Service connector and codes

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Service connector and codes:

How to get Prelude CEL codes and what they mean


  • Get a paperclip and bend it into a U shape.
  • Make sure the engine’s off and look behind the centre console near the clutch pedal for the service connector; it’s a little (normally) blue connector with 2 wires attached.
  • Insert the paperclip into the connector to short the 2 wires.
  • Now turn on the ignition but don’t start the engine, so the dash warning lights light up.
  • If the CEL light on the dash stays on permanently there are no CEL problems.
  • If it starts to flash you’ll need to make a note of how many flashes there are.
  • The CEL light will flash in a loop if there is more than 1 problem


  • Short flashes mean 1
  • Long flashes mean 10


Here is the list of codes taken from the Honda Workshop Manual

0 Engine Control Module (ECM)

1 Heated Oxygen Sensor (HO2S)

3 Manifold Absolute Pressure (MAP SENSOR)

4 Crankshaft Position (CKP SENSOR)

5 Same as above

6 Engine Coolant Temperature (ECT SENSOR)

7 Throttle Position (TP SENSOR)

8 Top Dead Centre Position (TDC SENSOR)

9 No. 1 Cylinder Position (CYP SENSOR)

10 Intake Air Temperature (IAT SENSOR)

12 Exhaust Gas Recirculation (EGR VALVE LIFT SENSOR)

13 Barometric Pressure (BARO SENSOR)

14 Idle Air Control (IAC VALVE)

15 Ignition Output Signal

16 Fuel Injector

17 Vehicle Speed Sensor (VSS)

20 Electric Load Detector (ELD)

21 Variable Valve Timing & Valve Lift Electronic Control (VTEC) Solenoid Valve

22 Variable Valve Timing & Valve Lift Electronic Control (VTEC) Pressure Switch

23 Knock Sensor (KS)

41 Heated Oxygen Sensor (HO2S) Heater

43 Fuel Supply System



obd1 check engine codes


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

36 traction control found on JDM ecu's

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

71 random misfire cylinder 1

72 random misfire cylinder 2

73 random misfire cylinder 3

74 random misfire cylinder 4

80 Exhaust Gas Recirculation insufficient flow detected

86 ECT Sensor (Engine Coolant Temperature) circuit range / performance problem

90 Evaporative Emission Control System leak detected in the fuel tank area

91 Fuel Tank Pressure Sensor low input

92 Evaporative Emission Control System insufficient purge flow