So I have a '94 4X4 Hardbody with a CEL. I found the list of codes online, but I am a bit confused. The diagnostics lights flash as follows: 1 long, 2 long, 3 short, 4 short, 5 short. Here is the list of possible codes that I found online: 1. Turn the ignition switch on, but do not start the engine. All of the lights in the dash should be on. 2. Turn the 'diagnostic mode selector' screw on the ECU fully clockwise. The check engine light will go out. Wait 5 seconds, then turn the screw fully counter clockwise. 3. The check engine light will then begin to flash the trouble code. (number of long flashes is the 1st digit, number of short flashes is the 2nd digit) 4. To clear all stored codes and turn the check engine light off, turn the screw fully clockwise. Wait 5 seconds, then turn the screw fully counter clockwise. 5. To keep the codes stored, simply turn the key off as the check engine light is flashing and the ECU will keep all stored codes and the check engine light will remain on. Nissan Flash Codes 11 Crank Angle Sensor/Camshaft Position Sensor. 12 Air Flow Meter/Mass Air Flow Sensor. 13 Engine Coolant Temperature Sensor. 14 Vehicle Speed Sensor. 21 Ignition Signal. 22 Fuel Pump. 23 Idle Switch. 24 Throttle Valve Switch. 25 Idle Speed Control Valve. 28 Cooling Fan Circuit. 31 ECM. 32 EGR Function. 33 Heated Oxygen Sensor. 34 Knock Sensor. 35 Exhaust Gas Temperature Sensor. 36 EGR Control-Back Pressure Transducer. 37 Knock Sensor. 38 Right hand bank Closed Loop (B2). 41 Intake Air Temperature Sensor. 42 Fuel Temperature Sensor. 43 Throttle Position Sensor. 45 Injector Leak. 47 Crankshaft Position Sensor. 51 Injector Circuit. 53 Oxygen Sensor. 54 A/T Control. 55 No Malfunction. 63 No. 6 Cylinder Misfire. 64 No. 5 Cylinder Misfire. 65 No. 4 Cylinder Misfire. 66 No. 3 Cylinder Misfire. 67 No. 2 Cylinder Misfire. 68 No. 1 Cylinder Misfire. 71 Random Misfire. 72 TWC Function right hand bank. 73 TWC Function right hand bank. 76 Fuel Injection System Function right hand bank. 77 Rear Heated Oxygen Sensor Circuit. 82 Crankshaft Position Sensor. 84 A/T Diagnosis Communication Line. 85 VTC Solenoid Valve Circuit. 86 Fuel Injection System Function right hand bank. 87 Canister Control Solenoid Valve Circuit. 91 Front Heated Oxygen Sensor Heater Circuit right hand bank. 94 TCC Solenoid Valve. 95 Crankshaft Position Sensor. 98 Engine Coolant Temperature Sensor. 101 Front Heated Oxygen Sensor Heater Circuit right hand bank. 103 Park/Neutral Position Switch Circuit. 105 EGR and EGR Canister Control Solenoid Valve Circuit. 108 Canister Purge Control Valve Circuit So are the codes it is throwing 13, 14, 15? or 23, 24, 25 Last year the speedo stopped working and threw a VSS (14) code, but I've since fixed that, and had the code cleared. So why would it be showing again?