- 1). Place your key into the 2004 Chevrolet Silverado's ignition and start the engine. What till all the systems are up and running and look at the instrument cluster behind the steering wheel. Is the check engine light on? If so, there are active trouble codes within the OBD-II system. If not, there still may be codes stored in the computer that the scanner will read. Trouble codes are often recorded malfunctions. Pending codes are malfunctions that have occurred, but not with the frequency the OBD-II system requires for "trouble" status.
- 2). Turn the 2004 Chevrolet Silverado's key to "Off." Connect your OBD-II scanner's diagnostic cable to the Silverado's Data Link Connection. You will find the DLC port right above the parking break, to the left of the steering column.
- 3). Power on your OBD-II scanner. You may not have to do that, depending on the hardware you own. Some diagnostic scanners are preset to switch themselves on once they detect a live data stream from a vehicle's computer.
- 4). Insert the key in the ignition to the "On" position and activate the Silverado's electrical system. This should wake up the OBD-II system. If it doesn't, then you own a scanner that requires the engine started. If that is the case, start the Silverado's engine.
- 5). Look at the scanner's display. If the scanner hasn't automatically fetched the codes out from the Silverado, then your scanner requires you to issue a retrieval command. Operations, layout, buttons, and the entire system varies by a scanner's brand and model. For the precise way to do this, consult your scanner's handbook.
- 6). Scroll through the codes on the scanner. The codes will be differentiated on the display. You will be looking for "P" (powertrain) codes. Your scanner will also differentiate between "trouble" and "pending." On a sheet of paper, write down all the trouble codes first. Then, write down all the pending codes beneath.
- 7). Turn the key in the Silverado's ignition to "Off." Remove the key and remove the OBD-II scanner's diagnostic cable from the DLC port.
- 8). Consult your scanner's handbook for generic OBD-II code meanings. There should be an appendix towards the rear of the handbook that contains a list of these meanings. Copy them out ont the list you started in Step 6. All General Motors vehicles, Chevrolet included, use additional OBD-II codes that you may have to look up. Neither the scanner's handbook nor the Silverado's owner's manual will contain these codes. The cheapest option includes looking them up on the internet (See Resources), and then adding the coding definitions to your list.
- 9). Return to your Silverado and open the engine compartment. Follow the order of your list, and investigate the portions of the engine that correspond with the codes you have retrieved.
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