John, I cut this out of an American Civic site for you:-
If your CEL has illuminated, it is more helpful to know WHY it has lit up instead of just guessing at the problem... How do you find out what the error is? Well you will need a short peice of wire or a paperclip.
On the passenger side of your car, under the dash beneath the glove box, you will find a green cover above the kickpanel that houses a blue connector that has two wires.
That you need to do is turn the ignition off, and using the piece of wire or paperclip, jump the blue connector so that you connect the two wires together. Basically stick one end of the paperclip or peice of wire into one prong on the connector and stick the other end of the paperclip or wire into the other prong.
Once you have done this, turn the key to the IGN position and watch your CEL light. It will illuminate in a series of flashes.
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
Once you have determined the codes, you can simply remove the paperclip or wire from the connector and replace it back in the green housing.
So now you have the codes, what good are the numbers? What do they mean? Refer to the TROUBLE CODES section.
CODE VEHICLE DEFINITION
1 86-98 Civic
97-98 CRV
85-98 Prelude
94+ Integra Oxygen Sensor "A" (Primary) defective circuit or unplugged / defective sensor
2 86-87 Civic
Oxygen Sensor "B" defective circuit or unplugged / defective sensor
3 86-98 Civic
97-98 CRV
85-98 Prelude
94+ Integra MAP Sensor (Manifold Absolute Pressure) defective circuit or unplugged / defective sensor
4 88-98 Civic
97-98 CRV
85-98 Prelude
94+ Integra CKP Sensor (Crankshaft Position Sensor) defective circuit or unplugged / defective sensor
5 86-98 Civic*
97-98 CRV
85-98 Prelude
94+ Integra MAP Sensor (Manifold Absolute Pressure) mechanical problem / disconnected piping
* not 94-95
6 86-98 Civic
97-98 CRV
85-98 Prelude
94+ Integra ECT Sensor (Engine Coolant Temperature) defective circuit or unplugged / defective sensor
7 86-98 Civic
97-98 CRV
85-98 Prelude
94+ Integra TP Sensor (Throttle Position) defective circuit or unplugged / defective sensor
8 86-98 Civic
97-98 CRV
85-98 Prelude
94+ Integra TDC Sensor (Top Dead Center) defective circuit or unplugged / defective sensor
9 86-98 Civic
97-98 CRV
85-98 Prelude
94+ Integra CYP Sensor (Cylinder) defective circuit or unplugged / defective sensor
* invalid code for throttle body injection Hondas
** invalid code for V6 engines
10 86-98 Civic
97-98 CRV
85-98 Prelude
94+ Integra IAT Sensor (Intake Air Temperature) defective circuit or unplugged / defective sensor
12 86-98 Civic
85-98 Prelude
94+ Integra EGR Lift Sensor (Exhaust Gas Recirculation) defective circuit or unplugged / defective sensor
* invalid code for non-equipped EGR valve vehicles
13 86-98 Civic
97-98 CRV
85-98 Prelude
94+ Integra BARO Sensor (Atmospheric Pressure) defective circuit or unplugged / defective sensor
14 88-98 Civic
97-98 CRV
88-98 Prelude
94+ Integra IAC Valve (Idle Air Control) defective circuit or unplugged / defective sensor
15 88-95 Civic
88-95 Prelude
94+ Integra Ignition Output Signal missing or defective ignition output signal
16 88-95 Civic
88-85 Prelude
94+ Integra Fuel Injector System defective circuit or unplugged / defective fuel injector
17 88-98 Civic
97-98 CRV
88-98 Prelude
94+ Integra VSS (Vehicle Speed Sensor) defective circuit or unplugged / defective sensor
19 88-95 Civic
94+ Integra Automatic Transmission Lock Up Control Solenoid Valve defective circuit or unplugged / defective solenoid valve
20 88-98 Civic
97-98 CRV
92-98 Prelude
94+ Integra Electrical Load Detector defective circuit or unplugged / defective sensor
21 92-95 Civic
93-95 Prelude
94+ Integra VTEC Solenoid Valve defective circuit or unplugged / defective solenoid valve
* invalid code for non-VTEC engine
** invalid for V6 engine
22 92-98 Civic
93-98 Prelude
94+ Integra VTEC Oil Pressure Switch defective circuit or unplugged / defective oil pressure switch
* invalid code for non-VTEC engine
23 96-98 Civic
92-98 Prelude
94+ Integra KS (Knock Sensor) defective circuit or unplugged / defective sensor
* invalid code for V6 engine
30 92-98 Prelude
94+ Integra Automatic Transmission Signal: "A" / SEAF / SEFA / TMA or TMB defective circuit or unplugged / defective sensor
* invalid code for 1996
31 92-95 Prelude Automatic Transmission Signal "B" defective circuit or unplugged / defective sensor
41 92-98 Civic
97-98 CRV
90-98 Prelude
94+ Integra Primary Oxygen Sensor - Heater circuit malfunction
43 92-95 Civic
90-95 Prelude
94+ Integra Fuel Supply System defective or malfunctioning fuel supply system
45 96-98 Civic
97-98 CRV
96-98 Prelude
94+ Integra System Too Lean or Too Rich malfunction in the fuel monitoring systems
48 92-98 Civic
94+ Integra LAF Sensor (Lean Air Fuel) defective circuit or unplugged / defective sensor
54 96-98 Civic
97-98 CRV
94+ Integra CKF Sensor (Crankshaft Speed Fluctuation) defective circuit or unplugged / defective sensor
61 96-98 Civic
97-98 CRV
96-98 Prelude
94+ Integra Oxygen Sensor, Heated - Sensor 1 (Primary) high voltage, low voltage, or slow response
63 96-98 Civic
97-98 CRV
96-98 Prelude
94+ Integra Oxygen Sensor, Heated - Sensor 2 (Secondary) high voltage, low voltage, or slow response
65 96-98 Civic
97-98 CRV96-98 Prelude
94+ Integra Oxygen Sensor Heater (Secondary) malfunctioning or defective oxygen sensor heater
67 96-98 Civic
97-98 CRV
96-98 Prelude
94+ Integra Catalyst system Efficiency Below Threshold malfunctioning or defective catalyst system
70 96-98 Civic
97-98 CRV
96-98 Prelude
94+ Integra Automatic Transmission malfunction with the automatic transmission controls
71 96-98 Civic
97-98 CRV
96-98 Prelude
94+ Integra Cylinder 1 Misfire or a Random Misfire a condition is present that is creating a cylinder misfire
72 96-98 Civic
97-98 CRV
96-98 Prelude
94+ Integra Cylinder 2 Misfire or a Random Misfire a condition is present that is creating a cylinder misfire
73 96-98 Civic
97-98 CRV
96-98 Prelude
94+ Integra Cylinder 3 Misfire or a Random Misfire a condition is present that is creating a cylinder misfire
74 96-98 Civic
97-98 CRV
96-98 Prelude
94+ Integra Cylinder 4 Misfire or a Random Misfire a condition is present that is creating a cylinder misfire
80 96-98 Civic
96-98 Prelude
94+ Integra Exhaust Gas Recirculation insufficient flow detected
86 96-98 Civic
97-98 CRV
96-98 Prelude
94+ Integra ECT Sensor (Engine Coolant Temperature) circuit range / performance problem
90 96-98 Civic
97-98 Prelude
94+ Integra Evaporative Emission Control System leak detected in the fuel tank area
91 96-98 Civic
97-98 Prelude
94+ Integra Fuel Tank Pressure Sensor low input
92 96-98 Civic
97-98 CRV
96-98 Prelude
94+ Integra Evaporative Emission Control System insufficient purge flow
Here's the link to make it easier.
http://www.c-speedracing.com/faq/06.php
Hope this helps,
regards Rob.