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Home >> Acura >> 1990 >> Legend Base, 4D Sedan, Automatic >> Repair and Diagnosis >> Engine Performance >> System >> Engine Controls - Tests W/Codes >> Self-Diagnostic System >> Retrieving Codes
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Retrieving Codes

Locate ECU and check for trouble codes. See ELECTRONIC CONTROL UNIT (ECU) LOCATION  table. Pull down ECU inspection window located under passenger's front seat (on Legend Sedan). Turn ignition on and observe Red LED on top of ECU. LED indicates a system failure code by number of blinks.

The LED indicates component problems with a blinking series of codes. Trouble codes 1-9 are indicated by individual short blinks. Codes 10-43 are indicated by a series of long and short blinks. One long blink equals 10 short blinks. Add long and short blinks together to determine trouble code.

If codes other than those listed are indicated, substitute a known good ECU and recheck. If codes do not reappear, replace original ECU. It is possible for CHECK ENGINE light and Red LED to come on indicating a system problem, when in fact there is a poor or intermittent connection. Check all related connections and repair as necessary. Whenever CHECK ENGINE light comes on and Red LED stays on steady, replace ECU.

ELECTRONIC CONTROL UNIT (ECU) LOCATION

Application Location
Legend Coupe Below Carpet Under Passenger's Side of Dash
Legend Sedan Under Passenger's Front Seat
NOTE: Before starting tests, ensure engine is in good mechanical condition and adjusted to specifications.
TROUBLE CODE IDENTIFICATION CHART (1)

Code System Affected Probable Cause
0  ECU No Signal To ECU
1  Oxygen Sensor (Front) Open/Shorted Signal Circuit
2  Oxygen Sensor (Rear) Open/Shorted Signal Circuit
3  MAP Sensor MAP Sensor Electrical Problem
4  Crank Angle Sensor Sensor Circuit Problem
5  MAP Sensor MAP Sensor Mechanical Problem
6  Coolant Temp. Sensor (TW) Open/Shorted Signal Circuit
7  Throttle Angle Sensor Open/Shorted Signal Circuit
8  TDC Position Sensor Problem in TDC Sensor Circuit
9  No. 1 Cyl. Position Problem in CYL Sensor Circuit
10  Intake Air Temperature Open/Shorted Signal Circuit
12  EGR System (Calif. A/T & Hi. Alt.) No EGR Action
13  Atmospheric Pressure Open/Shorted Signal Circuit
14  Elec. Air Control Valve (EACV) EACV Circuit Problem
15  Ignition Output Signal Open/Shorted Signal Circuit
17  Vehicle Speed Sensor (VSS) No VSS Signal
18  Ign. Timing Adjustment Open/Shorted Signal Circuit
30  A/T FI Signal A Open/Shorted Signal Circuit
31  A/T FI Signal B Open/Shorted Signal Circuit
(1) If codes other than the above are indicated, repeat self- diagnosis. If code(s) reappear, substitute a known good ECU and recheck codes. If code(s) clear, replace ECU.