Technical Information ECU Problem Codes

What are ECU problem codes?

ECU problems codes are diagnostic outputs from the ECU, used to indicate in what area a problem lies. Usually the check engine warning light (on the dash) will come on for a serious problem, but will not necessarily come on for a minor problem. The ECU will remember problem codes with the ignition off; the only way to clear the codes is to disconnect the battery or remove the hazard fuse for half a minute or so.

How to read ECU codes.

To read the codes, turn the ignition on and look at the LED inside the ECU. The LED is visible through a small plastic window in the top of the ECU. The ECU can signal simultaneous problems by blinking separate codes, one after the other. Problem codes 1 - 9 are indicated by 1 - 9 flashes, problem codes over 9 use one long flash as ten short flashes.


OBDI and later ECUs
Find the  diagnostic connector, which is a two wire blue connector found near the passengers feet, or in the centre console.
Short out the diagnostic connector with a piece of wire.  The check engine light on the dash will flash the problem codes.

Code Meaning
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
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
65 Secondary oxygen sensor heater