HOW TO: Read Check Engine Light

[infamouz]

When the computer (ECU) in your car detects a problem with how the car is running it reports it by lighting up the yellow engine light on your dash. Any Joe Schmoe can actually check what the ECU is complaining about as long as they know how.


Service Connector:
In order to get the code you'll need to find the service connector. On the 5th Gens it's on the right hand side of the centre console underneath a carpeted panel that just pops right out. The connector looks like a telephone connector and is plugged into a blue plastic piece that just serves as a holder. Unplug it and you'll see that it has two sockets in it that lead to two wires.


Getting the Code:
You'll need a small piece of wire for this. Make sure the car is off. Just connect the two ports in the service connector together with the wire. After you've shorted the service connector, turn the key in the ignition to the on position (you don't actually need to start the car) and the yellow engine light will flash at you. There will be a series of long flashes, short flashes, and then it will repeat itself. Count the number of long flashes and short flashes and this will give you the MIL code. 2 long flashes and 3 short flashes is code 23. Once you've found the code, turn the key back to off and remove the wire from the service connector. You can look up the code in the following table.

MIL Codes:

Codes	Detection Item	Probable Cause
3	Manifold Absolute Pressure Signal High/Low Signal	Open or short in MAP sensor circuit MAP sensor ECM
10	Intake Air Temperature Circuit Range/Performance Problem	Open or short in IAT sensor IAT sensor ECM
86	Engine Coolant Temperature Circuit Range/Performance Problem	ECT Sensor Cooling System
6	Engine Coolant Temperature Circuit High/Low Signal	Open or short in ECT sensor ECT sensor ECM
7	Throttle Position Circuit High/Low Signal	Open or short in TP sensor TP sensor ECM
1	Primary Heated Oxygen Circuit High/Low Signal	Open or short in Primary HO2S sensor Primary HO2S sensor ECM
61	Primary Heated Oxygen Circuit Slow response	Primary HO2S sensor ECM
41	Primary Heated Oxygen Circuit Circuit Malfunction	Open or short in Primary HO2S sensor heater circuit ECM
63	Secondary Heated Oxygen Circuit High/Low Signal Slow response	Open or short in Secondary HO2S sensor Secondary HO2S sensor Exhaust System ECM
65	Secondary Heated Oxygen Circuit Circuit Malfunction	Open or short in Primary HO2S sensor heater circuit ECM
45	System too Rich/Lean	Fuel Supply System Primary HO2S sensor Contaminated Fuel Valve Clearance Exhaust Leakage
71,72,73,74	Misfire Detected Cylinder 1 Cylinder 2 Cylinder 3 Cylinder 4	Ignition System Fuel Supply System EGR System IAC Valve Contaminated Fuel Lack of Fuel Valve Clearance Fuel Injector Circuit Low Compression
23	Knock Sensor Circuit Malfunction	Open or short in Knock Sensor (KS) circuit Knock Sensor (KS) ECM
4	Crankshaft Position Sensor Circuit Malfunction / Range / Performance	Crankshaft Position Sensor Crankshaft Position Sensor circuit ECM Timing Belt skipped teeth
80	Exhaust Gas Recirculation Insufficient flow detected	EGR Valve EGR Line/list]
67	Catalyst System Efficiency Below Threshold	Three way Catalytic Converter Secondary HO2S sensor
92	Evaporative Emission Control System Insufficient Purge Flow Purge Flow Switch Malfunction	EVAP Purge Control Solenoid Valve EVAP Purge Control Solenoid Valve Circuit EVAP Purge Flow Switch EVAP Purge Flow Switch Circuit Throttle Body (Purge Port) Tubing Vacuum connections ECM
91	Fuel Tank Pressure Sensor High/Low Input	Open or short in Fuel Tank Pressure Sensor Circuit Fuel Tank Pressure Sensor ECM
17	Vehicle Speed Circuit Malfunction	Vehicle Speed Sensor Vehicle Speed Sensor Circuit
14	Idle Control System Malfunction	IAC Valve Fast Idle Thermo Valve Throttle Body
70	Automatic Transaxle	Automatic Transmission/list]
13	Barometric Pressure Circuit Range/Performance Problem	ECM (Baro Sensor)
5	Manifold Absolute Pressure Lower/Higher than Expected	MAP Sensor
22	VTEC System Malfunction	VTEC Solenoid Valve Open or Short in VTEC Solenoid Valve circuit VTEC Pressure Switch Open or Short in VTEC Pressure Switch Circuit ECM
20	Electrical Load Detector Circuit Low/High Input	Electrical Load Detector Electrical Load Detector Circuit ECM
8	Crankshaft Position / Top Dead Center Sensor Connector Disconnection Intermittent Interruption Sensor No Signal	CKP/TDP Sensor TDC Sensor Circuit ECM
9	Cylinder Position Sensor Intermittent Interruption No Signal	CYP Sensor CYP Sensor Circuit ECM
90	Evaporative Emission Control System Leak Detected (Fuel Tank System) Leak Detected (EVAP Control Canister System)	Fuel Fill Cap Vacuum connection Fuel tank Fuel tank pressure sensor EVAP bypass solenoid valve EVAP two way valve EVAP control canister vent shut valve EVAP control canister EVAP purge control solenoid valve
92	Evaporative Emission Purge Flow Switch Malfunction	EVAP Purge flow switch EVAP Purge flow switch circuit Vacuum connections ECM
12	EGR Valve Lift Sensor Lift Insufficient Detected High Voltage	EGR Valve (with lift sensor) EGR valve lift sensor circuit EGR control solenoid valve EGR control solenoid valve circuit EGR line ECM
14	Idle Air Control Valve Circuit Failure	IAC Valve IAC Valve circuit ECM
30	SEAF/SEFA Signal Line Failure	Open or short in SEAF/SEFA circuit