GM Powertrains - Auto Repair Codes

Scan Tool for Codes and Live Data for your GM Engine from $199 USD

The information below may apply to GM Sonoma, Van and many other models

Step 4

GM EFI Code Reading

Connector Diagram

Note: You may need the OBD2 / EOBD or UniPlug vehicle specific software.
Click here for more info.

Auto Repair Manual - How to read codes (No Special Tools Needed)

1 If possible run the engine, to bring it and the oxygen sensor up to operating temperature, then switch the engine OFF.

2 Connect the terminals with a your own wire link, (Click here for details) , as shown in the diagram to your left.

3 Turn the ignition ON, the Check Engine Light (CEL) should be flashing.

4 Read codes as described in the Code Format Description below.

5 Press the continue button to enter the code numbers and get the code description.

Code Format Diagram

Code Format Description

• Each code consists of two groups.

• The first group of flashes indicate the 'tens' digits.

• The second group of flashes indicate the 'ones' digits.

• A short pause separates 'tens' and 'ones' digits.

• A long pause separates each trouble code.

• Code Format Diagram shows code No. 21.

To move to the next screen click on the Continue button

 Continue > 

Note on Example Model(s): GM Sonoma, Van
The example model(s) shown, GM Sonoma, Van for this auto repair service are only an indication to help you. There may be many other models that apply to this connector. Click above link to see the complete vehicle coverage list.