Diagnostic Trouble Codes with Test Charts: Other BMW 5 series E60/E61

Monitoring procedure

In order to determine the catalysts efficiency a fixed number of complete lambda controller cycles (oxygen oscillation from upstream sensor) are used to calculate the areas that are enclosed by the controller cycle curve and also calculate the mean value. The average of all areas is indicative of the magnitude of the oxygen admission to the catalytic converter.

Scheme 400

The magnitude of the oxygen admission is used to calculate the maximum permissible oscillation (areas of the cycle) of the downstream sensor of a still good working catalyst.

Scheme 401

Now the original measured oscillation (average of areas) from the downstream sensor is compared to the calculated maximum permissible value.

A fault is detected if the quotient (measured value to calculated value) is greater than the threshold value.

Scheme 402

In order to determine the catalyst's efficiency the model-based nominal amplitude of the upstream O2-sensor is modified to predefined higher values (forced stimulated).

This results in a known area of the A/F-controller, whereby the magnitude of the oxygen admission to the catalyst is equal independent of the driving conditions.

Scheme 403

The magnitude of the oxygen admission is used to calculate the maximum permissible oscillation (areas of the cycle) of the downstream sensor of a properly functioning catalyst.

A fixed number of complete lambda controller cycles are used to calculate the areas which are enclosed by the voltage of the downstream sensor and also to calculate the mean value.

Scheme 404

Now the original measured oscillation (average of areas) from the downstream sensor is compared to the calculated maximum permissible value.

A fault is detected if the quotient (measured value to calculated value) is greater than the threshold.

Scheme 405

Measurement Principle

The method of engine misfire detection is based on monitoring crankshaft acceleration.

The engine roughness is derived from the differences of the segment period (90°F crank angle) durations that are corrected and compared to load and engine-speed dependent thresholds. Different statistical methods are used to distinguish between normal changes of the segment duration and changes due to misfire.

Segment period measurement

Scheme 406

The segment periods are measured through an angular range of 90°F crank angle. The segment starts at 54°F before TDC. The beginning and end of the segments are located at the same angle. The duration of the crankshaft segments is measured continuously.

Sensor Wheel adaptation

To eliminate manufacturing tolerances and off-center installation the adaptation of the sensor wheel tolerances is carried out during fuel cut-off.

The segments periods are corrected by the adaptation values.

With progressing adaptation the sensitivity of misfire detection is improved.

Calculation of the engine roughness threshold value

The engine roughness threshold value consists of the base value, which is determined by a load/speed dependent map.

During warm-up the base value is multiplied by a coolant temperature dependent correction value.

Without sufficient sensor wheel adaptation the engine roughness threshold is limited depending on the wheel tolerances expected.

Scheme 407

Error Window

Within an interval of 200 and 1000 crankshaft revolutions "error windows" to check for similar engine conditions are determined. Upon detection of misfire the window is extended if the current operating point is not within the window.

Engine operating point window

The engine-operating window is updated with each segment without detected misfire.

Emission Increase

Within an interval of 1000 crankshaft revolutions (3000 segments) the detected misfire events are added for each cylinder. If the 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 the individual fault codes for all misfiring cylinders and for multiple cylinders will be stored.

Catalyst damage

Within an interval of 200 crankshaft revolutions the detected number of misfiring events is weighted and calculated for each cylinder. The weighting factor is determined using a load/speed dependent map.

If the sum of cylinder misfire incidents exceeds a predetermined value a fault code is stored and the MIL is illuminated at once.

If the cylinder selective count exceeds the predetermined threshold the following measures take place

1. the fuel control system is switched from closed-loop to open-loop operation
2. the cylinder selective fault code is stored
3. if more than one cylinder is misfiring the fault codes for all individual cylinders and for multiple cylinders will be stored
4. the fuel supply to the respective cylinder is cut-off

Scheme 408

Evaporative Purge System Flow Check

The purge flow from the charcoal canister through the purge valve is monitored after the fuel system adaptation is completed and the lambda controller is at closed-loop condition. The diagnosis is started during regular purging.

Monitoring Process of Evaporative Purge System Flow Check

Step 1 - For rich or lean mixture

Flow through the purge valve is assumed as soon as the lambda controller is compensating for a rich or a lean shift.

After this procedure the diagnosis is completed and the evaporative purge system resumes working normally.

Step 2 - For stoichiometric mixture or 1st step fails

In this case the lambda controller does not need to compensate for a deviation. Therefore, after finishing the regular purging, the purge valve is opened and closed abruptly several times.

The effect of additional cylinder charge triggers a variation of the engine idle speed.

If a predetermined value is reached the diagnosis procedure is completed.

Step 3 - For stoichiometric mixture or 2nd step fails

If the threshold at the 2nd step is not reached an additional procedure is performed. The purge valve is opened and the idle air control valve simultaneously is closed to compensate the idle speed increase. The effect is a decrease of the measured idle air mass by the mass airflow sensor.

If a predetermined value is reached the diagnosis procedure is completed.

Scheme 409

Monitoring Structure

If the fuel system is suddenly and significantly disturbed (e.g. by a leaky injection valve) and the A/F controller reaches its restriction or a permanent deviation from the mean position reaches the additional lean or rich thresholds and the 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 410

1. closed loop conditions
2. evaporative purge amount < below a defined percentage of lambda deviation

Upstream Oxygen Sensor Monitoring Procedure

To determine 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(s) the thresholds that are engine speed and load dependent.

Scheme 411

Monitoring of Downstream Oxygen Sensors

After reaching operating conditions, the activity of the monitor sensor is determined by an Oscillation Check of the sensor signal (voltage).

If the conditions of the following checks are fulfilled, the monitor sensor is considered to be functioning properly

1. The monitor sensor signal (sensor voltage) is greater or equal than a predetermined value at normal engine operating condition (normal combustion) or
2. The sensor voltage drops below a predetermined value during fuel cut-off conditions.

If a monitor sensor defect is detected in these checks, a fault code is stored and the MIL is illuminated at the next driving cycle.

Oxygen Sensor Circuit Monitoring

Monitoring of electrical faults of sensors upstream and downstream of catalyst

Not plausible voltages

1. ADC - voltages exceeding the maximum threshold VMAX are caused by a short circuit to VBatt
2. ADC - voltages falling below the minimum threshold VMIN are caused by a short circuit of sensor signal or sensor ground to ECM ground

Not plausible course of sensor voltage

An open circuit of the sensor upstream of the catalyst can be detected if the ADC - voltage is remaining in a specified range after the sensor has been heated

After reaching operating conditions, the activity of the monitor sensor is determined by an Oscillation Check of the sensor signal (voltage).

If the conditions of following checks are fulfilled, the monitor sensor is considered to be functioning properly

1. The monitor sensor signal (sensor voltage) is greater than or equal to a predetermined value at normal engine operating condition (normal combustion) or
2. The sensor voltage drops below a predetermined value during fuel cut-off conditions.

If a monitor sensor defect is detected during these checks, a fault code is stored and the MIL is illuminated at the next driving cycle.

Monitoring of electrical faults of sensors upstream and downstream of the catalyst

1. ADC - voltages exceeding the maximum threshold VMAX are caused by a short circuit to VBatt
2. ADC - voltages falling below the minimum threshold VMIN are caused by a short circuit of sensor signal or sensor ground to ECM ground

An open circuit of the sensor upstream of the catalyst can be detected if the ADC - voltage is remaining in a specified range after the sensor has been heated

Table of ECM Input/Output Signals

Engine Control Module (ECM)

ECM INPUT/OUTPUT SIGNALS REFERENCE

Transmission Control Module (EGS)

ECM INPUT/OUTPUT SIGNALS REFERENCE