GM OBD1 and OBD2 Codes Full List for Free Download

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Do you drive a Chevy model ranging between 1982-1995? Are you curious about how to read, interpret the OBD1 codes for your GM car? 

Reading trouble codes in your GM vehicle could be easier than toasting your bread. In fact, if you’re reading the trouble codes without the help of a scanner, the only necessary requirement is an unrolled paper clip. 

Towards the end of the article, you will be capable of performing a self-diagnostic test with or without a scanner. You will learn to read the trouble codes, interpret them, and identify the faulty component or sensor. Additionally, you get to clear the trouble codes at the comfort of your garage with little sweat and with less or no penny spent. 

Keep reading to find out more!

GM OBD1 Codes Full List

Free Download: GM OBD1 Code List FULL (PDF)

CodesMeaning/Fault Location
12No distributor reference pulse (diagnostic test active)
13Oxygen sensor circuit open or no activity
14Engine coolant temp sensor error (high temp indicated)
15Engine coolant temp sensor error (low temp indicated)
16System voltage too low
17Camshaft position sensor error
21Throttle Position sensor error (signal high)
22Throttle position sensor error (signal low)
23Intake air temp sensor error (low temp indicated)
24Vehicle speed sensor error (open circuit or no activity)
25Intake air temp sensor error (high temp indicated)
26Quad Driver Module (QDM A) error
28Auto transmission range pressure switch error
31Waste gate solenoid circuit error
31Gear Position Switch (PRNDL) error
32Baro sensor circuit error/ EGR circuit error/ MAP sensor signal open
33MAP sensor circuit error (signal high indicating low vacuum)
34MAP sensor circuit error (signal low indicating high vacuum)
35IAC problem or idle error
36MAF sensor error/ 24x crankshaft position sensor circuit error/ 4T60-E shifting error
37TCC brake switch circuit error
38TCC brake switch circuit error
39Clutch switch circuit error/ Torque converter clutch error
41Ignition control error/ MEM-CAL error/ Computer Controlled Ignition Cam Sensor Signal error
42Ignition bypass circuit error
43Knock sensor error
44Oxygen sensor error (lean condition indicated)
45Oxygen sensor error (rich condition indicated)
46Pass-Key II (VATS) system error - circuit out of freq range
47UART (serial data) circuit error
51PROM error/ Incorrect MEM-CAL
52Fuel cal-pak incorrect or missing
53System voltage too high
53Digital EGR Valve solenoid 1 error
54Fuel pump circuit low voltage/ Digital EGR Valve solenoid 2 error
55ECM error/Digital EGR Valve solenoid 3 error
56Quad Driver Module (QDM B) error
57Boost Control error
58Trans fluid temp sensor circuit error (low voltage)/ VATS system error
59Trans fluid temp sensor circuit error (high voltage)
61A/C system performance
63Right bank O2 sensor circuit error/ MAP sensor circuit signal voltage high (low vacuum indicated)
64Right bank O2 sensor lean exhaust indicated/ MAP sensor circuit signal voltage low (high vacuum indicated)
65Right bank O2 sensor rich exhaust indicated
66A/C pressure sensor circuit error (low pressure indicated)
67A/C pressure sensor circuit error
68A/C clutch relay circuit error (shorted to ground)
69A/C clutch relay circuit error (open circuit indicated)/ A/C high pressure switch error
70A/C pressure sensor circuit error (high pressure indicated)
71A/C evaporator temp sensor circuit error (low temp indicated)
72VSS signal circuit error
73A/C evaporator temp sensor circuit error (high temp indicated)
75Digital EGR solenoid #1 circuit error
76Digital EGR solenoid #2 circuit error
77Digital EGR solenoid #3 circuit error
79Transmission fluid over temp
80Transmission component slipping
823x Crankshaft position sensor circuit error
85PROM error
86ECM Analog/Digital error
87EEPROM error (flash memory error)
90TCC error
93Transmission pressure control solenoid circuit error
96Transmission system voltage low
98Invalid PCM program
99Invalid PCM program

GM Manufacturer-specific OBD2 Codes Full List

Free Download: GMManufactured-Specific OBD2 Code List FULL (PDF)

NOTE: For some code numbers, there may be more than one definition because the same number may be used for different faults on different model years or models.
P1031 - O2 Sensor heater control circuit problem
P1105 - Secondary Vacuum Sensor circuit
P1106 - MAP sensor circuit voltage intermittent high or low
P1107 - MAP sensor voltage intermittent low
P1108 - BARO to MAP sensor circuit comparison too high
P1109 - Secondary port throttle system
P1111 - Intake Air Temperature Sensor circuit intermittent high voltage
P1112 - Intake Air Temperature Sensor circuit intermittent low voltage
P1113 - Intake Resonance Switchover Valve Control
P1114 - Engine Coolant Temperature intermittent high or low
P1115 - Engine Coolant Temperature intermittent high or low
P1116 - Engine Coolant Temperature erratic
P1117 - Engine coolant temperature below minimum voltage/254 F
P1118 - Engine coolant temperature above maximum voltage/-40 F
P1119 - Engine coolant temperature out of range
P1120 - Throttle position sensor 1 circuit
P1121 - Ignition control module 4X circuit, or TPS out of range
P1122 - Ignition control module 4X circuit, or TPS out of range
P1125 - Average Pump Period system, or pedal position system
P1133 - A/C pressure sensor high voltage, or O2 sensor bank 1 sensor 1 sluggish
P1134 - 5 volt reference 2 voltage low, or O2 sensor bank 1 sensor 1
P1135 - O2 Sensor 1 bank 1 reading lean, or 4/5 shift solenoid stuck on
P1136 - 5 volt reference 2 circuit, or O2 sensor bank 1 sensor 1 rich
P1137 - O2 Sensor low voltage during power enrichment
P1138 - O2 Sensor high voltage during decel fuel cutoff
P1139 - Brake booster vacuum sensor (low vacuum)
P1139 - O2 Sensor insufficient switching (Bank 1 Sensor 2)
P1140 - O2 Sensor Sluggish (Bank 1 Sensor 2)
P1141 - O2 Sensor Heater Control circuit (Bank 1 Sensor 2)
P1143 - O2 Sensor reading lean or low voltage (Bank 1 Sensor 3)
P1144 - O2 Sensor reading rich or high voltage (Bank 1 Sensor 3)
P1145 - O2 Sensor sluggish (slow crosscounts) (Bank 1 Sensor 3)
P1153 - A/C pressure sensor low voltage
P1153 - O2 Sensor low switching (Bank 2 Sensor 1)
P1154 - O2 Sensor low transition time (Bank 2 Sensor 1)
P1155 - A/C evap temperature switch high voltage
P1155 - O2 Sensor reading lean (Bank 2 Sensor 1)
P1156 - A/C high pressure switch high voltage
P1156 - O2 Sensor reading rich (Bank 2 Sensor 1)
P1157 - O2 Sensor rich or high voltage (Bank 2 Sensor 2)
P1158 - O2 Sensor rich or high voltage (Bank 2 Sensor 2)
P1158 - Engine overtemperature protection fault
P1159 - O2 Sensor crosscounts (Bank 2 Sensor 2)
P1161 - O2 Sensor heater control circuit (Bank 2 Sensor 2)
P1163 - O2 Sensor reading lean or low voltage (Bank 2 Sensor 3)
P1164 - O2 Sensor reading rich or high voltage (Bank 2 Sensor 3)
P1165 - O2 Sensor crosscounts (Bank 2 Sensor 3)
P1170 - Bank to bank fuel trim offset
P1171 - Fuel system lean during acceleration
P1185 - Engine Temperature Sensor circuit
P1186 - Engine Oil Temperature circuit performance
P1187 - Engine Oil Pressure Sensor circuit low voltage
P1188 - Engine Oil Pressure Sensor circuit voltage high
P1189 - Engine Oil Pressure Switch circuit
P1190 - Vacuum leak
P1191 - Intake air duct leak
P1200 - Injector control circuit
P1211 - Mass Airflow circuit intermittent high
P1212 - Mass Airflow circuit intermittent low
P1214 - Injection Pump Timing Offset
P1215 - Ground fault detection indicated (generator driver circuit)
P1216 - Fuel Solenoid response time too short
P1217 - Fuel Solenoid response time too long
P1218 - Injection Pump calibration circuit
P1219 - Throttle Position Sensor reference voltage
P1220 - Throttle Position Sensor circuit fault
P1221 - Fuel pump second circuit low
P1121. . Throttle position sensor circuit performance
P1222 - Injector circuit cylinder 1 intermittent
P1225 - Injector circuit cylinder 2 intermittent
P1228 - Injector circuit cylinder 3 intermittent
P1231 - Injector circuit cylinder 4 intermittent
P1234 - Injector circuit cylinder 5 intermittent
P1237 - Injector circuit cylinder 6 intermittent
P1240 - Injector circuit cylinder 7 intermittent
P1243 - Injector circuit cylinder 8 intermittent
P1250 - Early fuel evaporation heater circuit
P1257 - Boost Control fault, or supercharger overboost
P1258 - Engine overtemperature protection, or low coolant fuel disable
P1260 - Fuel Pump Speed Relay control circuit, or last test failed speed control circuit
P1271 - Accelerator Pedal Position Sensor 1-2 correlation
P1272 - Accelerator Pedal Position Sensor 2-3 correlation
P1273 - Accelerator Pedal Position Sensor 1-3 correlation
P1274 - Injection wiring incorrect
P1275 - Acceleration position sensor 2 circuit, or boost control
P1276 - Accelerator Pedal Positioning Sensor 1 circuit
P1280 - Accelerator Pedal Positioning Sensor 2 circuit
P1281 - Accelerator Pedal Positioning Sensor 2 circuit out of range
P1285 - Accelerator Pedal Positioning Sensor 2 circuit
P1286 - Accelerator Pedal Positioning Sensor 2 circuit out of range
P1300 - Ignition coil 1 primary feedback circuit
P1305 - Ignition Coil 2 primary feedback circuit
P1310 - Ignition Coil 3 primary feedback circuit
P1315 - Ignition Coil 4 primary feedback circuit
P1320 - Distributorless ignition 4X signal intermittent
P1321 - Electronic ignition system fault
P1322 - Electronic ignition system control missing
P1323 - Loss of high resolution rpm signal
P1324 - Crank rpm too low
P1335 - Crankshaft positioning sensing circuit
P1336 - Crankshaft position system variation not learned
P1345 - Camshaft to crankshaft position correlation fault
P1346 - Crankshaft sensor system variation not learned, or intake camshaft position out of range
P1349 - Intake Camshaft position system
P1350 - Ignition control system
P1351 - Ignition control circuit voltage high
P1351 - Ignition control circuit open
P1352 - Bypass circuit open or voltage high
P1353 - Ignition control output high/pulse detected when ground cylinder #3
P1354 - Ignition control output high/pulse detected when ground cylinder #4
P1355 - Ignition control output high/pulse detected when ground cylinder #5
P1356 - Ignition control output high/pulse detected when ground cylinder #6
P1357 - Ignition control output high/pulse detected when ground cylinder #7
P1358 - Ignition control output high/pulse detected when ground cylinder #8
P1359 - Ignition Coil group 1 control circuit
P1360 - Ignition Coil group 2 control circuit
P1361 - Ignition control cylinder #1 not toggling after enable,or low voltage
P1362 - Ignition control cylinder #2 not toggling after enable,or low voltage, or bypass circuit shorted or low voltage
P1363 - Ignition control cylinder #3 not toggling after enable,or low voltage
P1364 - Ignition control cylinder #4 not toggling after enable,or low voltage
P1365 - Ignition control cylinder #5 not toggling after enable,or low voltage
P1366 - Ignition control cylinder #6 not toggling after enable,or low voltage
P1367 - Ignition control cylinder #7 not toggling after enable,or low voltage
P1368 - Ignition control cylinder #8 not toggling after enable, or low voltage
P1370 - Too many ignition reference pulses
P1371 - Too few ignition reference pulses
P1372 - Crankshaft Position Sensor A-B correlation
P1374 - Crankshaft position sensor, 3X Reference circuit
P1375 - 24X Reference circuit voltage too high
P1376 - Reference voltage low, or ignition ground circuit
P1377 - Ignition control module CAM pulse to 4X reference pulse comparison
P1380 - ABS rough road/misfire diagnosis prevented
P1381 - Misfire detected, no EBCM/PCM serial data
P1401 - Exhaust Gas Recirculation flow test fault
P1403 - Exhaust Gas Recirculation Solenoid 1 error
P1404 - Exhaust Gas Recirculation Solenoid 2 error
P1405 - Exhaust Gas Rrecirculation Solenoid 3 error
P1406 - Exhaust Gas Recirculation pintle position error
P1407 - EGR valve air leak
P1408 - EGR valve vacuum failure
P1409 - EGR valve vacuum leak
P1410 - EGR valve vacuum restriction, or fuel tank pressure system
P1415 - AIR system Bank 1
P1416 - AIR system Bank 2
P1431 - Fuel Level Sensor 2 circuit
P1432 - Fuel Level Sensor 2 circuit low voltage
P1433 - Fuel Level Sensor 2 circuit voltage high
P1441 - EVAP Canister continuous open purge flow,or high voltage during non-purge
P1442 - EVAP monitor circuit/vacuum switch high voltage
P1450 - Barometric Pressure Sensor (BARO) circuit
P1451 - Barometric Pressure Sensor performance
P1460 - Cooling Fan control system, or misfire detected (Catera only)
P1483 - Engine cooling system performance
P1500 - Starter signal circuit
P1501 - Vehicle speed sensor circuit intermittent, or Theft deterrent system
P1502 - Theft deterrent system no password received
P1503 - Theft deterrent system password improper
P1508 - Idle Air Control system — idle too low
P1509 - Idle Air Control system — idle too high
P1510 - Backup power supply
P1511 - Throttle Control System – backup system performance
P1514 - Airflow to throttle position sensor too high
P1515 - Electronic throttle module throttle position
P1516 - Electronic throttle module throttle postion
P1517 - Electronic throttle module, or TAC module fault
P1518 - No communication between electronic throttle module and PCM
P1519 - Throttle Actuator Control Module
P1520 - Park/Neutral Switch circuit, gear indicator system
P1523 - Electronic throttle control throttle return
P1524 - Throttle Position Sensor out of range or misadjusted
P1525 - Throttle Body Service required
P1526 - Throttle position learn process not complete
P1527 - Transmission range/pressure switch comparison
P1528 - Governor control system
P1530 - Ignition timing adjustment switch circuit, or A/C Refrigerant Pressure Sensor error
P1531 - A/C low refrigerant
P1532 - Engine coolant temperature sensor intermittent, or A/C Evaporator Temperature circuit low voltage
P1533 - A/C Low Side Temperature Sensor circuit
P1535 - A/C High Side Temperature Sensor circuit
P1536 - A/C system ECT over-temperature
P1537 - A/C request circuit voltage low
P1538 - A/C request circuit voltage high
P1539 - A/C High Pressure Switch circuit voltage high
P1540 - A/C system high pressure
P1542 - A/C system high pressure or high temperature
P1543 - A/C system performance out of range
P1545 - A/C Clutch Relay Control circuit
P1546 - A/C Clutch Relay control circuit voltage low
P1550 - Cruise control, motor actuator circuit
P1554 - Speed Control status circuit
P1555 - Electric Variable Orifice fault (Saturn)
P1558 - Speed Control (SPS low)
P1560 - Speed Control System/Transaxle not in Drive
P1561 - Speed Control Vent Solenoid
P1562 - Speed Control Vacuum Solenoid
P1564 - ECM battery voltage loss (Catera only), or speed control system/vehicle acceleration too high
P1565 - Speed Control Servo Position Sensor
P1566 - Speed Control System/Engine RPM too high
P1567 - Speed Control Master Switch
P1568 - Speed Control (SPS high)
P1570 - Speed Control System/Traction Control active
P1571 - Traction Control System desired torque circuit
P1572 - Traction Control System active circuit voltage low too long
P1573 - PCM/EBTCM serial data circuit communication malfunction
P1574 - EBTCM system/stop lamp circuit voltage high
P1575 - Stop lamp control circuit (97-98 Corvette only), or extended travel brake switch circuit voltage high
P1576 - Brake Booster Vacuum Sensor circuit voltage high
P1577 - Brake Booster Vacuum Sensor circuit voltage low
P1578 - Brake Booster Vacuum Sensor circuit low vacuum
P1579 - Park/Neutral to Drive/Reverse at high throttle angle
P1580 - Cruise Control Module move circuit, low voltage
P1581 - Cruise Control Module move circuit, high voltage
P1582 - Cruise Control Module direction circuit, low voltage
P1583 - Cruise Control Module direction circuit, high voltage
P1584 - Cruise control disabled
P1585 - Cruise Control inhibit output circuit
P1586 - Cruise Control Brake Switch 2 circuit
P1599 - Engine stall detected
P1600 - Powertrain control module battery, or loss of communication between PCM and TCM
P1601 - ECM over-temperature
P1602 - PCM to ABS module communication problem
P1603 - Serial data communication problem
P1604 - IPC Serial data communication problem
P1605 - Serial data communication problem with HVAC module
P1607 - Engine Oil Level Switch circuit
P1610 - Loss of PZM serial data, or failure of body function controller (1997 Cutlass & Malibu only)
P1611 - Loss of CVRTD serial data
P1617 - Engine Oil Level Switch circuit
P1619 - Engine Oil Life Monitor reset circuit, or oil life error
P1620 - Engine coolant low (Saturn)
P1621 - Powertrain control module memory error, or VCM EEPROM performance (1998 5.7L only)
P1623 - PCM Prom error, or Transaxle Temperature Sensor fault (Saturn)
P1624 - Powertrain control module software reset, or customer snapshot data available (Saturn)
P1625 - Powertrain control module system reset, or TCM flash checksum fault (Saturn)
P1626 - Anti-theft system fuel enable circuit (Passkey error)
P1627 - A/D performance, or Powertrain Control Module fault
P1628 - PCM Engine Control Temperature Pull-up Resistor, or Engine Coolant Temperature Sensor circuit resistor fault
P1629 - Anti-theft divide cranking signal or Passkey cranking error
P1630 - System voltage too high/too low, or ECM immobilizer learning mode (Cavalier & Monte Carlo only)
P1631 - Oxygen sensor #1 slow response, or anti-theft password incorrect
P1632 - Anti-theft fuel disable signal received
P1633 - Ignition power circuit low voltage
P1634 - Ignition power circuit low voltage
P1635 - 5 volt reference voltage to sensors low
P1636 - Powertrain control module fault
P1637 - Alternator warning lamp control signal “L” terminal problem
P1638 - Alternator Field (F) terminal circuit
P1639 - Powertrain Control Module 5 volt reference voltage low
P1640 - Powertrain control module fault
P1641 - EVAP fuel tank pressure sensor circuit voltage high, or fan 1 relay control circuit, or MIL light circuit, or A/C compressor clutch relay circuit
P1642 - Fan control relay, or vehicle speed sensor output, or secondary air injection relay fault (96 Lumina/Monte 3.4L)
P1643 - Powertrain control module fault
P1644 - Throttle position sensor circuit, or traction control fault
P1645 - Boost control solenoid circuit, or EVAP solenoid output circuit
P1646 - Powertrain control module fault (quad driver 1)
P1647 - Powertrain control module fault (quad driver 1)
P1650 - Powertrain control module fault (quad driver 2)
P1651 - Powertrain control module fault (quad driver 2), or cooling fan relay 1
P1652 - Cooling fan relay 2, or suspension control module (Cadillac only)
P1653 - Traction control circuit (Pontiac), or fuel gauge control circuit (Chevy except Caprice), or engine oil level warning lamp (Caprice & 99 Olds Silhouette only)
P1654 - A/C relay circuit, or cruise control disable output circuit
P1655 - Powertrain control module fault (quad driver 2), or EVAP canister purge valve
P1656 - Powertrain control module fault (quad driver 2), or wastegate solenodi control circuit (turbo models only)
P1657 - Powertrain control module fault (quad driver 2), or skip shift solenodi control circuit
P1660 - Cooling fan circuit,or powertrain control module fault
P1661 - EVAP fuel tank pressure sensor circuit, or Check Engine Light circuit, or PCM quad driver fault
P1662 - PCM quad driver fault, or cruise control circuit
P1663 - Alternator warning lamp circuit, or oil change warning lamp circuit
P1664 - Powertrain control modeul fault (quad driver 3), or fuel cutoff solenoid
P1665 - Powertrain control module fault (quad driver 3), or EVAP canister vent valve
P1667 - Powertrain control module fault (quad driver 3), or reverse inhibit solenoid control circuit
P1670 - Powertrain control module fault (quad driver 4)
P1671 - Malfunction Indicator Lamp (MIL) circuit fault
P1672 - Powertrain control module fault (quad driver 4), or low engine oil level lamp control circuit
P1673 - Powertrain control module fault (quad driver 4), or engine hot lamp control circuit
P1674 - Powertrain control module fault (quad driver 4), or tachometer control circuit
P1675 - EVAP vent solenoid control circuit
P1676 - Powertrain control module fault (quad driver 4), or EVAP canister vent valve
P1677 - Powertrain control module fault (quad driver 4)
P1680 - Powertrain control module fault
P1681 - Powertrain control module fault
P1682 - Powertrain control module fault
P1683 - Powertrain control module fault
P1684 - Powertrain control module fault
P1685 - Powertrain control module fault
P1686 - Powertrain control module fault
P1687 - Powertrain control module fault
P1689 - Traction Control System delivered torque control circuit
P1690 - Powertrain control module loop overrun
P1691 - Coolant gauge circuit voltage low
P1692 - Coolant gauge circuit voltage high
P1693 - Tachometer circuit voltage low
P1694 - Tachometer circuit voltage high
P1695 - Remote keyless entry circuit
P1696 - Remote keyless entry circuit
P1700 - Malfunction Indicator Lamp requested by trans control module
P1701 - Malfunction Indicator Lamp request circuit
P1740 - Torque control/management request circuit
P1760 - Transmission Control Module supply voltage interrupted
P1780 - Park/Neutral Position Switch circuit
P1781 - Engine torque signal circuit
P1792 - ECM to Transmission Control Module engine coolant signal
P1800 - ECM to Transmission Control Module engine coolant signal
P1810 - ATF pressure manual valve powition switch malfunction
P1811 - Long shift and maximum adaptation limit reached
P1812 - TOT condition
P1814 - Torque converter clutch (TCC) overstress
P1819 - Transmission range switch out of range, possible no start
P1820 - Transmission range switch A voltage low
P1822 - Transmission range switch B voltage high
P1823 - Transmission range switch P voltage low
P1825 - Transmission range switch A, B, C & P signals invalid
P1826 - Transmission range switch C voltage high
P1835 - Kickdown Switch circuit
P1842 - 1-2 Shift Solenoid circuit low input
P1843 - 1-2 Shift Solenoid circuit high input
P1845 - 2-3 Shift Solenoid circuit low input
P1847 - 2-3 Shift Solenoid circuit high input
P1850 - Brake Band Aply Solenoid
P1860 - Torque Converter Clutch (TCC) PWM Solenoid circuit
P1864 - TCC Enable Solenoid circuit
P1868 - Transmission Fluid life
P1870 - Transmission component slipping
P1873 - Oxygen sensor bank 2 sensor 2 crosscounts
P1874 - Oxygen sensor bank 1 sensor 3 crosscounts
P1875 - 4WD Low Switch circuit electrical
P1886 - Transaxle Shift, Timing Solenoid performance
P1887 - TCC Release Switch malfunction
P1890 - Throttle Position signal input
P1891 - Throttle position sensor circuit signal low
P1892 - Throttle position sensor circuit signal high
P1895 - Engine torque delivered circuit

How to Read OBD1 Codes for GM with a Paper Clip

Do you ever get frustrated with why the check engine light keeps flashing on your vehicle, or do you just want to know the fault causing you much discomfort and disturbance while driving? Here are the steps to follow to diagnose the faulty system in your Chevy vehicle:

  1. First, locate the diagnostic plug underneath the dashboard. It should include 10 female pins and has a black plastic casing. 
  2. Unroll a paper clip and fold it into a U or V shape. 
  3. Insert the ends of the unrolled paper clip through pins A and B, which are the two top right pins on the plug. These steps automatically shift the vehicle to diagnostic mode. 
  4.  Next, start the ignition but be careful not to start the engine. 
  5. Fix your eyes on the instrument cluster. Your primary focus should be the check engine light which should start blinking at any moment. 
  6. The diagnostic systems communicate via iterative blinking of the check engine light. Counting the number of blinks should tell you the error code.
  7. The vehicle groups error codes in 2 digits and each is iterated 3 times. 
  8. The first time the vehicle will blink once, pause, then twice to symbolize code 12. This code means the start of the diagnosis. The code is repeated thrice before trouble codes begin displaying. 
  9. The vehicle will iterate through the error codes, which you should record with a pen and paper, then finish with a code 12 indicating the end of the process.
  10. Turn the ignition off and pull out the paper clip before looking up the meaning of the codes in Google. 

How to Read OBD1 Codes on GM with a Scanner

Why improvise when you could get a scanner to perform the same function as the paper clip. GM scanners help in reading the error codes without jeopardizing the system’s electronic circuitry. Here is how to use it:

  1. Insert the scanner onto the diagnostic plug, which should be located beneath the dashboard. Ensure that it is inserted correctly for its pins to mesh with the plug’s pins A and B. 
  2. Turn on the ignition but be careful not to rev up the engine. 
  3. Check the check engine light. It should flash once then twice, indicating a code 12 that represents the start of diagnostic mode. Each code will be iterated thrice. 
  4. Next, the check engine light will flash several times to indicate the trouble codes. You should note and record them with a piece of paper and pen. It would help if you got a partner to assist by writing down the codes or counting the number of flashes that you might miss if you did the work on your own.
  5. After the system displays all the error codes, it will flash a code 12 indicating the end of the diagnosis. 
  6. Switch off the ignition.
  7. Look up the error code in Google for clarity of the faulty component. Or you could come back to this page after this procedure and look it down below in our GM OBD1 code list. 

READ MORE: Generic OBD2 Codes List for All Cars [Updated 2021]

How to Clear GM OBD1 Codes

GM OBD1 codes are super easy to remove. You don’t have to do anything at times, and starting your car three or four times will eliminate the trouble codes. Nevertheless, there is a quicker method that is also relatively easy to execute. Here is how to do it:

  1. Locate the battery in your car, which should be located somewhere underneath the engine compartment. 
  2. Using a wrench, loosen the bolt reinforcing the plug to the negative terminal. The negative terminal should have a minus symbol on it, and a black cable should be mounted using a plug on it. 
  3. Disconnect the cable from the negative terminal.
  4. Wait for 30 to 60 seconds before reconnecting the cable to the negative terminal. 
  5. Tighten the bolt with the wrench.
  6. Turn on the ignition and check if the error code is removed.
  7. If the check engine light is still flashing, repeat the above procedure a second time, only that this time you wait for 1 to 2 minutes. 

READ MORE: Best GM Scan Tools 2021 [Review and Comparison]

Final Thought

Flashing engine light doesn’t have to frustrate or distract you while you can quickly identify the fault within your vehicle. Best of all, you won’t have to spend a dime with the DIY techniques mentioned in the post.

By looping with a paper clip through pin A and B for the diagnostic plug, you can count the number of flashes displayed by the check engine light to identify the trouble code. Or even better, you could get an excellent scanner, and you don’t have to worry about looping through the wrong terminal. Counting the number of flashes will reveal the trouble codes in your vehicle.

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