Codes.. for 1988-91 Vin # C bonnevilles
12 - Diagnostic Mode
13 - Oxygen Sensor Circuit( Open Circuit )
14 - Coolant Temperature Sensor Circuit( High Temperature Indicated )
15 - Coolant Temperature Sensor Circuit ( Low Temperature Indicated )
16 - System High Voltage
21 - Throttle Position Sensor Circuit ( Signal Voltage High )
22 - Throttle Position Sensor Circuit ( Signal Voltage Low )
23 - Intake Air Temperature Sensor Circuit ( Low Temperature Indicated )
24 - Vehicle Speed Sensor Circuit
25 - Intake Air Temperature Sensor Circuit ( High Temperature Indicated )
26 - Quad Driver Circuit
27 - Gear Switch Diagnosis( Second Gear Switch )
28 - Gear Switch Diagnosis ( Third Gear Switch )
29 - Gear Switch Diagnosis ( Fourth Gear Switch )
31 - Park/Neutral Switch Circuit
34 - Mass Air Flow Sensor Circuit ( Grams Per Second / Low )
38 - Brake Input Circuit
39 - Torque Converter Clutch Circuit
41 - Cam Sensor Circuit
42 - Electronic Spark Timming Circuit
43 - Electronic Spark Control Circuit
44 - System Lean
45 - System Rich
46 - Power Steering Pressure Switch Circuit
48 - Misfire Diagnosis
51 - MEM-CAL ERROR ( Faulty or Incorrect MEM-CAL )
63,64,65 - Exahust Gas Recirculation Flow Check