GM generic codes for OBD1 (for vehicles made before 1995)
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    12 System normal
    13 oxygen sensor circuit open
    14 coolant sensor high resistance or shorted
    15 coolant sensor circuit low or open
    16 direct ignition system (DIS) fault in circuit
    17 cam position sensor fault
    18 crank or cam sensor error
    19 crank sensor circuit fault
    21 tps sensor out of range
    22 tps sensor signal voltage low
    23 intake air temp sensor out of range, low
    24 vehicle speed (vss) sensor circuit fault
    25 air temp sensor sensor out of range, high
    26 quad-driver module (computer) circuit #1 fault
    27 quad-driver module (computer) 2nd gear circuit
    28 quad-driver module (computer) circuit #2 fault
    29 quad driver module (computer) 4th gear circuit
    31 cam position sensor fault
    32 egr circuit fault
    33 map sensor signal out of range, high
    34 map sensor signal out of range, low
    35 idle air control sensor circuit fault
    36 ignition system circuit error
    38 brake input circuit fault
    39 clutch input circuit fault
    41 cam sensor circuit fault, igntion control circuit fault
    42 electronic spark timing (EST) circuit grounded
    43 knock sensor
    or electronic spark control circuit fault
    44 oxygen sensor lean exhaust
    45 oxygen sensor rich exhaust
    46 pass-key II circuit or ps.pressure switch circuit fault
    47 pcm-bcm data circuit
    48 misfire diagnosis
    51 calibration error, mem-cal, ecm or eeprom failure
    52 engine oil temperature circuit, low temperature indicated
    53 battery voltage error or egr or pass-key II circuit
    54 egr system failure or fuel pump circuit low voltage
    55 a/d converter error or pcm not grounded or lean fuel or frounded reference voltage
    56 quad-driver module #2 circuit
    57 boost control problem
    58 vehicle anti-theft system fuel enable circuit
    61 a/c system performance or degraded oxygen sensor signal
    62 engine oil temperature high temperature indicated
    63 oxygen sensor right side circuit open or map sensor out of range
    64 oxygen sensor right side lean exhaust indicated
    65 oxygen sensor right side rich exhaust indicated
    66 a/c pressure sensor circuit low pressure
    67 a/c pressure sensor circuit or a/c clutch circuit failure
    68 a/c compressor relay circuit failure
    69 a/c clutch circuit head pressure high
    70 a/c refrigerant pressure circuit high
    71 a/c evaporator temperature sensor circuit low
    72 gear selector switch circuit
    73 a/c evaporator temperature circuit high
    75 digital egr #1 solenoid error
    76 digital egr #2 solenoid error
    77 digital egr #3 solenoid error
    79 vehicle speed sensor (vss) circuit signal high
    80 vehicle speed sensor (vss) circuit signal low
    81 brake input circuit fault
    82 ignition control (IC) 3X signal error
    85 prom error
    86 analog/digital ecm error
    87 eeprom error
    99 power management                                                                                                                                                                                                                                                                                                                                                                                                                                                                                              
Ford generic codes for OBD1 (vehicles made before 1995)


11 system pass
12 idle control fault
13 dc motor did not move
14 engine rpm signal fault or PIP circuit failure
15 eec processor or power to KAM interrupted
16 rpm to low to check oxygen sensor test or fuel control error
17 cfi fuel control system fault or rich/lean condition indicated
18 ignition diagnostic monitor (IDM) circuit failure
19 cylinder identification (CID) sensor input failure
21 engine coolant temperature (ECT) out of self-test range
22 manifold absolute pressure (MAP) sensor circuit out of range
23 throttle positioner sensor out of self-test range
24 air charge temperature (ACT) sensor out of self-test range
25 knock not sensed during dynamic response test
26 transmission fluid temperature out of self-test range
28 loss of primary tach, right side
29 insufficient input from vehicle speed sensor
31 egr positioner sensor below minimum voltage
32 egr positioner sensor below closed limit
33 throttle positioner sensor noisy/harsh on line
34 egr valve circuit out of self-test range
35 egr valve circuit above maximum voltage
38 idle track switch circuit open
39 axod torque converter or bypass clutch not applying properly
41 oxygen sensor circuit indicates system always lean
42 oxygen sensor circuit indicates system always rich
43 oxygen sensor out of self-test range
44 air injection control system failure
45 coil 1 primary circuit failure
46 coil primary circuit failure
47 4X4 switch is closed or oxygen sensor failure
48 coil primary circuit failure
49 electronic transmission shift error
51 engine coolant temperature sensor circuit open
52 power steering pressure switch circuit open
53 throttle position circuit above maximum voltage
54 air charge temperature circuit open
55 key power input to processor open circuit
56 mass air flow circuit above maximum voltage
57 axod circuit failure
58 idle tracking switch circuit fault
59 automatic transmission shift error
61 engine coolant temperature circuit grounded
62 converter clutch error
63 throttle positioner circuit below minimum voltage
64 air charge temperature circuit grounded
65 charging system
over voltage
66 mass air flow sensor circuit below minimum voltage
67 neutral/drive switch circuit open
68 transmission fluid temperature over temperature range69 transmission shift error
70 data circuit communication link circuit failure
71 message center circuit circuit failure
72 insufficient manifold absolute pressure (MAP) change during dynamic response test
73 insufficient throttle positioner (TPS) change during dynamic response test
74 brake on/off (BOO) circuit open
75 brake on/off (BOO) circuit closed
76 insufficient air flow output change during test
77 brief wide open throttle not sensed during test
78 power interrupt detected
79 a/c on/defrost on during self test
81 map has not changed normally
82 super charger bypass circuit failure
83 OIC-low speed fuel pump relay circuit failure
84 egr vacuum regulator (EVR) circuit failure
85 canister purge circuit failure
86 shift solenoid circuit failure
87 fuel pump circuit failure
88 electro drive fan circuit failure
89 transmission solenoid circuit failure
91 no oxygen sensor switching detected
92 shift solenoid circuit failure
93 throttle positioner sensor input low
94 torque converter clutch solenoid circuit failure
95 fuel pump secondary circuit failure
96 fuel pump secondary circuit failure
97 transmission indicator circuit failure
98 electronic pressure control circuit failure

99 eec has not learned to control idle