Model years 1989 to 1991 used 2-digit codes. 1992-1995 use 3-digit codes. I have no information on 1996-1997 models; I presume they changed significantly for OBD-II.
| Code | KOEO | KOER | Continuous | Check Engine | Description |
| 111 |  |  |  | | Systems pass. |
| 112 |  |  | |  | Air charge temperature (ACT) sensor indicated 254degF. Circuit grounded. |
| 113 |  |  | | | ACT indicated -40degF. Circuit open. |
| 114 |  |  | | | ACT out of self-test range. |
| 115 |  |  | | | Engine coolant temperature (ECT) sensor out of self-test range. |
| 117 |  | |  |  | ECT indicated 254degF. Circuit grounded. |
| 118 |  | |  |  | ECT indicated -40degF. Circuit open. |
| 121 |  |  |  | | Throttle position (TP) sensor out of self-test range. |
| 122 |  | |  |  | TP sensor circuit below minimum voltage. |
| 123 |  | |  |  | TP sensor circuit above maximum voltage. |
| 124 | | |  | | TP circuit output higher than expected. |
| 125 | | |  | | TP circuit output lower than expected. |
| 126 | | |  | | CID circuit failure. |
| 129 | |  | | | Insufficient mass air flow (MAF) change during dynamic response test. |
| 136 | |  | |  | HEGO sensor indicates system lean (LH). |
| 137 | |  | | | HEGO sensor indicates system rich (LH). |
| 139 | | |  | | No HEGO switching detected (LH). |
| 144 | | |  | | No HEGO switching detected (RH). |
| 157 | |  |  |  | MAF circuit below minimum voltage. |
| 158 |  |  |  | | MAF circuit above maximum voltage. |
| 159 |  |  | | | MAF out of self-test range. |
| 167 | |  | | | Insufficient throttle position change during dynamic response test. |
| 171 | | |  | | No HEGO switching detected / adaptive fuel at limit (RH). |
| 172 | |  |  |  | HEGO sensor indicates system lean (RH). |
| 173 | |  |  | | HEGO sensor indicates system rich (RH). |
| 174 | | |  | | HEGO switching time is slow (RH). |
| 175 | | |  | | No HEGO switching detected / adaptive fuel at limit (LH). |
| 176 | | |  |  | HEGO sensor indicates system lean (LH). |
| 177 | | |  | | HEGO sensor indicates system rich (LH). |
| 178 | | |  | | HEGO switching time is slow (LH). |
| 179 | | |  | | Adaptive fuel lean limit is reached (RH). |
| 181 | | |  | | Adaptive fuel rich limit is reached (RH). |
| 182 | | |  | | Adaptive fuel lean limit is reached at idle (RH). |
| 183 | | |  | | Adaptive fuel rich limit is reached at idle (RH). |
| 184 | | |  | | MAF higher than expected |
| 185 | | |  | | MAF lower than expected |
| 186 | | |  | | Injector pulse width higher than expected. |
| 187 | | |  | | Injector pulse width lower than expected. |
| 188 | | |  | | Adaptive fuel lean limit is reached (LH). |
| 189 | | |  | | Adaptive fuel rich limit is reached (LH). |
| 191 | | |  | | Adaptive fuel lean limit is reached at idle (LH). |
| 192 | | |  | | Adaptive fuel rich limit is reached at idle (LH). |
| 211 | | |  | | PIP circuit fault. |
| 212 | | |  | | IDM circuit failure / SPOUT circuit grounded. |
| 213 | |  | | | SPOUT circuit open. |
| 214 | | |  | | CID circuit failure. |
| 215 | | |  | | Coil 1 primary circuit failure. |
| 216 | | |  | | Coil 2 primary circuit failure. |
| 217 | | |  | | Coil 3 primary circuit failure. |
| 219 | | |  | | SPOUT signal defaulted to 10 degrees BTDC / SPOUT circuit open. |
| 225 | |  | | | Knock sensor (KS) not sensed during dynamic response test. |
| 326 | |  |  | | DPFE circuit voltage lower than expected. |
| 327 |  |  |  | | DPFE output circuit below minimum voltage. |
| 332 | |  |  | | EGR valve opening not detected. |
| 335 |  | | | | DPFE sensor voltage higher or lower than expected. |
| 336 | |  |  | | Exhaust backpressure high / PFE circuit voltage high. |
| 337 |  |  |  | | DPFE output circuit above maximum voltage. |
| 411 | |  | | | Cannot control RPM during self-test low RPM check. |
| 412 | |  | | | Cannot control RPM during self-test high RPM check. |
| 452 | | |  | | Insufficient input from vehicle speed sensor (VSS). |
| 511 |  | | | | EEC processor ROM test failure. |
| 512 | | |  | | EEC processor RAM test failure. |
| 513 |  | | | | Failure in EEC processor internal voltage. |
| 519 |  | | | | PSPS circuit open. |
| 521 | |  | | | PSPS circuit did not change states. |
| 522 |  | | | | Indicates vehicle in gear. |
| 524 |  | |  | | Low speed fuel pump circuit open (battery to ECA). |
| 526 |  | | | | NPS circuit closed; air conditioning on. |
| 536 | |  |  | | BOO circuit failure. |
| 538 | |  | | | Operator error (dynamic response / cylinder balance tests). |
| 539 |  | | | | Air conditioning on / defrost on during KOEO. |
| 542 |  | |  | | Fuel pump secondary circuit failure. |
| 543 |  | |  | | Fuel pump secondary circuit failure. |
| 551 |  | | | | IAS circuit failure. |
| 556 |  | |  | | Fuel pump primary circuit failure. |
| 557 |  | |  | | Low speed primary fuel pump circuit failure. |
| 558 |  | | | | EVR circuit failure. |
| 564 |  | | | | EDF circuit failure. |
| 565 |  | | | | CANP solenoid circuit failure. |
| 565 | |  | | | Hard fault present (FMEM mode). |