Self-diagnosis system for a motor vehicle

Various detectors are provided for detecting engine operating conditions and for continuously producing an operating condition signal during operation of an engine. A self-diagnosis device is responsive to the operating condition signal for detecting an abnormality in the signal and for producing a data signal. A nonvolatile memory is provided for storing the data signal. The data signal is indicated on a display on an outside computer.

BACKGROUND OF THE INVENTION 
The present invention relates to a self-diagnosis system for a motor 
vehicle. 
Recently, a motor vehicle has been equipped with an electronic control 
system for controlling various components of an engine, such as fuel 
injectors, thereby improving driveability, exhaust gas emission, fuel 
consumption, and engine power. The electronic control system controls the 
components based on information represented by output signals from various 
sensors for detecting engine operating conditions. Accordingly, if 
malfunctions of components and sensors occur, the engine does not properly 
operate. 
However, because of the complexity of the electronic control system, it is 
difficult to immediately find out the trouble. Accordingly, a 
self-diagnosis device for easily checking the electronic control system 
should be provided in the motor vehicle. 
Japanese Patent Application Laid Open 59-24270 discloses an electronic 
control system provided with the self-diagnosis system where signaling 
lamps provided on the vehicle are lit or flashed to indicate a trouble 
code representing a defective part in the control system when 
abnormalities occur in sensors and actuators such as injectors. Data of 
the troubles are written in a backup random-access memory (RAM) at a 
predetermined address, which is provided in the electronic control system. 
A diagnostician in an auto shop reads out the trouble code indicated by 
lamps or a display of a computer which is connected to the vehicle. Thus, 
information on the trouble is recognized by the diagnostician so that the 
defective parts such as sensors and switches can be appropriately 
repaired. 
However, in the conventional diagnosis system, an abnormality which occurs 
only under a particular driving condition which can not reoccur in the 
auto shop can not be diagnosed in the shop. Thus, the repair is 
troublesome and in some cases, the cause of the abnormality cannot be 
thoroughly explained. 
SUMMARY OF THE INVENTION 
The object of the present invention is to provide a self-diagnosis system 
where an abnormality which cannot reoccur in the shop is easily detected, 
thereby enabling an immediate and precise repair of the vehicle. That is, 
it is very difficult at the auto shop to repeat the same condition by 
which the abnormality occurred in the past. 
According to the present invention, there is provided a self-diagnosis 
system for a motor vehicle comprising detector means for detecting engine 
operating conditions and for producing an operating condition signal 
during operation of an engine, an engine control data calculator 
responsive to the operating condition signal for producing an engine 
control signal, self-diagnosis means responsive to the operating condition 
signal and to the engine control signal for detecting an abnormality in 
both the signals and for producing a data signal including a location of 
trouble, a nonvolatile memory for storing the data signal, and output 
means responsive to an input signal for producing an output signal 
representing the stored data signal. 
The other objects and features of this invention will become understood 
from the following description with reference to the accompanying drawings 
.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
An automobile is equipped with an electronic control system 1 for 
controlling various components of an engine. Referring to FIG. 1, the 
electronic control system 1 comprises a central processor unit (CPU) 5, a 
random access memory (RAM) 9, a read only memory (ROM) 8, a nonvolatile 
random access memory (RAM) 10, an input interface 6 and an output 
interface 7. These CPU 5, RAM 9, RAM 10, ROM 8, and input and output 
interfaces 6 and 7 are connected to each other through a bus line 11. 
Programs and data for controlling the engine and fixed data such as 
trouble codes representing trouble data and trouble location are stored in 
the ROM 8. The RAM 10 is to store trouble data codes and the trouble 
location of codes. 
The input interface 6 is applied with a coolant temperature signal Tw from 
a coolant temperature sensor 15, an air-fuel ratio feedback signal 
.lambda. from an O.sub.2 sensor 16, an intake-air quantity signal Q from 
an intake manifold quantity sensor 12, a crank angle signal O from a crank 
angle sensor 13, and an engine speed signal N from an engine speed sensor 
14. The sensors 12 to 16 and other sensors and switches (not shown) form 
an operating condition (engine parameter) detecting means 2. These signals 
from the sensors and switches are temporarily stored in the RAM 9 after 
processing the data in the CPU 5. The CPU 5 produces control signals, 
which are applied through the output interface 7 to an engine operating 
means 3. The engine operating means 3 comprises a driver 17 and fuel 
injectors 18 for controlling the air-fuel ratio of the engine. 
The CPU 5 further sends a signal through the output interface 7 to a 
warning means 4 having a driver 19 and warning lamps 20. When an 
abnormality is detected in the system 1 by self-diagnosis function, a 
corresponding trouble code is read out from the ROM 8 so as to turn on or 
flash the warning lamps 20, thereby indicating the trouble code. 
An outside diagnosis device 21 having a display 21a is detachably connected 
with the input interface 6 and output interface 7 of the control system 1. 
The diagnosis device 21 is operated by a diagnostician so that the 
calculated data on engine operating conditions which are stored in the RAM 
9 and trouble codes stored in the nonvolatile RAM 10 are indicated on the 
display 21a. 
The control system 1 is described more in detail with reference to FIG. 2. 
The control system 1 is provided with a self-diagnosis means 24, to which 
output signals of the engine operating condition detecting means 2 and 
output signals of a engine control data calculator 22 are applied. The 
calculator 22 calculates engine control data such as fuel injection pulse 
width and ignition timing in dependency on the operating conditions. A 
pulse width duty signal and an ignition signal from the calculator 22 are 
applied to the engine operating means 3 through a control signal output 
means 23. 
When an abnormality is detected in dependency on the output signals of the 
engine operating condition detecting means 2 and the calculator 22, a 
trouble data signal is applied to the ROM 8 from which a trouble code 
representing defective parts and conditions of the trouble are read out. 
The trouble codes retrieved from the ROM 8 and data on operating 
conditions at the time when the trouble occurred, which are temporarily 
stored in the RAM 9, are sequentially stored at predetermined addresses in 
the nonvolatile RAM 10 as shown in FIG. 4. Furthermore, the self-diagnosis 
means 24 applies a trouble code signal, dependent on the trouble code 
stored in the RAM 10 to the warning means 4 through a trouble code output 
means 25 so as to indicate the trouble code by flashing the warning lamps 
20. 
When the outside diagnosis device 21 is connected to the control system 1 
and a trouble data demand signal is applied thereto, the trouble code and 
operating condition data stored in the nonvolatile RAM 10 are applied to 
the diagnosis device 21 through a data output means 26 to alternately 
indicate the trouble code and operating condition data on the display 21a. 
The diagnoses device 21 and the data output means 26 comprise a trouble 
code display means. 
The operation of the system is described hereinafter with reference to the 
flowchart of FIG. 3. During the running of the engine, the control system 
performs a main routine of a control program for controlling air-fuel 
ratio and ignition timing. During the main routine, an interrupt request 
signal is applied to the self-diagnosis means 24 at every predetermined 
cycle, so that the following self-diagnosis program is performed. 
At a step 101, data necessary for the self-diagnosis is read out from the 
engine operating condition detecting means 2 and at a step 102, the 
self-diagnosis dependent on the data is performed in the self-diagnosis 
means 24. At a step 103, it is determined whether there is an abnormality 
in the control system. When there is an abnormality, the program goes to a 
step 104 where a trouble code representing the defective parts which 
causes the abnormality in the control system 1 is retrieved from the ROM 8 
and stored in the nonvolatile RAM 10. At a step 105, data on the operating 
conditions, of which the trouble has occurred, is read out from the RAM 9 
and also stored in the nonvolatile RAM 10. At a step 106, the trouble code 
is indicated by flashing the warning lamps 20. 
At a step 107, it is determined whether a trouble data demand signal is 
applied to the control system 1 from the outside diagnosis device 21. When 
the demand signal is not applied, the program returns to the main routine. 
On the other hand, when the demand signal is applied, the trouble code 
data and the operating condition data stored in the RAM 10 are fed to the 
diagnosis device 21 through the data output means 26 at a step 108. The 
operating condition signal in the form of binary digit is converted into a 
decimal digit. Consequently, the trouble code and operating condition data 
are indicated on the display 21a by turns. Thus, the diagnostician 
confirms the defective part and the condition of the trouble corresponding 
to the indicated code in accordance with an instruction manual. At the 
same time, the trouble can reoccur in dependency on the operating 
condition data so that the control system can be accurately repaired. When 
it is determined that there is no abnormality at the step 103, the program 
proceeds directly to the step 107. 
FIGS. 5 and 6 show a modification of the control system 1 of the present 
invention. In the aforementioned system, data of operating conditions 
(engine parameter) upon trouble are stored in the RAM 10. In the 
modification, various diagnosing data used to determine an abnormality in 
the control system 1 are stored in the nonvolatile RAM 10 at a step 105a 
instead of data on the operating conditions as shown in FIG. 6. Namely, 
when abnormality is detected in the course of self-diagnosis program, the 
diagnosing data used in the diagnosis as well as the trouble code are 
stored in the predetermined addresses of the nonvolatile RAM 10 (steps 104 
and 105a). 
In accordance with the present invention, even in a case of an abnormality 
which can not reoccur in an auto shop, since the engine operating 
conditions under which abnormality has actually occurred are shown, the 
cause of the abnormality is easily discovered. Consequently, the 
abnormality can be properly repaired in a short time. 
While the presently preferred embodiments of the present invention have 
been shown and described, it is to be understood that this disclosure is 
for the purpose of illustration and that various changes and modifications 
may be made without departing from the scope of the invention as set forth 
in the appended claims.