If you don't have a OBD2 plug, than it's a OBD1 truck, and you can use the "paperclip method" to pull the codes.
1. Acquire paperclip
2. Open the hood, locate diagnostic plug on the passenger side firewall near the top. It's black and probably 1.5"x3".
3. Open cap to diagnostic plug, on the inside is a schematic of all the pin positions.
4. Remove the little metal jumper in the bottom right of the plug.
5. Get your paperclip, and jump terminals E1 and TE1.
6. Turn key to "ON" but don't start. CEL will blink. Codes are 2 digit, and there's a longer pause in between codes if there's more than one. They repeat indefinitely as long as you leave the ignition on.
Codes List:
OBD1 Codes
1Normal Condition.
2Air Flow Meter signal.
3Ignition signal.
4Engine Coolant Temperature Sensor signal.
5Oxygen Sensor.
6RPM signal (Crank Angle Pulse).
7Throttle Position Sensor signal.
8Intake Air Temperature Sensor signal.
9Vehicle Speed Sensor signal.
10Starter signal.
11Switch signal.
11ECU/ECM.
12Knock Control Sensor signal.
12RPM signal.
13Knock Control CPU (ECM).
13RPM signal.
14Turbocharger Pressure.
14Ignition signal.
21Oxygen Sensor.
22Engine Coolant Temperature Sensor signal.
23Intake Air Temperature Sensor signal.
24Intake Air Temperature Sensor signal.
25Air-Fuel Ratio Lean.
26Air-Fuel Ratio Rich.
27Sub Oxygen Sensor signal.
28No. 2 Oxygen Sensor signal.
31Air Flow Meter signal (Vacuum Sensor signal).
32Air Flow Meter signal.
34Turbocharger Pressure signal.
35Turbocharger Pressure Sensor signal.
35HAC Sensor signal.
41Throttle Position Sensor signal.
42Vehicle Speed Sensor signal.
43Starter signal.
51Switch signal.
52Knock Sensor signal.
53Knock Sensor signal.
54Inter-cooler ECM signal.
71EGR System.
72Fuel Cut Solenoid signal.
78Fuel Pump Control signal.
81TCM Communication.
83TCM Communication.
84TCM Communication.
85TCM Communication.
I have a 1996 FZJ80 and it's OBD2 (US Import, so maybe that's the difference). The OBD2 port would be located in the fusebox in the dash, just above all the fuses.
Good luck!
