| Code | Circuit | When monitored | When placed in memory |
| 11 | Distributor signal circuit | During cranking | If no signal is present since memory was last cleared. |
| 12 | Battery feed to computer | Ignition on | If battery disconnected in last 30-100 engine starts. |
| 13 | MAP sensor, vacuum | From 600 to 1500 rpm | No change in signal between ignition pulses. |
| 14 | MAP sensor, electrical | From 400 to 1500 rpm | MAP sensor above 4.7V or below .02V. |
| 15 | Speed sensor | Decel at closed throttle | If less than 2 mph indicated for over 7-10 seconds on decel. |
| 16 | Battery sense voltage | 1 min after start | Battery voltage drops 4 volts for more then 14 sec. |
| 17 | Cooling system | 12 min after start | Coolant doesn't reach 160 degrees after 8 min. |
| 21 | Oxygen sensor | Temp 170F/ RPM over 1500 | If no rich/lean indicated for 2-12 min. |
| 22 | Coolant sensor | Ignition on | If voltage above 4.96(cold) or below .51(warm) |
| 23 | Charge air sensor | Ignition on | If voltage above 4.96(cold) or below .51(warm) |
| 24 | Throttle P. sensor | Ignition on | If voltage above 4.7 or below .16 |
| 25 | Idle speed motor | Engine at idle | Proper voltage not present, open circuit will not set. |
| 26 | Fuel injectors 1 & 2 | Engine cranking | 85-87; injectors not firing correctly |
| 26 | Injector Drivers | Engine running | 1988; current peak not reached by injectors |
| 27 | Fuel injectors 3 & 4 | Engine cranking | 85-87; injectors not firing correctly |
| 31 | Purge solenoid | Ignition on | Solenoid not turning on and off properly |
| 32 | Power loss lamp | Ignition on | 84-86 lamp not working correctly |
| 33 | A/C relay | Ignition on | Relay not turning on and off properly |
| 34 | EGR solenoid | Ignition on | 84-86; solenoid not turning on and off properly |
| 34 | Speed control | Engine running | 87-88; servo not working properly when cruise is on |
| 35 | Radiator fan relay | Ignition on | Relay not turning on and off properly |
| 36 | Wastegate control | Ignition on | 85-88; solenoid not turning on and off properly |
| 37 | Baro read solenoid | Ignition on | Solenoid not turning on and off properly |
| 41 | Alternator Field | Ignition on | Battery volts to ASD is below 11.75 for more than 22 sec |
| 42 | Auto shutdown relay | Ignition on | Relay not turning on and off properly |
| 43 | Spark control | Ignition on | 84-86; S.C.Interface fails to switch properly |
| 43 | Spark control | During cranking | 87-88; S.C.Interface fails to switch properly |
| 44 | Logic module | Ignition on | 84 only wrong PROM in logic module |
| 44 | Battery temp voltage | During cranking | 85-87; sensor signal above 4.9 or below .04 |
| 44 | Fused J-2 | Ignition on | 88; J2 not present to logic module in SMEC |
| 45 | Overboost monitor | Engine running | Boost out of predetermined range |
| 46 | Battery volt sensing | Engine running | Battery volts 1 volt above desired for more than 25 sec |
| 47 | Battery volt sensing | Engine running/160F | Battery volts 1 volt below desired for more than 35 sec |
| 51 | Oxygen sensor | Engine running/closed loop | 84 rich/lean more than 2 min/85-88 lean more than 12 min |
| 52 | Oxygen sensor | Engine running/closed loop | 85-88 rich more than 12 min |
| 52 | Logic module failure | Ignition on | 84 Logic module failure |
| 53 | Logic module failure | Ignition on | 85-86 Logic module failure |
| 54 | Dist.Sync.pickup | Engine running | No signal at logic module |