Some useful info:
Getting that little Check Engine lights on your dash may seem a little discomforting. In reality it is really a miracle of engineering and computer technology. Instead of randomly pocking in vast amounts of wires, sensors, and mechanisms in such complex car as a Legend, this little light tells you that your computer knows exactly what is wrong with the car (most of the time).
That means the exact sensor or gate has been pin-pointed as being either partially disconnected or simply out of acceptable range.
Location of ECU on 1986-1990 Legends
The control unit is located under the passenger seat on sedans and under the passenger foot well carpet on the coupes.
The engine CPU is the form of an aluminum box with a little plexiglass window. All you have to observe is a little red LED.
Location of ECU on 1991-1995 Legends
On the 1991-1995 Acura/Honda Legends, you have to jump a service connector located on the passenger side right under the dashboard near the door. The connector has two pin inputs. Connecting them with something like a paper clip will force the check engine light on the dashboard to display the codes.
Extracting Codes
With the car either running or the key in the ON position, perform the necessary steps above and observe the blinking of the light. The light will blink displaying all the codes in sequence and then repeating them.
Reading Codes
The code numbers are read by counting the number of blinks between longer pauses. On 1986-1990 Legends, the code number is indicacted by a series of rapid LED blinks between longer pauses.
On 1991-1995 cars, codes 1-9 are indicated by a series of short flashes; two digit codes use a number of long flashes for the first digit followed by the number of short flashes for the second digit. So a code 43 will be represented by 4 long and 3 short flashes.
The position of codes in a sequence can be helpful in doing diagnostics. A display showing 1-1-1-pause-9-9-9 indicates two problems occurring at different times. A sequence showing 1-9-1-9-1-9 indicates two problems occurring at the same time.
Resetting ECU
Sometimes it may be useful to reset the ECU memory. Although that maybe done by removing the battery for around 20 minutes or so, this will also kill your clock and radio presets. A more elegant way is to:
on 86-90 Legends remove the alternator fuse for 20 seconds.
on 91-95 Legends remove the ACG fuse in the interior fuse panel for 20 seconds. (note that this will also clear the seat memory)
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Below are trouble codes for 86-95 Acura/Honda Legends:
1986-1990 Legend (G1)
Code # Explanation
1 Front Oxygen Sensor
2 Rear Oxygen Sensor
3 Manifold Absolute Pressure Sensor
5 Manifold Absolute Pressure Sensor
4 Crank Angle Sensor
6 Coolant Temperature Sensor
7 Throttle Angle Sensor
8 Top-Dead-Center Position Sensor
9 Number 1 Cylinder Piston Position
10 Intake Temperature Sensor
12 E.G.R. System
13 Atmospheric Pressure Sensor
14 Electronic Idle Control Module
15 Ignition Output Signal
17 Vehicle Speed Sensor
18 Ignition Timing Adjustment
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1991-1995 Legend (G2) (Click here for transmission trouble codes)
Code # Explanation
1 Left Oxygen Sensor
2 Right Oxygen Sensor
3 Manifold Absolute Pressure Sensor
5 Manifold Absolute Pressure Sensor
4 Crank Angle Sensor
6 Coolant Temperature Sensor
7 Throttle Angle Sensor
9 Number 1 Cylinder Position (No. 1 Sensor)
10 Intake Temperature Sensor
12 E.G.R. Sensor
13 Atmospheric Pressure Sensor
14 Electronic Idle Control Module
15 Ignition Output Signal
16 Fuel Injector
17 Vehicle Speed Sensor
18 Ignition Timing Adjustment
23 Left Knock Sensor
41 Left Oxygen Sensor Heater
42 Right Oxygen Sensor Heater
43 Left Fuel Supply System
44 Right Fuel Supply System
45 Left Fuel Metering
46 Right Fuel Metering
53 Right Knock Sensor
54 Crank Angle 2 Sensor
59 Number 1 Cylinder Position (No. 2 Sensor)
Getting that little Check Engine lights on your dash may seem a little discomforting. In reality it is really a miracle of engineering and computer technology. Instead of randomly pocking in vast amounts of wires, sensors, and mechanisms in such complex car as a Legend, this little light tells you that your computer knows exactly what is wrong with the car (most of the time).
That means the exact sensor or gate has been pin-pointed as being either partially disconnected or simply out of acceptable range.
Location of ECU on 1986-1990 Legends
The control unit is located under the passenger seat on sedans and under the passenger foot well carpet on the coupes.
The engine CPU is the form of an aluminum box with a little plexiglass window. All you have to observe is a little red LED.
Location of ECU on 1991-1995 Legends
On the 1991-1995 Acura/Honda Legends, you have to jump a service connector located on the passenger side right under the dashboard near the door. The connector has two pin inputs. Connecting them with something like a paper clip will force the check engine light on the dashboard to display the codes.
Extracting Codes
With the car either running or the key in the ON position, perform the necessary steps above and observe the blinking of the light. The light will blink displaying all the codes in sequence and then repeating them.
Reading Codes
The code numbers are read by counting the number of blinks between longer pauses. On 1986-1990 Legends, the code number is indicacted by a series of rapid LED blinks between longer pauses.
On 1991-1995 cars, codes 1-9 are indicated by a series of short flashes; two digit codes use a number of long flashes for the first digit followed by the number of short flashes for the second digit. So a code 43 will be represented by 4 long and 3 short flashes.
The position of codes in a sequence can be helpful in doing diagnostics. A display showing 1-1-1-pause-9-9-9 indicates two problems occurring at different times. A sequence showing 1-9-1-9-1-9 indicates two problems occurring at the same time.
Resetting ECU
Sometimes it may be useful to reset the ECU memory. Although that maybe done by removing the battery for around 20 minutes or so, this will also kill your clock and radio presets. A more elegant way is to:
on 86-90 Legends remove the alternator fuse for 20 seconds.
on 91-95 Legends remove the ACG fuse in the interior fuse panel for 20 seconds. (note that this will also clear the seat memory)
--------------------------------------------------------------------------------
Below are trouble codes for 86-95 Acura/Honda Legends:
1986-1990 Legend (G1)
Code # Explanation
1 Front Oxygen Sensor
2 Rear Oxygen Sensor
3 Manifold Absolute Pressure Sensor
5 Manifold Absolute Pressure Sensor
4 Crank Angle Sensor
6 Coolant Temperature Sensor
7 Throttle Angle Sensor
8 Top-Dead-Center Position Sensor
9 Number 1 Cylinder Piston Position
10 Intake Temperature Sensor
12 E.G.R. System
13 Atmospheric Pressure Sensor
14 Electronic Idle Control Module
15 Ignition Output Signal
17 Vehicle Speed Sensor
18 Ignition Timing Adjustment
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1991-1995 Legend (G2) (Click here for transmission trouble codes)
Code # Explanation
1 Left Oxygen Sensor
2 Right Oxygen Sensor
3 Manifold Absolute Pressure Sensor
5 Manifold Absolute Pressure Sensor
4 Crank Angle Sensor
6 Coolant Temperature Sensor
7 Throttle Angle Sensor
9 Number 1 Cylinder Position (No. 1 Sensor)
10 Intake Temperature Sensor
12 E.G.R. Sensor
13 Atmospheric Pressure Sensor
14 Electronic Idle Control Module
15 Ignition Output Signal
16 Fuel Injector
17 Vehicle Speed Sensor
18 Ignition Timing Adjustment
23 Left Knock Sensor
41 Left Oxygen Sensor Heater
42 Right Oxygen Sensor Heater
43 Left Fuel Supply System
44 Right Fuel Supply System
45 Left Fuel Metering
46 Right Fuel Metering
53 Right Knock Sensor
54 Crank Angle 2 Sensor
59 Number 1 Cylinder Position (No. 2 Sensor)
Please? 
