are located at the same angle. Duration of crankshaft segments is measured continuously. Sensor Wheel Adaptation - To eliminate manufacturing tolerances and off-center installation, adaptation of sensor wheel tolerances is carried out during fuel cut-off. Segment periods are corrected by adaptation values. With progressing adaptation, sensitivity of misfire detection is increasing. Calculation Of Engine Roughness Threshold Value - Engine roughness threshold value consists of base value, which is determined by a load/speed dependent map. During warm-up, base value is multiplied by a coolant temperature dependent correction value. Without sufficient sensor wheel adaptation, engine roughness threshold is limited depending on wheel tolerances expected.
2. Misfire Monitoring Structure - (Scheme 158)
3. Fault Processing - (Scheme 159) Error Window - Within an interval of 200-1000 crankshaft revolutions, "error windows" to check for similar engine conditions are determined. Upon detection of misfire, window is extended if current operating point is not within window. Engine Operating Point Window - Engine operating window is updated with each segment without misfire. Misfire Detection (Emission Increase) - Within an interval of 1000 crankshaft revolutions (4000 segments), detected misfire events are added for each cylinder. If sum of all cylinder misfire incidents exceed a predetermined value, a fault code is stored. If more than one cylinder is misfiring, all misfiring cylinders will be specified and individual fault codes for all misfiring cylinders and for multiple cylinder will be stored. Misfire Detection (Catalyst Damage) - Within an interval of 200 crankshaft revolutions, detected number of misfiring events is weighted and calculated for each cylinder. Weighting factor is determined by a load/speed dependent map. If sum of cylinder misfire incidents exceeds a predetermined value, a fault code is stored and MIL is illuminated. If cylinder selective count exceeds predetermined threshold, following measures take place: Lambda closed loop system is switched to open-loop. Cylinder selective fault code is stored. If more than one cylinder is misfiring, fault codes for all individual cylinders and for multiple cylinders will be stored. Fuel supply to respective cylinder is cut-off.

Evaporative Emissions

Control of evaporative fuel vapors (hydrocarbons) from fuel tank is important for overall reduction in vehicle emissions. Evaporative system has been combined with ventilation of fuel tank, which allows tank to breathe (equalization). The overall operation provides

1. An inlet vent, to an otherwise "sealed" fuel tank, for the entry of air to replace the fuel consumed during engine operation.
2. An outlet vent with a storage canister to "trap and hold" fuel vapors that are produced by the expansion/evaporation of fuel in the tank, when the vehicle is stationary.

Canister is then "purged" using engine vacuum to draw the fuel vapors into the combustion chamber. This "cleans" the canister allowing for additional storage. Like any other form of combustible fuel, the introduction of these vapors on a running engine must be controlled. The ECM(s) control the evaporative emission valves which regulate purging of evaporative vapors.

On-Board Refueling Vapor Recovery (ORVR)

ORVR system recovers and stores hydrocarbon fuel vapor during refueling. Non-ORVR vehicles vent fuel vapors from the tank venting line back to the filler neck and in many states reclaimed by a vacuum receiver on the filling station fuel pump nozzle. When refueling, the pressure of the fuel entering the tank forces the hydrocarbon vapors through the tank refuelling breather hose to liquid/vapor expansion tank and into the active charcoal canister. HC vapors are stored in active charcoal canister and the system can then "breathe" through Diagnostic Module Tank Leakage (DM-TL) and air filter.

Scheme 160

Scheme 161

Scheme 162

Scheme 163

Scheme 164

Scheme 165

Scheme 166

Scheme 167

1. Evaporative System Leak Measurement - Evaporative system monitoring permits detection of leaks in evaporative system with a diameter of.019" (.5 mm) and up. Using a Diagnostic Module-Tank Leakage (DM-TL), an electrical actuated pump located at atmospheric connection of evaporative canister, a pressure test of evaporative system is performed in following order: During REFERENCE LEAK MEASUREMENT, electrical actuated pump delivers through reference restriction. Engine-management system measures pump electrical current consumption in this section. (Scheme 160) During LEAK MEASUREMENT, electrical actuated pump delivers through charcoal canister into fuel tank system. Pressure in evaporative system may be up to 25 kPa depending on fuel level in tank. Engine-management system measures pump electrical current consumption. A comparison of currents of reference leak measurement and leak measurement is a measure for leakage in tank. (Scheme 161) During PRESSURE TEST, purge valve needs to be shut. After test, canister purge is resumed and consequently the remaining pressure in the evaporative system is bled off. (Scheme 162)
2. Monitoring Structure Of Leak Measurement - (Scheme 163)and (Scheme 164).
3. Diagnosis Frequency & MIL Illumination - (Scheme 165)- (Scheme 166).
4. Evaporative Purge System Flow Check - Purge flow from charcoal canister through purge valve is monitored after coolant temperature has reached a fixed minimum value. The diagnosis is started during regular purging.
5. Monitoring Process Of Evaporative Purge System Flow Check Step 1 - For Rich Or Lean Mixture - Flow through purge valve is assumed as soon as the lambda controller is compensating for a rich or a lean shift. After this procedure, diagnosis is completed and evaporative purge system resumes working normally. (Scheme 167) Step 2 - For Stoichiometric Mixture Or First Step Fails - In this case, lambda controller does not need to compensate for a deviation. Therefore, after finishing regular purging, purge valve is opened and closed abruptly several times. Effect of additional cylinder charge triggers a variation of engine idle speed. If a predetermined value is reached, diagnostic procedure is completed. Step 3 - For Stoichiometric Mixture Or Second Step Fails - If threshold at second step is not reached, an additional procedure is performed. Purge valve is opened and idle air control valve simultaneously is closed to compensate idle speed increase. The effect is a decrease of measured idle air mass by mass airflow sensor. If a predetermined value is reached, diagnosis procedure is completed.

Scheme 168

Scheme 169

Scheme 170

Scheme 171

Scheme 172

Scheme 173

1. Evaporative System Leak Measurement - Evaporative system monitoring permits detection of leaks in evaporative system with a diameter of.039" (1.0 mm) and up. By means of a Diagnostic Module-Tank Leakage (DM-TL), a electrical actuated pump located at atmospheric connection of evaporative canister, a pressure test of evaporative system is performed in the following order: During REFERENCE LEAK MEASUREMENT, electrical actuated pump delivers through reference restriction. Engine management system measures pump electrical current consumption in this section. (Scheme 160) During LEAK MEASUREMENT, electrical actuated pump delivers through charcoal canister into fuel tank system. Pressure in evaporative system may be up to 25 kPa depending on fuel level in tank. Engine management system measures pump electrical current consumption. A comparison of currents of reference leak measurement and leak measurement is a measure for leakage in tank. (Scheme 161) During PRESSURE TEST, purge valve needs to be shut. After test canister purge is resumed, remaining pressure in the evaporative system is bled off. (Scheme 162)
2. Evaporative System Monitoring Structure - (Scheme 168)- (Scheme 169).
3. Diagnosis Frequency & MIL Illumination - see scheme 93- (Scheme 172).
4. Evaporative Purge System Flow Check - Purge flow from charcoal canister through purge valve is monitored after fuel system adaptation is completed and lambda controller is at closed loop condition. Diagnosis is started during regular purging. (Scheme 173)
5. Monitoring Cycle Of Evaporative Purge System Flow Check Step 1 - For Rich Or Lean Mixture - Flow through purge valve is assumed as soon as lambda controller is compensating for a rich or a lean shift. After this procedure, diagnosis is completed and evaporative purge system resumes working normally. Step 2 - For A Stoichiometric Mixture - In this case, lambda controller does not need to compensate for a deviation. Therefore, after finishing regular purging, purge valve is opened and closed abruptly several times. Effect of additional cylinder charge triggers a variation of engine idle speed. A predetermined value is reached if system functions properly and diagnosis procedure is completed. To start diagnosis function (step 2) several conditions have to be satisfied: Vehicle speed = 0. Engine at idle speed. Closed loop of lambda controller. Coolant temperature greater than a fixed limit. Furthermore, if diagnosis has already been started and one of the conditions has not been satisfied continuously, process will be interrupted and started again later. Engine idle speed variation less than a fixed limit.

SECONDARY AIR SYSTEM MONITORING

To reduce HC and CO emissions while engine is warming up, system uses a secondary air injection system. Immediately following a cold engine start, fresh air/oxygen is injected directly into the exhaust manifold. By injecting oxygen into exhaust manifold, warm up time of catalyst is reduced and oxidation of hydrocarbons is accelerated. Activation period of air pump can vary depending on engine type and operating conditions. See SECONDARY AIR SYSTEM MONITORING table.

SECONDARY AIR SYSTEM MONITORING

System components include electric air injection motor/pump, electric motor/pump relay, non-return valve, vacuum/vent valve, stainless steel air injection pipes, vacuum reservoir, vacuum reservoir check valve, and in-line resistor for speed control (V12 engine only).

Secondary air injection system is monitored via use of pre-catalyst oxygen sensor(s). Once air pump is active and is air injected into system, signal at oxygen sensor will reflect a lean condition. If oxygen sensor signal does not change within a predefined time, fault will be set and identify the faulty bank(s). If after completing the next cold start and a fault is again present, CHECK ENGINE light will be illuminated.

FUEL SYSTEM MONITORING

Fuel system monitoring is an OBD-II requirement which monitors calculated injection time in relation to engine speed, load, and the pre-catalytic converter oxygen sensor signals as a result of the residual oxygen in the exhaust stream. Engine control module uses the pre-catalyst oxygen sensor signals as a correction factor for adjusting and optimizing the mixture pilot control under all engine operating conditions.

Adaptation Values

To maintain an ideal air/fuel ratio, engine control module is capable of adapting to various environmental conditions encountered while the vehicle is in operation (i.e. changes in altitude, humidity, ambient temperature, fuel quality, etc.). Adaptation system can only make slight corrections and cannot compensate for large changes which may be encountered as a result of incorrect airflow or incorrect fuel supply to the engine.

Within areas of adjustable adaptation, engine control module modifies injection rate during idle and low load mid range engine speeds (additive adaptation) and during operation under a normal to higher load when at higher engine speeds (multiplicative adaptation). These values are displayed in DIAGNOSIS REQUESTS section of DIS software and is a helpful diagnostic tool that shows how system is trying to compensate for a less than ideal initial air/fuel ratio. See DIAGNOSIS REQUESTS table.

Note. If adaptation value is greater than 0.0 ms, engine control module is trying to enrichen mixture. If adaptation value is less then 0.0 ms, engine control module is trying to lean mixture.

DIAGNOSIS REQUESTS

Scheme 174

1. General Description - Fuel system monitoring includes lambda controller, restriction against limits for rich and lean and permanent deviation from mean position.
2. Monitoring Structure - If fuel system is suddenly hard disturbed (for example, a leaky injection valve) and therefore lambda controller reaches restriction (lean limit), a timer is started. Timer is incriminated as long as controller remains at limit. If timer exceeds a predetermined value, a fault for short trim will be detected and stored. For permanent deviation from mean position, there are additional lean and rich thresholds. If accumulated time (sum of all excesses for rich and lean) is greater than a fixed limit during a defined period, a fault for long term trim will be detected and stored. (Scheme 174)

OXYGEN SENSOR MONITORING

Note. Testing oxygen sensor should be performed using oscilloscope from PRESET MEASUREMENT list. If signal remains high (rich condition) check: fuel injectors, fuel pressure, ignition system, input sensors that influence air/fuel mixture, and engine mechanical. If signal remains low (lean condition) check: air/vacuum leak, fuel pressure, input sensor that influences air/fuel mixture, and engine mechanical. A mixture related fault code should be investigated first and does not always indicate a defective oxygen sensor. (Scheme 175)

Scheme 175

For oxygen sensor to operate correctly, sensor element must be heated. A non-operating heater will not allow sensor signal to reach its predefined maximum and minimum thresholds, resulting in delayed closed loop operation causing an impact on emission levels. As part of monitoring function for heater current and voltage, circuit is also checked for an open, short to ground and short to voltage, depending on values of current or voltage being monitored. See OXYGEN SENSOR MONITORING CONDITIONS table.

On Bosch systems, heater monitoring function measures both sensor heater current and the heater voltage in order to calculate sensor heater resistance and power. Oxygen sensor heater current is calculated via a voltage drop over a shunt resistor, internal to control module. If power of heater is not within a specified range, a fault will be set. Next time heater circuit is monitored and a fault is again present, CHECK ENGINE light will be illuminated. Heater function is monitored continuously while vehicle is in closed loop operation, as long as heater is activated by PCM. See OXYGEN SENSOR VOLTAGE OPERATING RANGE table.

On Siemens systems, if heater output is too low, signal amplitude of oxygen sensor will be reduced. If minimum low (rich) voltage and high (lean) voltage cannot be obtained within a predefined time, a fault will be set. Next time heater circuit is monitored and a fault is again present, CHECK ENGINE light will be illuminated. Heater function of pre-cat sensor is monitored continuously while vehicle is in closed loop operation, as long as heater is activated by PCM. See OXYGEN SENSOR VOLTAGE OPERATING RANGE table.

OXYGEN SENSOR MONITORING CONDITIONS

OXYGEN SENSOR VOLTAGE OPERATING RANGE

Oxygen Sensor Electrical Integrity Check

Monitoring electrical integrity of oxygen sensor is an ongoing functional check made under normal vehicle operation which pertains to faults with either the wiring, connectors, or sensor. If the monitored sensor voltage exceeds maximum threshold value, DME will interpret signal as a short to voltage. If the monitored sensor voltage is below the minimum threshold value the DME will interpret the signal as a short circuit or a short to ground. If the monitored voltage of the sensor remains unchanged or within a predetermined voltage range after the sensor has been heated and the engine temperature has exceeded a predefined threshold, the DME will interpret the signal as an open. (Separate fault code set - Siemens only). See OXYGEN SENSOR ELECTRICAL CHECK table.

OXYGEN SENSOR ELECTRICAL CHECK

Oxygen Sensor Heater Check

In order for the oxygen sensor to operate correctly the sensor element must be heated. An improperly/non operating heater will not allow the sensor signal to reach its predefined maximum and minimum thresholds which can result in delayed closed loop operation causing an impact on emission levels, or in increased emission levels while in closed loop operation. As part of the monitoring function for heater current and voltage, circuit is also checked for an open, short to ground and short to voltage depending on values of current or voltage being monitored.

On Bosch systems, heater monitoring function measures both sensor heater current and heater voltage in order to calculate sensor heater resistance and power. Oxygen sensor heater current is calculated via a voltage drop over a shunt resistor, internal to control module. If power of heater is not within a specified range, a fault will be set. The next time the heater circuit is monitored and a fault is again present, CHECK ENGINE light will be illuminated. Heater function is monitored continuously while vehicle is in closed loop operation, as long as the heater is activated by the Engine Control Module.

On Siemens systems, if heater output is too low, signal amplitude of oxygen sensor will be reduced. If predetermine minimum low (rich) voltage and high (lean) voltage can not be obtained within a predefined time, a fault will be set. Next time heater circuit is monitored and a fault is again present, CHECK ENGINE light will be illuminated. Heater function of pre-cat sensor is monitored continuously while the vehicle is in closed loop operation, as long as the heater is activated by the Engine Control Module.

Siemens Post-Catalyst Heater

Rear oxygen sensor heater is evaluated by monitoring the amount of change that occurs on rear oxygen sensor signal during deceleration/fuel cut-off phase. During deceleration phase, post-cat oxygen sensor is switched to a load resistance value of 100 kW (normal sensor resistance is 30 kW). By switching the resistance of the sensor to 100 kW, sensor voltage is expected to remain within a fixed range (lean). If heater is operating correctly, oxygen sensor signal will remain within a predefined voltage range.

System monitors number of cycles for which sensor voltage remains within fixed range (once per diagnostic cycle). If length of time sensor remains within fixed range is less then predetermined limit, fault will be set. During next drive cycle if heater circuit is monitored and a fault is again present, CHECK ENGINE light will be illuminated. Heater function is monitored once per trip while vehicle is in closed loop operation.

Scheme 176

Scheme 177

Scheme 178

Scheme 179

1. General Description - Response rate of upstream oxygen sensor is monitored by measuring period of lambda control oscillations. (Scheme 176)- (Scheme 177).
2. Diagnosis Procedure Of Monitor Sensor (Downstream) - Activity of monitor sensor after reaching operating conditions, is determined by 2 different procedures: Oscillation Check (Line Crossing) - If following checks are correct, monitor sensor will be regarded as okay: Monitor sensor signal (sensor voltage) is equal to or greater than nominal value of TV-correction and voltage increases, if lambda control goes to the lean side, or Monitor sensor signal (sensor voltage) is less than nominal value of TV-correction and voltage decreases, and if lambda control goes to rich side. Fuel Cut-Off Check - In addition to above mentioned checks, signal behavior of monitor sensor is checked in case of fuel cut-off. Therefore, monitor sensor voltage has to be below a given nominal value in case of fuel cut-off. If monitor sensor detected a defect, a fault code is stored and MIL is illuminated at next driving cycle.
3. Oxygen Sensor Heater Monitoring (Up & Downstream) General Description - For proper function of oxygen sensor, sensor element must be heated. A non-functioning heater delays sensor readiness for closed loop control and influences emissions. Monitoring function measures heater current for both sensors (voltage drop over a shunt) and heater voltage (heater supply voltage) to calculate sensor heater resistance. Monitoring function is activated once per trip if heater has been switched on for a certain time period and current has stabilized. (Scheme 178)
4. Oxygen Sensor Circuit Monitoring - Monitoring of electrical faults of sensors upstream and downstream of catalyst-not plausible voltages: Voltages exceeding maximum threshold are caused by a short circuit to voltage. Voltages falling below minimum threshold are caused by a short circuit of sensor signal or sensor ground to ECM ground. (Scheme 179)
5. If there is no plausible course of sensor voltage, an open circuit of sensor upstream catalyst can be detected if voltage remains in a specified range after sensor has been heated.

Scheme 180

Scheme 181

1. The response rate of the upstream oxygen sensor is monitored by measuring the period of the lambda control oscillations. (Scheme 176)- (Scheme 177). For diagnosis procedure of monitor sensor (downstream), activity of monitor sensor after reaching operating conditions is determined by 2 different procedures: Oscillation Check (Line Crossing) - If following checks are correct, monitor sensor will be regarded as okay. The monitor sensor signal (sensor voltage) is greater than or equal to the nominal value of the TV correction and voltage increases, or if lambda control goes to the lean side. Monitor sensor signal (sensor voltage) is less than nominal value of TV correction and voltage decreases, or if lambda control goes to the rich side. Fuel Cut-Off Check - In addition to above mentioned checks, signal behavior of monitor sensor is checked in case of fuel cut-off. Therefore, monitor sensor voltage has to be below a given nominal value in case of fuel cut-off. If monitor sensor is detected defective by OSCILLATION CHECK or FUEL CUT-OFF CHECK, a fault code is stored and MIL is illuminated at next driving cycle.
2. Oxygen Sensor Heater Monitoring (Up/Downstream) - For proper function of oxygen sensor, sensor element must be heated. A non-functioning heater delays sensor readiness for closed loop control and influences emissions. Monitoring function measures both sensor heater current (voltage drop over a shunt) and heater voltage (heater supply voltage) to calculate sensor heater resistance. Monitoring function is activated once per trip if heater has been switched on for a certain time and current has stabilized. (Scheme 180)- (Scheme 181).
3. Oxygen Sensor Circuit Monitoring - Monitoring of electrical faults of sensors upstream and downstream of catalyst. Implausible voltages are voltages exceeding the maximum threshold and are caused by a short circuit to voltage. Voltages falling below minimum threshold are caused by a short circuit of sensor signal or sensor ground to ECM ground. Implausible cause of sensor voltage is an open circuit if sensor upstream catalyst can be detected, or if voltage remains in a specified range after sensor has been heated.

Scheme 182

1. General Description Of Upstream Oxygen Sensor Monitoring - Both oxygen sensors upstream from catalyst are separately monitored for rich and lean voltage and response time (period monitoring and jump period monitoring). (Scheme 183)
2. Upstream Oxygen Sensor Monitoring Procedure - To determine switching time, lean and rich period times are added during a fixed number of lambda controller cycles. A malfunction is registered if one or both times exceed thresholds which depend on engine speed and load. (Scheme 182)
3. Monitoring Of Downstream Oxygen Sensors - Activity of monitor sensor after reaching operating conditions, is determined by an oscillation check of sensor signal (voltage). If conditions of following checks are fulfilled, monitor sensor is regarded to be in order. If monitor sensor detected a defect in these checks, a fault code is stored and MIL is illuminated at next driving cycle: Monitor sensor signal (sensor voltage) is greater or equal than a predetermined value at normal engine operating condition (normal combustion). Sensor voltage drops below a predetermined value during fuel cut-off conditions.
4. Oxygen Sensor Heater Monitoring - For proper function of the oxygen sensor, sensor element must be heated. A non-functioning heater delays sensor readiness for closed loop control and influences emissions. Monitoring function measures continuously both sensor heater current as well as heater voltage (heater supply voltage) to calculate sensor heater resistance. (Scheme 180)
5. Oxygen Sensor Circuit Monitoring - System monitors electrical faults of sensors upstream and downstream of catalyst: Not plausible voltages: Voltages exceeding maximum threshold are caused by a short circuit to voltage. Voltages falling below minimum threshold are caused by a short circuit of sensor signal or sensor ground to PCM ground. Not plausible course of sensor voltage: An open circuit of sensor upstream catalyst can be detected if voltage is remaining in a specified range after sensor has been heated. (Scheme 181)

Scheme 183

Scheme 184

Scheme 185

Scheme 186

1. Monitoring Upstream Oxygen Sensor - Both oxygen sensors upstream from the catalyst are separately monitored for rich and lean voltage and response time (period monitoring and jump period monitoring). (Scheme 183)
2. Monitoring Structure Of Upstream Oxygen Sensor - (Scheme 184)
3. Monitoring Procedure Of Upstream Oxygen Sensor; Overall Period Time Monitoring Of Upstream Oxygen Sensor - This determines the switching time the lean and rich period times are added during a fixed number of lambda controller cycles. A malfunction is registered if one or both of the times exceed the thresholds which depend on engine speed and load. (Scheme 185)- (Scheme 186).
4. Monitoring Procedure Of Downstream Oxygen Sensors (Rich To Lean Intake Mixture) - Lean sensor voltage is used to diagnose sensor activity. Therefore, this check is performed during deceleration fuel cut-off. Diagnosis starts after a calculated air mass (integral) is reached at transient from any operation mode to fuel cut-off mode and a defined time in deceleration fuel cut-off. Sensor voltage has to drop below a predetermined value otherwise a fault is detected and a code is stored.
5. Monitoring Procedure Of Downstream Oxygen Sensors (Lean To Rich Intake Mixture) - When diagnostic conditions at deceleration fuel cut-off are not fulfilled, diagnosis is carried out in opposite direction of oxygen sensor voltage. For a positive diagnosis result, signal must overrun a threshold after deceleration fuel cut-off. To ensure diagnosis, mixture can be short-term enriched, independent of respective operating conditions.
6. Oxygen Sensor Heater Monitoring - For proper function of oxygen sensor, sensor element must be heated. A non-functioning heater delays sensor readiness for closed loop control and influences emissions. Monitoring function measures continuously both sensor heater current as well as heater voltage (heater supply voltage) to calculate sensor heater resistance. (Scheme 180)- (Scheme 181).
7. Oxygen Sensor Circuit Monitoring - Monitoring electrical faults of sensors upstream and downstream of catalyst. Non-plausible voltages: Voltages exceeding maximum threshold are caused by a short circuit to voltage. Voltages falling below minimum threshold are caused by a short circuit of sensor signal or sensor ground to PCM ground. A non-plausible course of sensor voltage indicates an open circuit of sensor upstream catalyst can be detected if voltage is remaining in a specified range after sensor has been heated.