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Manually Reading ECU Codes


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On Classic shape only (not Newage) faults can be displayed as pulses of the Check Engine Light. If the Check Engine Light goes out there is no fault. In order to perform diagnostic (and ECU resets) you will need to connect some wires together under your steering column.


Note, the following procedure only works for Classic shape Impreza’s, not for Newage. Make sure your ignition is OFF Connect the Black ‘Read Memory’ connectors together as illustrated below.




When the above are connected you are in diagnostics mode. Turn your ignition ON and ‘read’ the ECU code(s) being reported according to the following instructions. Note, you may here relays clicking and your fan starting and stopping - this is normal when in diagnostics mode.

In Diagnostic Mode – No Fault is indicated by the Check Engine Light continuously & evenly flashing on/off (this is also used to indicate the successful completion of an ECU Reset).

Figure 2 - Check Engine Light Pulse Width

The long pulses (1.3 Seconds) indicate Tens and the short pulses (0.2 Seconds) indicate ones. Pulses are separated by Short Pauses (0.2 Seconds), multiple codes are separated by a Long Pause (1.8 Seconds).

The simplest way for an inexperienced mechanic to retrieve codes is to write the codes down in a sort of Morse Code (dots and dashes), and start a new line when you get a 1.8 Second pause (for NEW code), and then add the actual numbers up after code retrieval is completed.

(See Example Below)


1.3 second pulse (10) 
0.2 second pause 
1.3 second pulse (10….for a total of 20) 
0.2 second pause 
0.2 second pulse (1…..for a total of 21) 
0.2 second pause 
0.2 second pulse (1…..for a total of 22) 
0.2 second pause 
0.2 second pulse (1…..for a total of 23) 
(Code 23 — MAF Sensor)


1.3 second pulse (10) 
0.2 second pause 
1.3 second pulse (10….for a total of 20) 
0.2 second pause 
0.2 second pulse (1…..for a total of 21) 
0.2 second pause 
0.2 second pulse (1…..for a total of 22) 
0.2 second pause 
0.2 second pulse (1…..for a total of 23) 
1.8 second pause (this means NEW code)

1.3 second pulse (10) 
0.2 second pause 
0.2 second pulse (1…..for a total of 11) 
0.2 second pause 
.2 second pulse (1…..for a total of 12) 
(Codes 23 and 12, MAF Sensor and Starter Circuit)




How to clear them!


  1. Ensure engine is at normal operating temperature, turn engine off
  2. Locate the two ECU connectors, located under the steering column and consist of a black plastic male and female connector, and a green male female connector
  3. With the ignition OFF connect black to black and green to green.
  4. Turn on ignition, do not start the engine, depress the accelerator pedal to full throttle, then return it to the half-throttle position and hold for a few seconds, and then release
  5. Engine Check lamp turns on
  6. Start engine and then drive for at least one minute, keeping road speed above 10mph.
  7. ECU is now re-set.
  8. At this point the check engine light should start to flash the all clear signal (steady 1/2 second interval flashes). If the check engine light does not flash, or indicates some other sequence, there is a fault present in the system, and should be professionally checked for necessary repairs.
  9. Stop the car and turn off the engine.
  10. Disconnect the black and green connectors.
  11. Job complete
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  • 4 weeks later...

1 Engine Speed Signal Circuit

11 Crankshaft Position Sensor

12 Starter Signal

13 Camshaft Position Sensor

14 Fuel Injector No. 1 (Legacy, Impreza, Justy, SVX)

15 Fuel Injector No. 2 (Legacy, Impreza, Justy, SVX)

16 Fuel Injector No. 3 (Legacy, Impreza, Justy, SVX)

17 Fuel Injector No. 4 (Legacy, Impreza, SVX)

18 Fuel Injector No. 5 (SVX)

19 Fuel Injector No. 6 (SVX)

21 Engine Coolant Temperature Sensor

22 Knock Sensor

23 Mass Air Flow Sensor Circuit

24 Idle Control System Malfunction

24 ISC Valve (Stick)

24 Open/Short in ISC Valve Circuit

26 Intake Air Temperature Sensor

27 ATF Temperature Sensor Circuit

28 Knock Sensor #2

29 Crankshaft Position Sensor 2

31 Throttle Position Sensor Circuit

32 A/F Sensor #1 System

32 A/F Sensor #2 System

32 Oxygen Sensor

33 Vehicle Speed Sensor

35 CPC System

36 Turbine Speed Signal

37 Rear O2 Sensor Circuit / A/F Sensor Circuit Malfunction

38 Torque Control Signal #1

38 Torque Control Signal #2

38 Torque Control Signal System

38 Torque Permission Signal

39 Traction Control System

41 Air/Fuel Adaptive Control

42 Idle Switch

43 Accelerator Pedal Switch

44 Turbocharging Pressure Control Signal

45 Pressure Sensor

46 Neutral or Parking Switch or Circuit

47 Fuel Injector

48 Lean Burn System

49 CO Resistor

51 Neutral Position Switch

52 Parking Brake Switch (Exc. Justy)

53 Antenna

53 Anti-Quick Operation Mode

53 Communication Error (Time Over)

53 EGI Control Module EEPROM

53 IMM Circuit Failure (Except Antenna Circuit)

53 IMM Control Module EEPROM

53 Key Communication Failure

53 Reference Code Incompatibility

53 Use of Unregistered Key

54 Air Intake System

55 EGR Valve Lift Sensor

56 EGR System

57 Canister Control System

58 Air Control System

61 Air Suction Control Solenoid Valve

62 Exhaust Manifold Valve Negative Pressure Control Solenoid

64 Relief Valve Control Solenoid Valve 1

64 Relief Valve Control Solenoid Valve 2

65 Differential Pressure Sensor

66 Twin Turbocharger System(H)

66 Twin Turbocharger System(S)

66 Twin Turbocharger System(T)

66 Two Stage Twin Turbocharger System

67 Exhaust Manifold Valve Positive Pressure Control Solenoid

68 Turbocharging Pressure Control Output Signal #2

71 Shift Solenoid Valve

72 Shift Solenoid #2 Circuit

73 Low Clutch Timing Solenoid Circuit

74 Brake Clutch Timing Solenoid Circuit Malfunction

75 Line Pressure Duty Solenoid Circuit

76 Brake Clutch Pressure Duty Solenoid Circuit Malfunction

77 Lock-Up Duty Solenoid Circuit

78 Tiptronic Solenoid System

79 Transfer Clutch Duty Solenoid Circuit

81 Torque Up Control Valve

85 Charger System Circuit Malfunction

86 CAN (Communication System)

87 Variable Induction Solenoid Valve Circuit Malfunction

88 Fuel Pump Circuit Malfunction

89 VVT Systems (L)

89 VVT Systems ®

91 TCS Relief Valve

92 Electrical Generation Control Signal Circuit Malfunction

93 Vehicle Speed Sensor #1 Circuit

94 Lateral G Sensor Signal Circuit Malfunction

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  • 3 months later...

Not sure I seem to hear mixed reviews on that some say it works others have said it didn't but the way described above is the true factory built way to do it. And it really isn't too hard they should be just tucked away. But I would say you can try the Battery if that feels better for you to try :)  

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  • 4 months later...
  • 3 months later...

So to clarify a few things.If I plug the 2 black wires together and the check light flashes continuously there is no fault.If the black wires are connect and the fan kicks in and the relays click there is a fault? when I plugged the green and black wires together the relays and the fans started operating :lol: .But if I just plugged the black one together the check light just flashed constant with no change. :wacko:

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Sorry for the late reply here goes. The issues I had with my scoobie. The lad I bought it off had put new cambelt on didn't time it so was all out. Oil leak well the oil pump was in bit's more or less. So since I bought the car in April she's had a new sstarter motor cambelt kit with ttensioners water pump and oil pump. Getting clutch done 12 September. And mot .. then after that oil and plugs.. so she is getting there slowly

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Connect black to black only to read fault codes, then green as well for function test mode & resetting ecu.

What do you mean by a function test.When I plug green and black wires the fan kicks in but if its just black wires there is no fan starting or clicking of the wires.A little confusing.Im not a sparky lol

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if its the black wires that just need going together and the check light flashes constant then I have no fault yet my car hiccups every now and again like a misfire.And ive even changed my pump back to the original pump just to test :wacko: so im stumped

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  • 5 months later...

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