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Your vehicle's Instrument panel has several indicator lights, such as the Check Engine, Service Engine Soon, ABS, Shift to D2 and Temperature indicator lights. These lights do more than tell you to check for engine, brake, or other component malfunctions. They can also transmit the service codes in the computer memory by blinking ON and OFF.

• All codes are two digits.
• Each code is transmitted three times before the next code is sent.
• Code sets will begin with Code 12 (System Pass) even if fault codes are present.
• The codes will continue to be sent as long as the ignition is on and the Code Reader is connected.
• Count blinks to get the service codes:

Code 12

Note: Code 12 is not a fault code. Code 12 indicates the computer's self-diagnostic system is functioning properly (System Pass). If code 12 is the only code which displays when you perform the diagnostic test, this means there are no fault codes stored in the vehicle's computer.

Code 22

Important: Any code that ends in zero (0) is transmitted as follows: For example, Code 30.

Example 1:

2 blinks, short pause, 4 blinks, long pause, 2 blinks, short pause, 4 blinks, long pause....and just keeps repeating this cycle, then you only have one code (Code 24).

Example 2:

2 blinks, short pause, 4 blinks, medium pause, 3 blinks, short pause, 1 blink, long pause, 2 blinks, short pause, 4 blinks, medium pause, 3 blinks, short pause, 1 blink, long pause... and just keeps repeating this cycle, then you have two codes (Code 24 and Code 31).

There is a short pause between digits, a medium pause between different codes, and a long pause at the end of all the codes, before the loop starts over again.

Short Pause = 1 second

Medium Pause = 2 seconds

Long Pause = 4 seconds

Using the OBD1 GM Code Reader to Count the Blinks for Codes

Using the OBD1 Ford Code Reader to Count the Blinks for Codes

Click HERE to get to our Diagnostic Code Library for code descriptions.