Displaying & Reading Trouble Codes

NOTE: This is the only information provided by the manufacturer for reading diagnostic trouble codes for this system.

DIAGNOSIS SYSTEM

Description
When troubleshooting OBD II vehicles, the only difference from the usual troubleshooting procedure is that you connect to the vehicle the OBD II scan tool complying with SAE J1978 or LEXUS hand-held tester, and read off various data output from the vehicle's ECM





OBD II regulations require that the vehicle's on-board computer lights up the Malfunction Indicator Lamp (MIL) on the instrument panel when the computer detects a malfunction in the emission control system/components or in the powertrain control components which affect vehicle emissions, or a malfunction in the computer. In addition to the MIL lighting up when a malfunction is detected, the applicable Diagnostic Trouble Codes (DTCs) prescribed by SAE J2012 are recorded in the ECM memory.

If the malfunction does not occur in 3 trips, the MIL goes off automatically but the DTCs remain recorded in the ECM memory.





To check the DTCs, connect the OBD II scan tool or LEXUS hand-held tester to the Data Link Connector 3 (DLC3) on the vehicle. The OBD II scan tool or LEXUS hand-held tester also enables you to erase the DTCs and check freezed frame data and various forms of engine data (For operating instructions, see the OBD II scan tool's instruction book.). DTCs include SAE controlled codes and manufacturer controlled codes. SAE controlled codes must be set as prescribed by the SAE, while manufacturer controlled codes can be set freely by the manufacturer within the prescribed limits (See DTC chart).Diagnostic Trouble Code Descriptions

The diagnosis system operates in the normal mode during normal vehicle use. It also has a check mode for technicians to simulate malfunction symptoms and troubleshoot. Most DTCs use 2 trip detection logic* to prevent erroneous detection, and ensure thorough malfunction detection. By switching the ECM to check mode when troubleshooting, the technician can cause the MIL to light up for a malfunction that is only detected once or momentarily. (LEXUS hand-held tester only)

* 2 trip detection logic:
When a malfunction is first detected, the malfunction is temporarily stored in the ECM memory (1st trip).

If the same malfunction is detected again during the second drive test, this second detection causes the MIL to light up. (2nd trip) (However, the ignition switch must be turned OFF between the 1st trip and 2nd trip.)

Freeze frame data:
Freeze frame data records the engine condition when a misfire (DTCs P0300-P0306) or fuel trim malfunction (DTCs P0171 and P0172) or other malfunction (first malfunction only), is detected.

Because freeze frame data records the engine conditions (fuel system, calculated load, engine coolant temperature, fuel trim, engine speed, vehicle speed, etc.) when the malfunction is detected. When troubleshooting, it is useful for determining whether the vehicle was running or stopped, the engine was warmed up or not, the air-fuel ratio was lean or rich, etc. at the time of the malfunction.

Priorities for troubleshooting:
If troubleshooting priorities for multiple DTCs are given in the applicable DTC chart, these should be followed.

If no instructions are given, troubleshoot DTCs according to the following priorities.

1. DTCs other than fuel trim malfunction (DTCs P0171 and P0172) and misfire (DTCs P0300 - P0306).
2. Fuel trim malfunction (DTCs P0171 and P0172).
3. Misfire (DTCs P0300 - P0306).








Check the DLC3.
The vehicle's ECM uses the ISO 9141-2 communication protocol. The terminal arrangement of DLC3 complies with SAE J1962 and matches the ISO 9141-2 format.

HINT: If your display shows UNABLE TO CONNECT TO VEHICLE when you have connected the cable of the OBD II scan tool or LEXUS hand-held tester to the DLC3, turned the ignition switch ON and operated the scan tool, there is a problem on the vehicle side or tool side.
If communication is normal when the tool is connected to another vehicle, inspect the DLC3 on the original vehicle.
If communication is still not possible when the tool is connected to another vehicle, the problem is probably in the tool itself, so consult the Service Department listed in the tool's instruction manual.


INSPECT DIAGNOSIS (Normal Mode)





A. Check the MIL.
1. The MIL comes on when the ignition switch is turned ON and the engine is not running.

HINT: If the MIL does not light up, troubleshoot the combination meter.

2. When the engine started, the MIL should go off. If the lamp remains on, the diagnosis system has detected a malfunction or abnormality in the system.

B. Check the DTC.

NOTE: If there is no DTC in the normal mode, check the 1st trip DTC using Continuous Test Results function (Mode 7 for SAE J1979) on the OBD II scan tool or LEXUS hand-held tester.
LEXUS hand-held tester only:
When the diagnosis system is switched from the normal mode to the check mode, it erases all DTCs and freezed frame data recorded in the normal mode. So before switching modes, always check the DTCs and freezed frame data, and note them down.

1. Prepare the OBD II scan tool (complying with SAE J1978) or LEXUS hand-held tester.
2. Connect the OBD II scan tool or LEXUS hand-held tester to the DLC3 at the lower left of the instrument panel.
3. Turn the ignition switch ON and push the OBD II scan tool or LEXUS hand-held tester switch ON.
4. Use the OBD II scan tool or LEXUS hand-held tester to check the DTCs and freezed frame data and note them down (For operating instructions, see the OBD II scan tool's instruction book.).

If there is no DTC in the normal mode, check the 1st trip DTC using Continuous Test Results function (Mode 7 for SAE J1979) on the OBD II scan tool or LEXUS hand-held tester.

5. See TROUBLE CODE DESCRIPTIONS to confirm the details of the DTCs.Diagnostic Trouble Code Descriptions

NOTE: When simulating symptoms with an OBD II scan tool (excluding LEXUS hand-held tester) to check the DTCs, use the normal mode. For code on the DTC chart subject to "2 trip detection logic", perform the following either action.
Turn the ignition switch OFF after the symptom is simulated the first time. Then repeat the simulation process again. When the problem has been simulated twice, the MIL lights up and the DTCs are recorded in the ECM.
Check the 1st trip DTC using Mode 7 (Continuous Test Results) for SAE J1979.

C. Clear the DTC.
The DTCs and freezed frame data will be erased by either action.

- Operating the OBD II scan tool (complying with SAE J1978) or LEXUS hand-held tester to erase the codes. (See the OBD II scan tool's instruction book for operating instructions.)
- Disconnecting the battery terminals or EFI and ECTS fuses.

NOTE: 0mIf the LEXUS hand-held tester switches the ECM from the normal mode to the check mode or vice-versa, or if the ignition switch is turned from ON to ACC or OFF during the check mode, the DTCs and freezed frame data will be erased.

INSPECT DIAGNOSIS (Check Mode)

HINT: LEXUS hand-held tester only:
Compared to the normal mode, the check mode has an increased sensitivity to detect malfunctions.
Furthermore, the same diagnostic items which are detected in the normal mode can also be detected in the check mode.

Check the DTC.
1. Initial conditions
- Battery positive voltage 11 V or more
- Throttle valve fully closed
- Transmission in P or N position
- A/C switched OFF

2. Turn the ignition switch OFF.
3. Prepare the LEXUS hand-held tester.
4. Connect the LEXUS hand-held tester to the DLC3 in the fuse box at the lower left of the instrument panel.
5. Turn the ignition switch ON and push the LEXUS hand-held tester switch ON.





6. Switch the LEXUS hand-held tester from the normal mode to the check mode (Check that the MIL flashes.).

NOTE: If the LEXUS hand-held tester switches the ECM from the normal mode to the check mode or vice-versa, or if the ignition switch is turned from ON to ACC or OFF during the check mode, the DTCs and freezed frame data will be erased.

7. Start the engine (The MIL goes out after the engine start.).
8. Simulate the conditions of the malfunction described by the customer.

NOTE: Leave the ignition switch ON until you have checked the DTCs, etc.

9. After simulating the malfunction conditions, use the LEXUS hand-held tester diagnosis selector to check the DTCs and freezed frame data, etc.

HINT: Take care not to turn the ignition switch OFF. Turning the ignition switch OFF switches the diagnosis system from check mode to normal mode. so all DTCs, etc. are erased.

10. After checking the DTC, inspect the applicable circuit.