Electronic Control System: Testing: Notes

NOTE: Before starting testing, ensure engine is in good mechanical condition and adjusted to specifications.

On all models, an LED is located on ECU for self-diagnostic codes. LED is used to read codes set due to component failure. When the Check Engine warning light has been reported on, pull down the passenger's side carpet from under the dashboard, turn the ignition on, and observe the LED on the top of the ECU. The LED indicates a system failure code by blinking frequency. The ECU LED can indicate any number of separate or simultaneous component problems by blinking codes, one after another. See Fig 1 . See appropriate LED CODES table in this article.

NOTE: If unlisted codes are flashed by ECU LED, clear codes and recheck. If code still appears, substitute a known good ECU. If condition is rectified, replace original ECU.

On all models, System Checker Harness (07999-PD60000A ) is needed to test components. See Fig 2 . This device function as breakout boxes to access pin voltage signals while component is either in or out of circuit.

To reset ECU, remove hazard fuse in main fuse box for 10 seconds.

CIVIC LED CODES

LED Blinks	System Code
0	ECU
1	Oxygen Sensor
3	MAP Sensor
4	Crank Angle Sensor
5	MAP Sensor
6	Coolant Temperature
7	Throttle Angle Sensor
8	TDC Sensor
9	No. 1 CYL Sensor (HF & Si)
10	Intake Air Temperature
11	IMA Sensor (Without O2 & Catalyst)
12	EGR System (HF)
13	Atmospheric Pressure Sensor
14	Electronic Air Control Valve
15	Ignition Output Signal
16	Fuel Injector
17	Vehicle Speed Sensor
19	Lock-Up Solenoid Valve (Auto. Trans.)
20	Electric Load Detector

Fig 1: ECU LED Location & Blinking Frequency Examples

Fig 2: ECU Terminal I.D. & System Checker Harness Installation