Are you a GM owner with a vehicle manufactured between 1980 and 1995? There is a possibility that your car contains an OBD1 connector (ALDL).
This connector works with Pontiac and Chevrolet as well as Oldsmobile and Cadillac. You can use the OBD1 connector to read your trouble codes from home without any diagnostic tools.
If you own a GM car from 1980-1995, there is a good chance that you have an OBD1 connector. OBD1 connectors are available for Pontiac and Oldsmobile cars. Although these connectors are outdated, you can still read them with no diagnostic tools.
These connector codes are easily readable by many diagnostic tools. However, they may not be necessary to be read. To check ODB1 codes, you only need a piece of paper.
How to Check ODB1 codes using a paperclip
With a paperclip, you can quickly check ODB1 codes.
These are the steps to verify ODB1 codes with a paperclip.
1. Find a Paperclip
Many people keep paperclips around their homes. You can use a paperclip for bending or shaping it to fit your diagnosis box.
2. Insert into Test Terminal
Turn off your engine. Attach the paperclip to both terminals, A & B. This is where jumper wires are usually placed.
A = Ground
B = Diagnosis terminal
Lock the key and turn it counterclockwise.
After that, the system will enter diagnostic mode.
3. Check the codes
After the vehicle enters diagnostic mode, it’s time to verify the codes. The vehicle’s computer will show a Code 12each time in this mode.
Flash the “CHECK ENGINE,” the “SERVICE ENGINE SOON,” or the “MALFUNCTIONLAMP” or light to do this.
What’s a Code 12?
Code 12 combines a flash followed by a short pause, then two flashes in rapid succession for simple identification. After Code 12 is displayed, it’s time to look for trouble ODB1 code. Each code will be shown three times and then again.
Write down the codes to resolve the issue with your vehicle.
These Are The ODB1 Trouble Codes
12 – System Okay
13 – Circuit Open No Activity
14 – Coolant Temperature Sensor (high resistance or shorted Circuit)
15 -Low water temperature sensor circuit, or
16 – Fault in the Circuit caused by the direct ignition system (DIS).
17 – Camshaft position sensor fault
18 – Crankshaft or camshaft sensor error
19 – Crankshaft sensor circuit fault
21 TPS sensor out of range
22 Low voltage TPS sensor signal
23 Intake temperature sensor out of range, low
24 Vehicle speed (VSS), sensor circuit fault
25 Air temp sensor
26 – Quad-driver module (QDM) circuit #1 fault
27 Quad-driver module 2nd gear circuit
28 – Quad-driver module circuit #2 fault
29 – Quad driver module 4th gear circuit
31 – Camshaft position sensor fault
32 – EGR circuit fault
33 Map sensor signal out-of-range, high
34 Map sensor signal out-of-range, low
35 – Faulty idle air control sensor circuit
36 – Ignition system circuit error
38 Brake input circuit fault
39 Clutch input (Clutch Sensor)
41 – Camshaft sensor circuit fault OR ignition control circuit fault
42 Electronic spark timing (EST), Circuit grounded
43 Knock sensor, or electronic ignition control circuit fault
44- Oxygen sensor exhaust
45 – Oxygen sensor rich exhaust
46 Pass-key II circuit or power steering pressure switch circuit fault
47 – PCM data circuit
48 – Misfire diagnosis
51 Calibration error ECM or EPROM fail
52 Temperature circuit for engine oil, low temperatures indicated
53 Voltage error, EGR or pass-key II circuit
54 EGR system failure, fuel pump circuit low-voltage
55 Conversion error, or PCM not grounded, lean fuel or founded reference voltage
56 – Quad-driver module #2 circuit
57 – Boost control problem
58 Vehicle anti-theft fuel enable Circuit
61 AC performance or degraded oxygen sign
HTML2_ 62 High engine oil temperature indicated
HTML63 Oxygen sensor right-side Circuit open or map sensor out range
64- Oxygen sensor right side exhaust indicated
65 – Oxygen sensor right side rich mixture indicated
HTML66 Low-Pressure AC Pressure Sensor Circuit
67 AC pressure sensor circuit or a/c circuit failure
68 – AC compressor relay circuit failure
69 High head pressure in AC clutch circuit
70 – AC refrigerant pressure circuit high
71 Low-temperature AC evaporator temperature sensor circuit
72- Circuit for the gear selector switch
– Circuit for high AC evaporator temperature
75 – Digital EGR #1 solenoid error
76 – Digital EGR #2 solenoid error
77 – Digital EGR #3 solenoid error
79 Motor speed sensor (VSS signal high)
80 Motor speed sensor (VSS signal low
81 Brake input circuit fault
82 Ignition control (IC), 3X signal error
85 – Prom error
86 – Analog/digital PCM error
87- Eprom Error
99 Power management
4. Reset the Codes
Once you have resolved the problem and read all the codes, resetting them, it is time to restart your ECU. Take care not to pull the battery’s negative terminal. Drive the car for 75+ miles around the area or take the highway for 150+ to resolve the problem.
Now, use the paperclip method to check if your code is still there.
OBD1 Connector Locator
The OBD1 connector is located underneath your steering wheels, below the dash. You may need to take off the black plastic cover that covers the connector before you can access it. It is usually black with 12 pins. This connector is easy to identify.
Pinout of OBD1 Connector Wirings
There are 12 pins in the OBD1 connector, but not all models will be used. However, you can use standard pins such as ground, power, and a diagnostic pin in all car models.
You must ensure that you correctly connect the wires; otherwise, it could damage your vehicle’s control units and electrical system, leading to costly repairs.
This version is the OBD1 connector pinout in most cars. Check your manual to see the exact pinout.
Ground = A
B = Diagnosis Terminal
C = A.I.R
D = Service Engine Soon Light
E = Serial Data
F = T.C.C
G = Fuel pump
H = Brake speed input
J = None
K = None
L = None
M = Serial Data
Still Want An ODB1 Scanner?
OBD1 code readers are available in many sizes to simplify your job. An OBD1 code scanner does not require you to shorten the connector, and it counts the flashes, letting you know the problem clearly on your device. It is an excellent investment if you have a lot of trouble codes from older vehicles.
Many code scanners ply the market at different prices. While some scanners can read both OBD1 and OBD2 codes, they can be pretty 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. If you are determined to buy one, here are the top ODB1 scanners:
Innova 3123 GM OBD1 Scanner
Innova 3120 OBD2/OBD1 Code Reader
Foxwell NT510 OBD2/OBD1 Multisystem Scan Tool
Innova 3145 Ford OBD1 Code Reader