Does anyone know how to diagnose the CEL on a 1991 Civic STD hatchback? Thanks in advance.

 

Turn the ignition to the "On" position, pull up the carpet on the passenger side floorpan. May have to remove the cover over the ECU. Count the LED blinks, then look up the code or tell us what it is and we can decipher it.

 

The light on the ECU blinks once every 4 seconds. Is that code 10? Can anyone tell me what code my ECU is throwing? Thanks.

 

CEL Codes!!! Refer to the bottom for more info.

1 Integra Oxygen Sensor "A" (Primary) defective circuit or unplugged / defective sensor

2 Oxygen Sensor "B" defective circuit or unplugged / defective sensor

3 MAP Sensor (Manifold Absolute Pressure) defective circuit or unplugged / defective sensor

4 CKP Sensor (Crankshaft Position Sensor) defective circuit or unplugged / defective sensor

5 MAP Sensor (Manifold Absolute Pressure) mechanical problem / disconnected piping

6 ECT Sensor (Engine Coolant Temperature) defective circuit or unplugged / defective sensor

7 TP Sensor (Throttle Position) defective circuit or unplugged / defective sensor

8 TDC Sensor (Top Dead Center) defective circuit or unplugged / defective sensor

9 CYP Sensor (Cylinder) defective circuit or unplugged / defective sensor

10 IAT Sensor (Intake Air Temperature) defective circuit or unplugged / defective sensor

12 EGR Lift Sensor (Exhaust Gas Recirculation) defective circuit or unplugged / defective sensor

13 BARO Sensor (Atmospheric Pressure) defective circuit or unplugged / defective sensor

14 IAC Valve (Idle Air Control) defective circuit or unplugged / defective sensor

15 Ignition Output Signal missing or defective ignition output signal

16 Fuel Injector System defective circuit or unplugged / defective fuel injector

17 VSS (Vehicle Speed Sensor) defective circuit or unplugged / defective sensor

19 Automatic Transmission Lock Up Control Solenoid Valve defective circuit or unplugged / defective solenoid valve

20 Electrical Load Detector defective circuit or unplugged / defective sensor

21 VTEC Solenoid Valve defective circuit or unplugged / defective solenoid valve

22 VTEC Oil Pressure Switch defective circuit or unplugged / defective oil pressure switch

23 KS (Knock Sensor) defective circuit or unplugged / defective sensor

30 Automatic Transmission Signal: "A" / SEAF / SEFA / TMA or TMB defective circuit or unplugged / defective sensor

31 Automatic Transmission Signal "B" defective circuit or unplugged / defective sensor

41 Primary Oxygen Sensor - Heater circuit malfunction

43 Fuel Supply System defective or malfunctioning fuel supply
system

45 System Too Lean or Too Rich malfunction in the fuel monitoring systems

48 LAF Sensor (Lean Air Fuel) defective circuit or unplugged / defective sensor

54 CKF Sensor (Crankshaft Speed Fluctuation) defective circuit or unplugged / defective sensor

61 Oxygen Sensor, Heated - Sensor 1 (Primary) high voltage, low voltage, or slow response

63 Oxygen Sensor, Heated - Sensor 2 (Secondary) high voltage, low voltage, or slow response

65 Oxygen Sensor Heater (Secondary) malfunctioning or defective oxygen sensor heater

67 Catalyst system Efficiency Below Threshold malfunctioning or defective catalyst system

70 Automatic Transmission malfunction with the automatic transmission controls

71 Cylinder 1 Misfire or a Random Misfire a condition is present that is creating a cylinder misfire

72 Cylinder 2 Misfire or a Random Misfire a condition is present that is creating a cylinder misfire

73 Cylinder 3 Misfire or a Random Misfire a condition is present that is creating a cylinder misfire

74 Cylinder 4 Misfire or a Random Misfire a condition is present that is creating a cylinder misfire

80 Exhaust Gas Recirculation insufficient flow detected

86 ECT Sensor (Engine Coolant Temperature) circuit range /
performance problem

90 Evaporative Emission Control System leak detected in the fuel tank area

91 Fuel Tank Pressure Sensor low input

92 Evaporative Emission Control System insufficient purge flow

You will notice that there will be LONG flashes and SHORT flashes. All of the ECU trouble codes are two-digits. LONG flashes determine the TENS digit by the number of times it flashes, and SHORT flashes determine the ONES digit by the number of times it flashes.

ie. LONG-LONG-LONG-SHORT-SHORT-SHORT-SHORT-PAUSE

is the trouble code: 34

3 LONG flashes followed by 4 short flashes, then a long pause. If that is the only code the ECU is throwing, then the code will simply repeat until you remove the key. If, however there are more than one ECU error code, then you will see a different series of flashes followed by the long pause. Once all the ECU codes have been displayed, they will continuously cycle until you remove the key.

ie. LONG-LONG-SHORT-PAUSE-LONG-LONG-LONG-LONG-SHORT-SHORT-SHORT-PAUSE

is the trouble code: 21 and 43

http://www.c-speedracing.com/faq/05.php <----good link.