Trade 15 Automobile Electric

Trainee
Subject Area
Automobile Electric
15.2.1.21
1 - 19
Date:
1. Title of C.U.
: Motronic Systems IV
2. Subject / Class : Workshop Practice, 2nd Year of Training
3. Topics of
instruction
sections
: Adaption function
Diagnosis, trouble-shooting
Instructor
Subject Area
Automobile Electric
15.2.1.21
1 - 19
Date:
1. Title of C.U.
: Motronic Systems IV
2. Subject / Class : Workshop Practice, 2nd Year of Training
3. Topics of
instruction
sections
: Adaption function
Diagnosis, trouble-shooting
4. Previous
knowledge
: Basic design of Mono-Motronic system
Current, voltage and resistance measurements using
multimeter
Method of operation and handling of oscilloscope
5. Introduction
: If possible, Trainees should perform measurement exercises and
tests independently in groups.
For diagnosis and trouble-shooting, the Trainees should
independently locate and eliminate faults.
Specific Aims
Requirement Levels
Targets
The Trainee should:
- Be familiar with the principle of the adaption function
- Be able to describe the adaption function
- Be capable of checking and repairing a Mono-Motronic system
Knowledge
Ability
Resources
Time:
17 hours
Teaching Aids:
Demonstration equipment for Mono-Motronic, petrol engine with Mono-Motronic,
workshop oscilloscope, multimeter,
manufacturer's documentation on the Mono-Motronic systems studied
Instructor
Title of Curriculum Unit:
Motronic Systems IV
Trainee
15.2.1.21
2
Introduction
"Adaptive" sub-systems are important components of the electronic equipment used in motor
vehicles.
The term "adaptive" refers to a system which is capable of replacing stored pilot-control values with
substitute values calculated on the basis of actual operating conditions.
It is then not possible to make adjustments to such systems.
The adaption function is described here on the basis of Lambda control.
The control unit regulates the mixture composition by way of the injection quantity as a function of the
residual oxygen content (Lambda probe) of the exhaust gas. Pilot-control values are stored in the
control unit for this purpose. If, for example, the Lambda probe indicates that the mixture is too rich,
the "Lambda control" leans the mixture via the injection quantity.
The current basic setting is constantly corrected on the basis of intelligent feedback and the adaption
value stored in the electronic memory of the control unit.
An emergency-running program enabling the vehicle to be driven to the nearest garage despite the
failure of several signals is implemented in the event of a fault. Faults occurring whilst driving are
diagnosed, stored in the fault memory and interrogated in the course of service work.
Instructor
Title of Curriculum Unit:
Motronic Systems IV
1.
Trainee
15.2.1.21
3
Lambda control loop
1.1 Design and operation of the Lambda control loop
The function of the Lambda control is to keep the composition of the air/fuel mixture (10)
adjusted to the range around Lambda = 1, thus enabling the catalytic converter (4) to convert
the three harmful pollutant components carbon monoxide (CO) (2), hydrocarbons (HC) (1) and
nitrogen oxide (NOx) (3) into less harmful exhaust gases (7).
Oxygen
One of the effects of the pulsating action of the catalytic converter is that, in the case of exhaust
gas with a high oxygen content (lean mixture), oxygen is deposited on the surface of the catalytic converter where it can then be used in the subsequent low-oxygen phase (rich mixture) for
oxidative reactions.
The Lambda probe (6) in the exhaust gas flow continuously registers the oxygen content of the exhaust gas. If
the voltage value signalled to the control unit (5) is
greater than 450 mV, the mixture status is λ < 1. Lean
combustion (λ > 1) is assumed if the voltage value is
less than 450 mV.
The Mono-Motronic control unit processes the information received from the Lambda probe and
relays an appropriate manipulated variable to the injector (9) for adaption of the metered fuel
quantity (6). This control action has priority over the basic control of the mixture formation
system.
Instructor
Title of Curriculum Unit:
15.2.1.21
4
Motronic Systems IV
1.1.2 Block diagram of Lambda control loop
Injection signal
is shortened
Mixture is
leaned
Control unit
detects rich
mixture
Oxygen content of exhaust
gas increases
Lambda probe
voltage
Uλ = 0.2 V
Lambda probe
voltage
800 mV
Oxygen content of exhaust
gas decreases
Control unit
detects lean
mixture
Mixture is
enriched
Injection signal
is lengthened
The control cycle takes place several times per second.
Trainee
Instructor
Title of Curriculum Unit:
15.2.1.21
5
Motronic Systems IV
1.2
Trainee
Lambda control simulation
1.2.1 Design and operation of the Lambda control loop
Use an oscilloscope to investigate the influence of Lambda control on the injection signal.
Set the following engine operating data for this purpose:
Engine speed
in rpm
2000
Throttle-valve
position in °,
idle, full load
50
NTC/engine
in °C
NTC/air
in °C
Voltage at
Lambda probe
in V
80
30
Mid range
1.2.2 Connect up oscilloscope to injection
time measurement point, then
switch battery master switch off and
on again after several hours.
Note:
Injection time must then
be a constant 4.9 ms.
1.2.3 Slowly turn rotary knob for Lambda
probe voltage simulation back and
forth between 0.1 V and 0.9 V until
injection signal no longer fluctuates.
The injection time switches back
and forth between 3.2 and 6.6 ms.
lean
rich
Sim.
sensor
Instructor
Title of Curriculum Unit:
Trainee
15.2.1.21
6
Motronic Systems IV
1.3 Lambda control operation
Wear, unmetered air
Changes in air density
Fuel
Disturbance values
Injector
Engine
Lambda probe
Actuator
Controlled system
Sensor
Control unit
Injector actuation
pulse
Manipulated variable
Exh. gas
Probe signal
Control of basic
injection quantity
1 = Comparator
2 = Integrator
3 = Lambda correction factor
5 = Setpoint input
Controlled variable
Controller
3
2
1
Setpoint (approx. 450 mV)
Ref. input variable
5
The air/fuel mixture is regulated to λ = 1 by the integrator (2), which determines the variable
Lambda correction factor (3).
Instructor
Title of Curriculum Unit:
Motronic Systems IV
Trainee
15.2.1.21
7
If, for example, the air/fuel mixture drawn in is too lean (area (A) in bottom Fig.), the comparator (1) causes the integrator value and the Lambda correction factor to be increased in
stages until the Lambda probe signals "rich mixture" (area (B)). Following this voltage step
change, the mixture is first immediately altered by a certain amount to achieve mixture
correction as quickly as possible.
At the same time, the integrator
starts to shorten its "steps".
Manipulated variable adjustment is
performed during this period in line
with fixed values until a further
Lambda probe voltage step
change signals "lean mixture".
Thus, for example, the control
frequency can be matched to the
mixture throughput as a function of
engine speed.
U
V
Time
Injector actuation pulses
A
UI
V
B
0.8
λ <1
0.6
λ=1
0.4
λ >1
0.2
0
Time
Integrator
steps
Enrichment
128
Leaning
Lambda probe signal and integrator
Time
Instructor
Title of Curriculum Unit:
Trainee
15.2.1.21
8
Motronic Systems IV
1.4 Measurement of reference voltage
1.4.1 Switch off ignition and
Lambda probe connector.
Typen-Code
Type
code
λ - Code
λ code
Komb.
/AC
Comb.
/ AC
ACKlima
P/ N P/N
Distance
sig.
Wegsignal
AT
Procedure:
unplug
Voltage value: approx. 450 mV
EngineDrehzahl
speed
Fuel consumpVerbrauch
tion
Connect
up
voltmeter
(highimpedance) at the location shown in
the adjacent circuit diagram.
Switch ignition on again.
Throttle-valve
actuator
Drosselklappensteller
Relais für
Intake-manifoldSaugrohrheizung
heater relay
Measurement point for reference voltage
1.4.2 Function of voltage measured at pin
28:
The voltage value measured corresponds to the reference voltage at
the comparator. With an OPEN
LOOP, it acts as substitute voltage
and prevents integrator fluctuation. In
this mode, fuel metering is only implemented by way of open-loop control.
Note:
The Mono-Motronic control unit has a
separate negative connection for
evaluation of the Lambda probe
signal voltage to keep earth free of
disturbance voltages.
5V
450 mV
>450 mV
= rich
to
integrator
<450 mV
= lean
Negative
wire for
Lambda
control loop
Configuration of connections 11 and 28 at MonoMotronic control unit
Instructor
Title of Curriculum Unit:
15.2.1.21
9
Motronic Systems IV
1.5
Trainee
Representation of control action with a diagnosis program (recorded on a demonstration model)
and description of the processes involved
Measured values
A comparator in the Mono-Motronic
control unit constantly compares the
Lambda probe voltage signal to a
reference voltage stipulated by the
manufacturer. This threshold value is
between 450 and 500mV.
As long as the Lambda probe signal
voltage is less than the reference
voltage, the voltage signal at the
comparator output is high. In this control status, the value of the Lambda
integrator moves towards "mixture
enrichment", as the slowly increasing
integrator voltage constantly extends
the injection time.
%
Lambda-Integrator
Volts
Lambda probe voltage
Slow enrichment by way of the integrator results in smoother engine running.
The ultimate effect of mixture enrichment is that - following an engine-related response
time (governed by load and engine speed) - the Lambda probe supplies a voltage which is
higher than the reference voltage. Consequently, the comparator output voltage drops to
0 volts.
Monitoring
λ-probe signal
Reference voltage
Integrator
Lambda shift
Comparator
Instructor
Title of Curriculum Unit:
Motronic Systems IV
15.2.1.21
10
λ control loop timing diagram
As optimum emission values are obtained with a slightly richer mixture, a signal shift
specified by the so-called shift time is implemented in the controller. This results in the
control continuing to move towards "rich", although the Lambda probe is already
detecting a rich mixture. The Lambda integrator does not change direction to lean the
mixture until the shift time has been completed.
Lambda probe signal
Comparator signal
Shift time
Integrator
actuation signal
Integrator voltage
Shift time ts
Trainee
Instructor
Title of Curriculum Unit:
Trainee
15.2.1.21
11
Motronic Systems IV
1.6 Determination of Lambda control adjustment range
Use an oscilloscope (or diagnosis program) to establish the limits of the injection time
adjustment range as a function of the Lambda probe signal.
Set the following engine operating data:
Engine speed
in rpm
2000
Throttle-valve
position in °,
idle, full load
50
NTC/engine
in °C
NTC/air
in °C
Voltage at
Lambda probe
in V
80
30
Mid range
Switch battery master switch off and
on again after several seconds.
Slowly turn rotary knob for Lambda
probe voltage simulation first towards
"rich" and then towards "lean".
Type code
Connect up oscilloscope as shown in
adjacent circuit diagram.
Fuel
pump
Intake-manifold
heater relay
ACF pulse valve
Measured injection times:
Lambda probe signal
Injection time
in ms
Rich
3.2
Lean
6.6
The Lambda control adjustment range for this operating point is:
6.6 ms - 3.2 ms = 3.4 ms
Injector
Instructor
Title of Curriculum Unit:
Motronic Systems IV
Trainee
15.2.1.21
12
1.7 Lambda control loop adaption process
1.7.1 Examine mixture adaption and
Lambda control adaption on the basis
of the simulated occurrence of
unmetered air downstream of the
throttle valve.
The basic mixture becomes too lean,
as the metered fuel quantity is fixed
as a function of throttle valve position
and engine speed.
The mixture control system is not
able to provide compensation for the
presence of unmetered air.
1.7.2 Circuit diagram with oscilloscope
symbol for recording injection time
with an oscilloscope.
1.7.3 Use test leads to connect up the oscilloscope to the specified measurement points.
Unmet. air
Instructor
Title of Curriculum Unit:
Trainee
15.2.1.21
13
Motronic Systems IV
1.7.4 Set the engine operating data as specified below:
Engine speed
in rpm
2000
Throttle-valve
position in °,
idle, full load
40
1.7.5 Switch off ignition switch and battery
master switch and then switch both
on again in reverse order.
NTC/engine
in °C
NTC/air
in °C
Voltage at
Lambda probe
in V
80
30
Mid range and
connector pin 28
unplugged
5
V
cm
The oscilloscope must then display
the oscillogram shown.
1
ms
cm
1
ms
cm
Lambda control limit
1.7.6 Then plug connector back in between
pin 28 of control unit and Lambda
probe.
Carefully turn potentiometer for
Lambda probe voltage simulation
anti-clockwise (in "rich" direction), so
that injection time is extended and
approaches the enrichment control
limit in a pulsating manner.
5
V
cm
The control limit is shown by a broken
line in the adjacent oscillogram.
Due to the fact that the simulation signal constantly indicates a lean mixture and the Lambda
probe keeps attempting to enrich the mixture still further, the Lambda control moves towards
the control limit.
The injection time on reaching the control limit is 7.7 ms.
Instructor
Title of Curriculum Unit:
15.2.1.21
14
Motronic Systems IV
1.7.7 Leave the potentiometer in the same
setting as in 1.7.6 and continue to
observe the injection signal for
roughly one minute.
5
Trainee
V
cm
Observation:
The ti-signal briefly dwells at the
control limit (6.2 ms) and is then
extended in small steps to
approx. 7.7 ms.
1
By further increasing the integrator voltage, the controller attempts to enrich the mixture
such that the Lambda probe signal can switch back to 0.9 mV.
The integrator voltage/correction factor cannot be reversed as the simulator voltage
constantly indicates too lean a mixture.
This process is illustrated by the diagram below.
Leaning
Enrichmt.
Integrator
steps
Time
ms
cm
Instructor
Title of Curriculum Unit:
Motronic Systems IV
Trainee
15.2.1.21
15
The simulation implemented would result in a large quantity of unmetered air, for
which the system would not be able to provide compensation.
The fault "Control limit reached" would be stored in the fault memory.
Given a smaller volume of unmetered air, the controller can enrich the mixture to the extent
required to permit a change in integrator voltage. This situation is illustrated below.
Leaning
Enrichmt.
Integrator
steps
Time
If, however, Lambda = 1 is to be maintained, the integrator voltage can no longer fluctuate
around its ideal value. This could be achieved by increasing the basic injection quantity.
For this reason, modern injection systems are equipped with adaptive control loops.
The system control unit thus incorporates a so-called adaption block with a non-volatile
memory which is also able to influence the injection time.
The purpose of this is to keep the integrator fluctuating as far as possible around its
mean value of 128.
Instructor
Title of Curriculum Unit:
Motronic Systems IV
Trainee
15.2.1.21
16
Lambda control with adaption block
Fuel
Changes in air density:
Disturbance values
Injector:
Actuator
Exh. gas
Engine:
Controlled system
Lambda probe:
Sensor
Control unit
Injector actuat. pulse:
Manipulated variable
Control of basic
injection quantity
Controller
Probe signal:
Controlled variable
Setpoint
(approx. 450 mV):
Refer. input variable
Adaption block
If, for example, the Lambda probe signals too lean a mixture over a lengthy period due to
unmetered air in the exhaust, the Lambda control attempts to provide compensation by means
of continuous enrichment. If the air/fuel mixture is still too "lean" on reaching the control limit,
the adaption block intervenes in the fuel metering process by slowly extending the injection
pulses step by step until the Lambda probe signals "rich mixture" and the integrator value
can be reduced again to permit fluctuation around the mean level.
The correction values required for this additional enrichment are stored in the non-volatile
memory of the adaption block and are immediately available on re-starting the engine.
The process described is referred to as adaption and is an example of automatic optimisation
of the Lambda control system or "adaptive control".
All the stored values are lost on disconnecting the battery, which means that the
"adaption process" has to re-commence next time the engine is started again after this.
Problems may be encountered when performing trouble-shooting at the workshop on vehicles
fitted with adaptive control systems, as the vehicle performance alone can no longer provide
an indication of the faults occurring on account of these being masked by the adaptive control
systems.
Modern computer-controlled testers enable the adaption memories to be read out via
a serial interface.
Instructor
Title of Curriculum Unit:
Motronic Systems IV
2.
Diagnosis
2.1
Read out flash code without diagnosis tester (VAG 1551, Bosch KTS 300).
15.2.1.21
17
Test requirements:
Control unit positive and negative power supply OK
Connections to diagnosis sockets OK
-
Top left: Positive from terminal 15
Bottom left: Negative
Top right: K-wire from pin 22
Bottom right: L-wire from pin 23
Wire fitted at pin 33 and OK
1 = Evaluation unit
(or alternatively diode test
lamp and switch)
4 = Control unit
5 = Test lead
ATTENTION:
Do not disconnect control unit plug or battery, as this would erase fault memory.
Faults are stored under the following conditions:
- In the course of test drive of at least 10 minutes duration or, if engine will not run,
- operate starter for at least 6 seconds and
- leave ignition switched on
Memory capacity: Up to 10 faults
Fault code 0203 (flash code 2113) is displayed with ignition on and self-diagnosis
activated. This is OK as no Hall pulses are being applied. No fault has occurred.
Flash code readout
Switch on ignition or allow engine to idle
Press button for at least 4 seconds (or actuate switch)
Diagnosis lamp starts to flash
Each flash code consists of 4 flash pulse groups
Each group has 1, 2, 3, 4 flash pulses with intervals of approx. 2.5 seconds
Example: II INTERVAL III INTERVAL IIII INTERVAL II (flash code 2342)
Trainee
Instructor
Title of Curriculum Unit:
Motronic Systems IV
End of diagnosis:
Switch off ignition or increase engine speed to >2500 rpm.
Erasing fault memory:
With ignition switched off, press and hold button on tester.
Switch on ignition and release button after at least 5 s.
Note:
Keep to fixed sequence
1. Stimulate and read out flash code
2. Perform actuator diagnosis (with KTS 300)
3. Erase fault memory
Flash code
Flash code
1232
2113
2121
2121
2212
2312
2322
2342
2341
2413
1111
4444
Fault
Throttle-valve actuator
Signal implausible
Hall signal
No signal
Idling-speed switch
Closed
Idling-speed switch
Open
Throttle-valve potentiometer
Short to earth
Open circuit, short to positive
Open circuit, short to earth
Short circuit in track 1/2
Engine-temperature sensor
Open circuit, short to positive
Short to earth
Signal implausible
Intake-air temperature sensor
Open circuit, short to positive
Short to earth
Lambda probe
Open circuit
Short to earth
Short to positive
Lambda control
Rich stop
Lean stop
Altitude adaption
Outside max. range
Outside min. range
Control unit (digital section/computer)
Defective
No fault stored
Trainee
15.2.1.21
18
Instructor
Title of Curriculum Unit:
Motronic Systems IV
Trainee
15.2.1.21
19
2.2 Fault diagnosis using system tester
Precise checking and basic setting of the system (e.g. ignition timing) is only possible
using the system tester of the manufacturer.
For Audi/VW this is the VAG 1551.
Faults occurring in the injection and ignition system are stored in a non-volatile memory.
These include problems with the control unit, sensor and actuator faults, open circuits in
wiring and short circuits, as well as incorrect information from the sensors.
Data relating to the following specific components/sensors and their wiring are stored:
Control unit
Idling-speed switch
Throttle-valve actuator
Throttle-valve potentiometer
Air-temperature sensor
Coolant-temperature sensor
Hall sender
Lambda probe
Lambda control with minimum and maximum control stop and
Upper/lower adaption limit exceeded/not reached
Actuator diagnosis can be used to test the following components:
Throttle-valve actuator (stem is retracted and extended)
ACF pulse valve (clicks)
Intake-air preheating relay (clicks)
It is thus possible to achieve rapid assessment and diagnosis of the engine-management
system with little test and measuring equipment outlay.
Diagnosis is implemented in system tester function 02 and the actuator test in function 03.
Actuator diagnosis can only be performed with the engine stopped and the ignition
switched on.
Wherever possible, the fault memory is to be interrogated with the engine running (refer to
the appropriate Workshop Manual for details).
The memory must always be erased following fault rectification.
Faults relating to the Lambda control function can only be interrogated after a test drive of
at least 10 minutes' duration. Temporary faults such as an open circuit in the wiring or
loose contacts are also stored. If these do not re-occur after 10 engine starts they are
erased automatically.
In the past, changes in ambient or engine operating conditions (engine wear, air density,
leaks etc.) made basic setting (CO content, idling speed) necessary.
Adaptive systems are capable of recognising and adapting to changes in ambient and
operating conditions, thus obviating the need for Mono-Motronic idling-speed and
CO adjustment.
The basic setting function (04) of the tester 1551 deactivates the digital idling-speed
stabilization (DIS) and permits basic distributor setting with the engine running.
The ignition timing should be checked at an oil temperature of at least 80 °C.