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

ENGINE PERFORMANCE & TRANSMISSION DIAGNOSTIC TROUBLE CODES TABLE

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General description

Catalyst monitoring is based on monitoring it's oxygen storage capability. The engine closed loop feedback control generates lambda (air/fuel ratio) oscillations in the exhaust gas. These oscillations are dampened by the oxygen storage activity of the catalyst. The amplitude of the remaining lambda oscillations downstream of the catalyst indicates the storage capability.

Catalyst monitoring is based on oxygen storage capacity.

The engine closed loop feedback control generates lambda (air/fuel ratio) oscillations in the exhaust gas. These oscillations are dampened by the oxygen storage activity of the catalyst. The amplitude of the remaining lambda oscillations downstream of the catalyst indicates the storage capability.

General Description of Leak Measurement

The evaporative system monitoring permits the detection of leaks in the evaporative system with a diameter of 0,5 mm and greater.

The Diagnostic Modul_Tank Leakage (DM-TL), an electrically actuated pump located at the atmospheric connection of the evaporative canister, performs a pressure test of the evaporative system in the following order

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1. During the Reference Leak Measurement, the electrically actuated pump delivers air through the reference restriction. The engine-management system measures the pump's electrical current consumption in this phase.
2. During the Leak Measurement, the electrically actuated pump delivers air through the charcoal canister to the fuel-tank system. The pressure in the evaporative system may be up to 25 hPa 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.
3. After the test the remaining pressure in the evaporative system is bled off through the charcoal canister by switching off the pump and solenoid.

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General Description of Secondary Air System Monitoring

At cold start the secondary air pump and valve are switched on for their normal operating function. The secondary air delivered into the exhaust gas creates a lean mixture that is indicated by the output voltage of the oxygen sensor.

Any time the oxygen sensor indicates a lean mixture within the maximum time for monitoring, a counter is incriminated by "one" up to a predetermined value.

This fixed limit corresponds to the minimum amount of secondary air (low-flow-limit-check).

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At cold start the secondary air pump and solenoid valve are switched on for their normal operating function. The secondary air delivered into the exhaust gas is measured by a separate (small) air mass flow sensor, which is mounted in the air tube between the secondary air pump and the secondary air filter.

Any time the air mass flow sensor indicates fixed min. or max. air mass values dependent on engine speed during a defined period, a fault will be detected.

The fixed min. air mass values correspond to the minimum amount of secondary air (low-flow-limit-check) produced by a defective pump.

The fixed max. air mass value corresponds to the maximum amount of secondary air (high-flow-limit-check) caused by leakage between the pump and the manifold.

In case the signal of the secondary air mass flow sensor is stuck, a fault will be detected.

By measuring a certain oscillation of the secondary air mass flow, it can be determined whether the secondary air valve is jammed open or blocked.

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The fuel system monitoring looks for permanent deviations of the A/F controller (lean and rich) from the mean position.

General Description of Upstream Oxygen Sensor Monitoring

Both oxygen sensors upstream of the catalyst are separately monitored for rich and lean voltage and response time (period monitoring and jump period monitoring).

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General Description of Oxygen Sensor Heater Monitoring

For proper function of the oxygen sensor, the sensor element must be heated. A non-functioning heater delays the sensor readiness for closed loop control and influences emissions.

The monitoring function continuously measures both the sensor heater current as well as the heater voltage (heater supply voltage) in order to calculate the sensor heater resistance.

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The Wide Range Air Fuel Ratio Sensor is ready for operation at a certain temperature. In most cases exhaust gas temperature is not sufficient for heating, so electrical heating is needed for the proper functioning of the sensor.

The diagnosis consists of three checks

Operational Readiness

Sensor readiness depends on heater performance. Thus the time delay between "heater on" and operational readiness is monitored. The readiness is checked at defined time ranges (dependent on engine coolant temperature) after the heater has been switched on.

Temperature Check

A second check is performed continuously. The sensor temperature is expected to remain within a predetermined range. Otherwise heater performance is not sufficient and a fault code is set.

Power Stage Diagnosis

During power stage on and off, the control signal (input) of the power stage is compared to its output signal. Also in the switched on condition heater current is checked against a minimum limit. With these checks, disconnection as well as short to either ground or battery voltage can be detected, and if appropriate, a fault code is set.

Monitoring Overview

Diagnosis of heater performance

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Dynamic Diagnosis (Slow Response)

The dynamic diagnosis runs at the same time as the catalyst diagnosis (conversion-efficiency). During catalyst and O2-sensor monitoring, the model-based nominal amplitude is modified to higher values.

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This results in an actual amplitude indicated by signal output of the sensor which is averaged over several lambda cycles (leanest A/F ratio minus richest A/F ratio). To enter into the calculation each measured value has to be within a predefined confidence interval (window).

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The max-value within the window is defined as amplitudes of a new, (normally operating) sensor. The min-value is defined as amplitudes of a limit (slow) sensor. This figure shows also the value of an actual amplitude of an functional sensor (in blue).

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After this follows the determination of the average of all measured actual amplitudes (e. g. N=4 valid amplitudes).

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The anticipated amplitude of a nominal sensor is compared with the measured actual amplitude and thereby standardized through the maximum possible deviation (amplitude of nominal sensor minus amplitude of a limit sensor).

diagnosis value= max. map (new sensor) - measured average value (actual amplitude)/max. map (new sensor) - min. map (slow sensor)

This method results in values for diagnosis, whereby 0 (zero) describes a new, normally operating sensor and 1 (one) a limit (slow) sensor.

Several values of diagnosis will be averaged and compared with the threshold. Exceeding the threshold results in a fault code being stored in the computers memory.

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Plausibility Check

1. If the A/F ratio of the upstream sensor is above a predetermined "lean" value and the signal of the downstream sensor indicates "high" voltage, a fault code is set.
2. If the A/F ratio of the upstream sensor is below a predetermined "rich" value and the signal of the downstream sensor indicates "low" voltage, a fault code is set

Offset Check

This monitoring looks for an incorrect lambda measurement due to shunting effects. If the lambda-offset of downstream-control exceeds a threshold, a fault code is set.

Heater Coupling Check

The heater of the O2-sensor is monitored for low impedance coupling between heater and sensor, which can cause lambda modulations with the heater pulse rate. If the difference of consecutive lambda values exceeds calibration, a fault code is set.

For proper function of the oxygen sensor, the sensor element must be heated. A non-functioning heater delays the sensor readiness for closed-loop control and influences emissions.

The monitoring function continuously measures both the sensor heater current as well as the heater voltage (heater supply voltage) in order to calculate the sensor heater resistance.

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1. ECM - controlled switching on of the sensor heater
2. one shunt for each sensor heater upstream and downstream of catalyst for current measurement

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