OBD1 Codes – Trouble Code List & reading (GM)
Did you own a GM car from 1980-1995? There is a good chance that your vehicle has an OBD1 connector.
It is unique, it works on Pontiac Chevrolet GMC Oldsmobile Cadillac and Buick. You can use the OBD1 connector to read trouble codes from your vehicle at home, without needing any diagnostic tools.
These connectors can be read without the use of special diagnostic tools.
OBD2 codes are found in newer cars after 1996. This article won't apply to them. Our other OBD2 code article is available.
Check out the OBD1 Trouble Codes List
This is an exhaustive OBD1 trouble code listing. The OBD1 codes’ meanings can differ a bit depending on what car model you have, but most of them are the same among all car manufacturers. These codes are not to be considered as a warranty. For the specific trouble codes for your vehicle model, check your manual.
| Code | Description |
|---|---|
| 12 | System OK (Diagnosis mode activate ) |
| 13 | Oxygen O2 Sensor – Circuit open/no activity |
| 14 | Coolant Temperature sensor – Resistance too high or shorted circuit |
| 15 | Coolant Temperature Sensor – Circuit low or open |
| 16 | Direct ignition system (DIS) – Faulty circuit / shorted circuit |
| 17 | Camshaft Position Sensor – Circuit/timing error |
| 18 | Camshaft or Crankshaft – Sensor/circuit/timing error |
| 19 | Crankshaft sensor – Sensor/circuit/timing error |
| 21 | Throttle position sensor – Out of range/Performance |
| 22 | Throttle position sensor – Low Voltage |
| 23 | Intake Air temp sensor – Out of range, low resistance |
| 24 | Vehicle speed sensor – Circuit fault |
| 25 | Intake Air temp sensor – Out of range, high resistance |
| 26 | QDM A ( Quad-driver module ) – Circuit #1 fault |
| 27 | QDM A ( Quad-driver module ) – 2nd gear circuit |
| 28 | QDM A ( Quad-driver module ) – Circuit #2 fault |
| 29 | QDM A ( Quad driver module ) – 4th gear circuit |
| 31 | Wastegate solenoid – Circuit fault |
| 32 | EGR ( Exhaust Gas Recirculation ) – Circuit fault |
| 33 | Manifold Air Pressure Sensor – Signal out of range, high resistance |
| 34 | Manifold Air Pressure Sensor – Signal out of range, low resistance |
| 35 | Idle air control valve / Sensor – Circuit fault |
| 36 | Ignition system – Circuit error/fault |
| 38 | Brake input ( Brake switch sensor ) – Circuit fault |
| 39 | Clutch input ( Clutch sensor ) – Circuit fault |
| 41 | Camshaft sensor – Circuit fault or ignition control – circuit fault/error (depending on the car model) |
| 42 | EST (Electronic spark timing) – Circuit grounded/shorted |
| 43 | Knock sensor / Electronic spark control – Circuit fault error (depending on the car model) |
| 44 | Oxygen O2 sensor – Lean Mixture |
| 45 | Oxygen O 2sensor – Rich Mixture |
| 46 | Pass-key II – Circuit or Power steering pressure switch – circuit fault error (depending on the car model) |
| 47 | PCM data – Circuit error |
| 48 | Misfire (diagnosis) |
| 51 | Calibration error – Mem-cal, ECM, or EPROM failure |
| 52 | Engine oil temperature circuit – Low temperature indicated / circuit error |
| 53 | Battery voltage – Low/high/error or Egr valve solenoid 1 – circuit error (depending on the car model ) |
| 54 | Fuel Pump – Circuit error or Egr valve solenoid 2 – Circuit error (depending on the car model ) |
| 55 | ECM PCM – Circuit error or EGR valve solenoid 3 – Circuit error (depending on the car model ) |
| 56 | Quad-driver module (QDM B) – Circuit error |
| 57 | Boost control – Error / Faulty |
| 58 | Vehicle anti-theft system ( VATS ) – Circuit faulty |
| 61 | AC (Air conditioning), system performance (or degraded oxygen sensor sign) (depending upon the vehicle model). |
| 62 | Engine oil temperature sensor – High temperature indicated |
| 63 | Oxygen O2 sensor right side – Circuit open or MAP (manifold air pressure sensor ) – out of range (depending on the car model ) |
| 64 | Oxygen O2 sensor right side – Lean mixture indicated |
| 65 | Oxygen O2 sensor right side – Rich mixture indicated |
| 66 | A/C (Air conditioning ) pressure sensor – Circuit low pressure |
| 67 | A/C (Air conditioning ) pressure sensor – Circuit or a/c clutch – circuit failure (depending on the car model) |
| 68 | A/C (Air conditioning ) compressor relay – Circuit failure error |
| 69 | A/C (Air conditioning ) clutch – Circuit/pressure high |
| 70 | A/C (Air conditioning ) refrigerant pressure – Circuit high |
| 71 | A/C (Air conditioning ) evaporator temperature sensor – circuit low |
| 72 | Gear selector switch – Circuit error/fault |
| 73 | A/C (Air conditioning) Evaporator temperature – Circuit high |
| 75 | Digital EGR #2 – Solenoid error/faulty |
| 76 | Digital EGR #3 – Solenoid error/faulty |
| 77 | Digital EGR #1 – Solenoid error/faulty |
| 79 | Vehicle speed sensor (SS) – Circuit signal high resistance |
| 80 | Vehicle speed sensor (VSS) – Circuit signal low resistance |
| 81 | Brake input data – Circuit faulty |
| 82 | Ignition control (IC) 3X – Signal error/faulty circuit |
| 85 | Prom – Error/faulty circuit |
| 86 | Analog/digital – Pcm error /faulty circuit |
| 87 | Eprom – Error / faulty circuit |
| 99 | Power management – Error / faulty circuit |
OBD1 Connector Locator
The OBD1 connection is located underneath your steering wheel. Sometimes, the OBD1 connector might have a cover made of black plastic that you will need to take off before you can get access. It is usually black with 12 pins. This connector can be identified easily.
Take a look at the photo above to see how an OBD1 connector appears.
Pinout of OBD1 Connector Wirings
Although the OBD1 connector contains 12 pins (not all) they are utilized in many car models. However, the standard pins such as ground, power and diagnostic are identical in all car models.
Make sure you connect your wires correctly, as if you are not careful, it may damage your vehicle’s electrical system and control units, which can be very expensive.
Here is the OBD1 connector pinout in most cars. Check your manual to see the exact pinout.
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How to Access OBD1 Codes from Home
The easiest way to read without using a diagnostic tool, is to shorten the pin A/pin B circuits. The car will then enter the diagnostic mode and flash the “check engine Light” several times, and we should count the flashes to figure out the diagnostic codes.
How to find the OBD1 codes
- If you need to do any type of electrical work that involves the ignition, make sure to connect your car battery charger. The low voltage could cause many problems with troubleshooting, as well as error codes that are not desired.
- Place a jumper cable between PIN A & PIN B.
- Turn the ignition ON and let the jumper cable rest. Don't start the engine.
- You will see the check engine lamp flash. Keep counting the flashes. There will be a longer pause between the codes if you have several trouble codes and a shorter pause between the trouble codes’ digits. For example, code 16 = 1 flash * Pause * 6 flashes.
- When all trouble codes are outputted, it will flash the code 12 – 1 flash * Pause * 2 flashes.
- Note down the problem codes you received and then check the table below.
- Take out the jumper wires and car battery charger.
OBD1 Code Reader
OBD1 codes readers are available in many sizes and colors to simplify your job. An OBD1 code scanner does not require you to cut the connector and it doesn't count flashes.
This will let you know the issue in plain text. It is a good investment if your vehicle has a lot trouble codes.
There are many code scanners available on the market, all at different prices. Although some scanners have the ability to read OBD1 codes and OBD2 code, these can be very expensive. The Innova 3123 scanner is a great option. There are two options available: GM or Ford vehicles. You can also find the scanner on Amazon if you'd like to have a closer look.
INNOVA 3123 GM OBD1 Code Reader
- You can safely access the onboard computer from anywhere in the world to...
- It works on all domestic General Motors vehicles
- It connects to the vehicle's computer...
- It will not cause any damage to the computer in your vehicle...
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