Two-digit EEC codes

Model years 1989 to 1991 used 2-digit codes. 1992-1995 use 3-digit codes. 1996-1999 use 5-digit codes (OBD-II).

Code	KOEO	KOER	Continuous	Check Engine	Description
11					No problems found in this portion of the test
12					Cannot control RPM during self-test high RPM check. Suspect throttle body coking.
13					Cannot control RPM during self-test low RPM check. Suspect idle bypass valve problems.
14					PIP circuit failure. Suspect PIP sensor or TFI module, or grounding or interference problems at the TFI module.
15					ECA ROM test failure.
18					SPOUT circuit open.
19					CID circuit failed.
21					ECT out of self-test range.
22					BP out of self-test range.
23					Throttle position (TP) sensor out of self-test range.
24					Air charge temperature (ACT) sensor out of self-test range.
25					Knock sensor (KS) not sensed during dynamic response test.
26					MAF sensor voltage out of range.
28					Mass air flow (MAF) sensor out of self-test range.
29					Insufficient input from vehicle speed sensor (VSS).
31					Pressure feedback EGR (PFE) circuit below minimum voltage.
32					PFE circuit voltage low.
33					EGR valve opening not detected.
34					PFE sensor voltage out of range.
35					PFE circuit above maximum voltage.
41					HEGO sensor circuit indicates system lean (rear).
42					HEGO sensor circuit indicates system rich (rear).
45					Coil 1 primary circuit failure.
46					Coil 2 primary circuit failure.
48					Coil 3 primary circuit failure.
49					SPOUT signal defaulted to 10 degrees BTDC; SPOUT ciruit open.
51					ECT sensor indicates -40degF; circuit open. Suspect possible shorted ECT, harness.
52					PSPS (Power Steering Pressure Switch) circuit did not change states.
53					TP circuit above maximum voltage. Suspect shorted TP sensor, harness.
54					ACT (Air Charge Temperature) indicated -40degF; circuit open. Suspect shorted sensor, harness.
56					MAF sensor input greater than maximum voltage.
59					Low speed fuel pump circuit open (battery to ECA).
61					ECT indicated 254degF; circuit grounded.
63					TP circuit below minimum voltage. Suspect open TP sensor, harness.
64					ACT indicated 254degF; circuit grounded.
66					MAF sensor input is less than minimum voltage.
67					'89: NPS circuit open; A/C input high.
					'90-91: NPS circuit closed; A/C on.
72					'89: Insufficient BP output change during dynamic response test.
					'90-91: Insufficient MAF output change during dynamic response test.
73					Insufficient TP output change during dynamic response test. Rerun test, goose it harder.
74					BOO (brake on/off) circuit failure during dynamic response test.
75					BOO switch always closed.
77					Brief WOT not sensed during self test; operator error. Rerun test, goose it harder. If this code is received during cylinder balance test, then a TP change was detected- rerun test, making sure not to disturb the throttle as it is running.
79					A/C or defroster on during KOEO.
81					'89: Insufficient IAS output voltage change when solenoid activated.
					'90-91: IAS circuit failure.
82					SCVAC (Speed Control Vacuum) circuit failure (IVSC test).
83					'89: Low speed fuel pump relay circuit open.
					'90-91: Low speed primary fuel pump circuit failure.
84					EVR circuit failure.
85					CANP (Canister Purge) circuit failure.
87					FP primary circuit failure. Suspect inertia switch, fusible link, FP relay.
88					EDF circuit failure.
91					'89: HEGO sensor circuit indicates system lean (front).
					'90-91: No HEGO switching detected (front).
92					HEGO sensor circuit indicates system rich (front).
95					Fuel pump secondary circuit failure.
96					High speed fuel pump relay circuit open.
98					Hard fault present. The PCM is running in FMEM (Failure Effects Management Mode), so something is royally screwed up that the KOEO test should have told you about. Rerun KOEO and fix whatever you find there.