Toyota RAV4 > Emissions and engine control systems > On-Board Diagnostic (OBD) system and Diagnostic Trouble Codes (DTCs)

On-Board Diagnostic (OBD) system and Diagnostic Trouble Codes (DTCs)

OBD system general description

1. All models are equipped with the second generation OBD-II system. This system consists of an on-board computer known as the Powertrain Control Module (PCM), and information sensors, which monitor various functions of the engine and send data to the PCM. This system incorporates a series of diagnostic monitors that detect and identify fuel injection and emissions control systems faults and store the information in the computer memory. This updated system also tests sensors and output actuators, diagnoses drive cycles, freezes data and clears codes. This powerful diagnostic computer must be accessed using the new OBD-II scan tool and 16 pin Data Link Connector (DLC) located under the driver’s dash area.

2. The PCM is the «brain» of the electronically controlled fuel and emissions system. It receives data from a number of sensors and other electronic components (switches, relays, etc.). Based on the information it receives, the PCM generates output signals to control various relays, solenoids (i.e., fuel injectors) and other actuators. The PCM is specifically calibrated to optimize the emissions, fuel economy and drivability of the vehicle.

3. It isn’t a good idea to attempt diagnosis or replacement of the PCM or emission control components at home while the vehicle is under warranty. Because of a Federally mandated warranty which covers the emissions system components and because any owner-induced damage to the PCM, the sensors and/or the control devices may void this warranty, take the vehicle to a dealer service department if the PCM or a system component malfunctions.

Scan tool information

4. Because extracting the Diagnostic Trouble Codes (DTCs) from an engine management system is now the first step in troubleshooting many computer-controlled systems and components, a code reader, at the very least, will be required (see illustration). More powerful scan tools can also perform many of the diagnostics once associated with expensive factory scan tools (see illustration). If you’re planning to obtain a generic scan tool for your vehicle, make sure that it’s compatible with OBD-II systems. If you don’t plan to purchase a code reader or scan tool and don’t have access to one, you can have the codes extracted by a dealer service department or an independent repair shop.

i. 4a Simple code readers are an economical way to extract trouble codes when the CHECK ENGINE light comes on

i. 4b Hand-held scan tools like these can extract computer codes and also perform diagnostics

Note: Some auto parts stores even provide this service free of charge

Accessing the DTCs

5. The Diagnostic Trouble Codes (DTCs) can only be accessed with a code reader or scan tool. Professional scan tools are expensive, but relatively inexpensive generic code readers or scan tools (see illustrations 4a and 4b) are available at most auto parts stores. Simply plug the connector of the scan tool into the diagnostic connector (see illustration). Then follow the instructions included with the scan tool to extract the DTCs.

i. 5 Connect the scan tool to the Data Link Connector (DLC) located under the left side of the dash

Toyota RAV4 Emissions and engine control systems | On-Board Diagnostic (OBD) system and Diagnostic Trouble Codes (DTCs)

6. Once you have outputted all of the stored DTCs, look them up on the accompanying DTC chart.

7. After troubleshooting the source of each DTC, make any necessary repairs or replace the defective component(s).

Clearing the DTCs

8. Clear the DTCs with the code reader or scan tool in accordance with the instructions provided by the tool’s manufacturer.

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