This facility is built into the PCM, and is designed to alert the driver to a system component fault which may result in a higher than normal emissions of harmful exhaust/fuel vapour gases and speed up the engine management troubleshooting procedure. Should an engine management component fail, the incorrect (or implausible) signal is recognised by the PCM, which stores a Diagnostic Trouble Code (DTC), and where appropriate, illuminates the Malfunction Indicator Light (MIL)/Check Engine Light (CEL) in the instrument cluster.
In order to retrieve any stored DTC's, either a fault code reader must be connected to the vehicle's data link connector (located above the Service Check Connector), or read from the MIL in the instrument cluster.
Reading the Check Engine Light
The service check connector (2-pin) is located under the dashboard, above the passenger side kick panel. By default it is inserted into a green rubber housing. for 92-95 models it is gray, 96-00 models its blue. The codes can be read by bridging the two pins in the service connector and reading the MIL on the instrument cluster (all models). Vehicles 2000 onwards are fitted with a 16-pin diagnostic behind the centre console on the passenger side. A fault code reader is required to retrieve or clear codes via this connector.
To view any DTC's stored in the PCM memory (without a code reader), fit a bridging wire into service check connector then turn the ignition switch to the ON position. If any codes are present, they will blink a sequence in the MIL to indicate a system or component failure.
The MIL will blink longer to represent the first digit and then will blink short for the second (for example 1 long and 6 short would be code 16). If the system has more than one problem, the codes will be displayed in sequence, there will be a pause, then the codes will repeat.
When the PCM sets DTC, the MIL will come on and trouble code will be stored in the memory. The trouble code will stay in the PCM until voltage to the PCM is interrupted. To clear the memory, remove the BACK-UP fuse from the fuse relay box located in the engine compartment for at least ten seconds. NOTE - This will also clear any radio presets/codes.
Common Diagnostic Trouble Codes
1 O2A - Oxygen sensor #1 2 O2B - Oxygen sensor #2 3 MAP - manifold absolute pressure sensor 4 CKP - crank position sensor 5 MAP - manifold absolute pressure sensor 6 ECT - water temperature sensor 7 TPS - throttle position sensor 8 TDC - top dead centre sensor 9 CYP - cylinder sensor 10 IAT - intake air temperature sensor 12 EGR - exhaust gas recirculation lift valve 13 BARO - atmospheric pressure sensor 14 IAC (EACV) - idle air control valve 15 Ignition output signal 16 Fuel injectors 17 VSS - speed sensor 19 Automatic transmission lockup control valve 20 Electrical load detector 21 VTEC spool solenoid valve 22 VTEC pressure valve 23 Knock sensor 30 Automatic transmission A signal 31 Automatic transmission B signal 36 traction control found on JDM ecu's 41 Primary oxygen sensor heater 43 Fuel supply system 45 Fuel system too rich or lean 48 LAF - lean air fuel sensor 54 CKF - crank fluctuation sensor 58 TDC sensor #2 61 Primary oxygen sensor 63 Secondary oxygen sensor circuit 65 Secondary oxygen sensor heater wire (black wires) 67 Cat Converter 71 random misfire cylinder 1 72 random misfire cylinder 2 73 random misfire cylinder 3 74 random misfire cylinder 4 80 EGR Valve/Line 86 ECT sensor - Cooling System 91 Fuel Tank pressure sensor 92 EVAP Solenoid/Valve/Vacuum Lines