How To Check Obd1 Codes With A Paperclip


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 Although these connectors are outdated, you can still read them with no diagnostic tools.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.

Terminals Odb1

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


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