Tech

How to display and interpret the Check Engine Light 'blink codes'.

It's not hard but the text below is full of TLA's (Three Letter Acromyms) so pay attention.

The CEL (Check Engine Light) may illuminate indicating a possible problem with the car's engine or emissions system. Normally you would take the car to the dealer where they connect a 'scan tool' to communicate with the ECM (Engine Control Module) and display the DTC (Diagnostic Trouble Code).

But some of those DTC's can be read without a scan tool by putting the ECM into a diagnostic mode where it blinks the CEL with a series of long (1 - 2 seconds) and short (1/2 second) blinks. Some DTC's don't have a corresponding blink code, or have a blink code that is not as specific as the actual DTC. But they are still useful, especially if you want to do some troubleshooting without paying the dealer $85 to read the DTC.

Sample movie of a real blink code in action here

This is a 30 second Windows Media file (1MB) showing the CEL blinking 6 - 3. You will see 6 long blinks, pause, 3 short blinks, long pause, then the process repeats. Try not to be confused by the blinking EPS and ABS lights.

Here's how to do this on your S2000:

(all photos are click-able for larger versions)

Here's a photo of where you'll find the DLC (Diagnostic Link Connector), otherwise known as the OBDII connector (On Board Diagnostics). It's just under the dash on the passenger side of the tunnel. This is where the dealer plugs in the Scan Tool and where Emissions Testing stations connect. Note: on years 02 and newer, the DLC is on the driver's side above the tunnel and sort of behind the radio. You can see it from under the driver's dash if you look towards the tunnel.
Here's a view of the DLC as seen from open side of the connector (looking up from the floor). Pin 1 is the pin closest to the tunnel and towards the front of the car, and has a BROWN wire connected to it, called the SCS wire (Service Check System). Make sure you get the right pin 1. The pin in the other corner is +12v so don't short it to ground!!!!
Close-up of DLC showing pin 1. If you ground the brown wire in pin 1, the ECM will cause the CEL to blink if there is a valid blink code for the stored DTC. You can bend a paper clip to fit into the sockets for pin 1 and one of the ground wires, or if you want to wire a permanent switch, use the wire at the ECM (see below). While you could wire directly to the DLC SCS wire, there is very little slack in the wires, which is why I didn't use it.
The SCS wire can also be found on the ECM, which is behind the driver's foot well cover. Here's a photo of the ECM. The red rectangle indicates the connector where you will find the BROWN SCS wire. Don't worry if your car doesn't have as many wires as mine. I think I've got the lock on that record.
Here's a blowup of the red rectangle area showing the BROWN Service Check wire. It's pretty easy to get to. If you're going to connect to it here, don't cut the wire, use a T-tap connector. That's what I did, and then wired it to a permanent switch so I can easily put the ECM into diagnostic mode whenever I want.
I installed two small rocker switches in the blank switch cover behind the wiper lever. MY '02 cars and newer may have a Rear Defroster switch here. One of these switches grounds the SCS wire so I can read the blink codes. The other one activates the ejection seat. Do you feel lucky?

The Honda Shop manual says to jump out the SCS wire (ground the BROWN wire in pin 1), then turn the ignition ON to read the blink codes. In actuality you can ground the SCS wire anytime, even with the engine running. I have successfully read the codes while driving, but it's not recommended. Using this method the first blink code is sometimes 'bogus', I assume because I've caught the ECM while it was busy doing something else and it started blinking in the middle of the pattern. No big deal, the codes will repeat forever as long as you have the SCS wire grounded.

In the chart below I have listed all the blink codes I have found from various sources. You may have more than one DTC logged, so you may get multiple blink codes. Watch the pattern several times to make sure you get them all.

DTC	Blink Code Long-Short	Temporary DTC	Detection Item
	0 - 0		ENGINE CONTROL MODULE (ECM)
P0131	0 - 1	---------------	Primary Heated Oxygen Sensor Circuit Low Voltage (Sensor 1)
P0132	0 - 1	---------------	Primary Heated Oxygen Sensor Circuit High Voltage (Sensor 1)
P0107	0 - 3	---------------	Manifold Absolute Pressure Circuit Low Input
P0108	0 - 3	---------------	Manifold Absolute pressure Circuit High Input
P0335	0 - 4	---------------	Crankshaft Position (CKP) Sensor Circuit Malfunction
P0336	0 - 4	---------------	Crankshaft Position (CKP) Sensor Range/Performance
P0117	0 - 6	---------------	Engine Coolant Temperature Circuit Low Input
P0118	0 - 6	---------------	Engine Coolant Temperature Circuit High Input
P0122	0 - 7	---------------	Throttle Position Circuit Low Input
P0123	0 - 7	---------------	Throttle Position Circuit High Input
	0 - 8		TOP DEAD CENTRE POSITION 1 (TDC1) SENSOR
P0112	1 - 0	---------------	Intake Air Temperature Circuit Low Input
P0113	1 - 0	---------------	Intake Air Temperature Circuit High Input
	1 - 3		BAROMETRIC PRESSURE (BARO) SENSOR
	1 - 4		IDLE AIR CONTROL (IAC) VALVE
	1 - 7		VEHICLE SPEED SENSOR (VSS)
	2 - 0		ELECTRICAL LOAD DETECTOR (ELD)
	2 - 2		VTEC SOLENOID VALVE
P0325	2 - 3	---------------	Knock Sensor (KS) Circuit malfunction
P0135	4 - 1	---------------	Primary Heated Oxygen Sensor Heater Circuit Malfunction (Sensor 1)
P0171	4 - 5	P0170	Fuel System Too Lean
P0172	4 - 5	P0170	Fuel System Too Rich
	5 - 8		TOP DEAD CENTRE POSITION 2 (TDC2) SENSOR
	6 - 0		AIR PUMP
P0133	6 - 1	P0133	Primary Heated Oxygen Sensor Slow Response (Sensor 1)
P0137	6 - 3	P0136	Secondary Heated Oxygen Sensor Circuit Low Voltage (Sensor 2)
P0138	6 - 3	P0136	Secondary Heated Oxygen Sensor Circuit High Voltage (Sensor 2)
P0139	6 - 3	P0136	Secondary Heated Oxygen Sensor Slow Response (Sensor 2)
P0141	6 - 5	---------------	Secondary Heated Oxygen Sensor Heater Circuit Malfunction (Sensor 2)
P0420	6 - 7	---------------	Catalyst System Efficiency Below Threshold
P0301	7 - 1	P1399	Cylinder 1 Misfire Detected
P0302	7 - 2	P1399	Cylinder 2 Misfire Detected
P0303	7 - 3	P1399	Cylinder 3 Misfire Detected
P0304	7 - 4	P1399	Cylinder 4 Misfire Detected
P0412	8 - 4	---------------	Air Control Valve Circuit Low Voltage
P0443	9 - 2	---------------	Evaporative Emission (EVAP) Purge Control Solenoid Valve Circuit Malfunction
P0300 with P0301 or P0302 or P0303 or P0304	7 - 1 7 - 2 7 - 3 and/or 7 - 4	P1399	Random Misfire