The ignition module when the ignition is in the 'ON' position, it illuminates the CheckĮngine Lamp (CEL), but does not log this code as it would other codes.Ĭode 12 is used on most systems when in the Diagnostic mode (ALDL Terminal B grounded, When the ECM detects no ignition reference pulses from Trouble Code 12 is a special-case code that is not logged into the ECM's Non-Volatile The following chart gives Code # and Description of the problemĬlick on Malfunction Description to get more detailed information.ġ2 ERROR CODE DIAGNOSTIC SYSTEM FUNCTIONING CORRECTLYġ4 COOLANT TEMPERATURE SENSOR (CTS) CIRCUIT (HIGH TEMP)ġ5 COOLANT TEMPERATURE SENSOR (CTS) CIRCUIT (LOW TEMP)Ģ1 THROTTLE POSITION SENSOR (TPS) CIRCUIT (HIGH)Ģ2 THROTTLE POSITION SENSOR (TPS) CIRCUIT (LOW)Ģ3 MANIFOLD AIR TEMP (MAT) or INTAKE AIR TEMP (IAT) CIRCUIT (LOW TEMP)Ģ5 MANIFOLD AIR TEMP (MAT) or INTAKE AIR TEMP (IAT) CIRCUIT (HIGH TEMP)Ģ6 QUAD-DRIVER (QDM) ERROR (if applicable)ģ2 EXHAUST GAS RECIRCULATION (EGR) CIRCUITģ3 MANIFOLD ABSOLUTE PRESSURE (MAP) SENSOR (VOLTAGE HIGH-LOW VACUUM)ģ4 MANIFOLD ABSOLUTE PRESSURE (MAP) SENSOR (VOLTAGE LOW-HIGH VACUUM)Ĥ1 CYLINDER SELECT ERROR (FAULTY OR INCORRECT MEM-CAL)Ĥ3 ELECTRONIC SPARK CONTROL (ESC) CIRCUITĥ1 MEM-CAL ERROR (FAULTY OR INCORRECT MEM-CAL) This will cause the ECM to reset clearing all Codes, and the ECM will now need to re-learn driving parameters. Power to the ECM must be disconnected for at least thirty (30) seconds. Depending on the car, you can disconnect an inline "pigtail" fuse at the positive battery terminal, or remove the ECM fuse in the fuse block. To clear codes, ensure that the ignition is "OFF".To quit scanning for codes, simply shut the ignition "OFF" and remove the jumper.If more than one code was stored, they will be output from lowest to highest, with each one being displayed three times.Įxample: An error Code 25 will be: 12,12,12,25,25,25,12,12,12, etc.įigure 1: Example of "Service Engine Soon" light flashing Code 12 continuously. Following Code 12, the other trouble codes will be output if present, or Code 12 will be output continuously if no other codes are stored.
Code 12 means the diagnostic system is operating properly.
This would be the following flash sequence: "flash, pause, flash-flash, long pause, flash, pause, flash-flash, long pause, flash, pause, flash-flash" (See Figure 1).
They are essentially expensive jumper wires. NOTE: The cheap $25-30 "scan tool" and the $5 "scan key" that you find at many auto parts stores are NOT actual scan tools. We will also utilize this connector for our "NON-SCAN" method. Regardless of the method used, the secret to communicating with the car's computer is through the ALDL connector (Assembly Line Diagnostic Link). The other method is to perform a "NON-SCAN" diagnostic circuit check by having the "Service Engine Soon" light blink out the codes stored in the ECM. The drawbacks to the scan tool method is that a scan tool costs several thousands of dollars.
#Gm obd1 diagnostic trouble codes full
In full detail, such as the sensor voltage detected and what it should be. The more expensive scan tools also display the details behind the trouble code A scan tool displays trouble codes numerically on a LCD display or computer terminal. The best and easiest way is to purchase a "scan tool". You can read these trouble codes in several different ways. What you need to do first is find out what trouble codes are presently stored in the ECM. If there is an engine malfunction caused or detected by any one of the many sensors connected to the ECM, a trouble code will be stored in NVM, or Non-Volatile Memory. The ECM is constantly controlling, adjusting, and monitoring engine conditions. This computer is called the ECM, or "Electronic Control Module". In every GM W-Body car, there is a computer that controls virtually all aspects of the engine's operation. What do you do when this dreaded light turns on? DO NOT LOAD THIS PAGE DIRECTLY, use GM W-Body ECM Trouble Codes
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