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Displaying & Reading Trouble Codes

NOTE: This is the only information provided by the manufacturer for reading Diagnostic Trouble Codes for this system.

PRE-CHECK

1. DIAGNOSIS SYSTEM

a. Description
- When troubleshooting OBD II vehicles, the only difference from the usual troubleshooting procedure is that you need to connect the vehicle to 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 Light (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) pre scribed by SAE J2012 are recorded in the ECM memory.
If the malfunction does not reoccur in 3 consecutive trips, the MIL goes off automatically but the DTC remains recorded in the ECM memory.




- To check the DTC, connect the OBD II scan tool or LEXUS hand-held tester to the Data Link Connector 3 (DLC3) of the vehicle. The OBD II scan tool or LEXUS hand-held tester also enables you to erase the DTC and check freeze frame data and various forms of engine data (For operating instructions, see the OBD II scan tool's instruction book.). DTC includes 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 a manufacturer within the prescribed limits.

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

- *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). The 2 trip repeats the same mode twice (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 - P0308) or fuel trim malfunction (DTCs P0171, P0172, P0174 and P0175) or other malfunction (first malfunction only), is detected, as 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 chant, these should be followed.
If no instructions are given, troubleshoot DTCs according to the following priorities.
1. DTC other than fuel trim malfunction (DTCs P0171, P0172, P0174 and P0175), and misfire (DTCs P0300 - P0308).
2. Fuel trim malfunction (DTCs P0171, P0172, P0174 and P0175).
3. Misfire (DTCs P0300 - P0308).







b. Check the DLC3.
The vehicle's ECM uses ISO 9141-2 for communication. The terminal arrangement of the 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 the communication is normal when the tool is connected to another vehicle, inspect the DLC3 on the original vehicle.
- If the communication is still impossible 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.

2. 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 is started, the MIL should go off. If the light 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) or 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, all DTC and freeze frame data recorded in the normal mode will be erased. So before switching modes, always check the DTC and freeze 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 center 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 DTC and freeze 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 DTC.

NOTE:
- When simulating symptoms with an OBD II scan tool (excluding LEXUS hand-held tester) to check the DTC, 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 once. 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 freeze 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 terminal or EFI and ECTS fuses.

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 freeze frame data will be erased.

3. 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.

a. Check the DTC.
1. Initial conditions
- Battery positive voltage 11 V or more
- Throttle valve fully closed
- Transmission in the 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 at the lower center 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 DTC and freeze frame data will be erased.




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

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

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

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

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

b. Clear the DTC.
The following actions will erase the DTCs and freeze frame data.
- Operating the hand-held tester to erase the codes. (See the hand-held tester's instruction book for operating instructions.)
- Disconnecting the battery terminal or EFI and ECTS fuses.

P0100 - P1325:




4. FAIL-SAFE CHART
If any of the codes is recorded, the ECM enters into the fail-safe mode.

5. CHECK FOR INTERMITTENT PROBLEMS
LEXUS hand-held tester only:
By putting the vehicle's ECM in the check mode, the 1 trip detection logic is possible instead of the 2 trip detection logic and sensitivity to detect open circuits is increased. This makes it easier to detect intermittent problems.
1. Clear the DTC.
2. Set the check mode.
3. Perform a simulation test.
4. Check the connector and terminal.
5. Handle the connector.

6. ENGINE OPERATING CONDITION

NOTE: The values given below for "Normal Condition" are representative values, so a vehicle may still be normal even if its value differs from those listed here. So do not solely depend on the "Normal Condition" here when deciding decide whether a part is faulty or not.

Part 1:




Part 2:




a. CARB mandated signals.




b. LEXUS Enhanced Signals.







7. BASIC INSPECTION
When the malfunction code is not confirmed in the DTC check, troubleshooting should be carried out in the order for all possible circuits to be considered as the causes of the problems. In many causes, by carrying out the basic engine check as shown in the flow chart, the location causing the problems can be found quickly and efficiently. Therefore, using of this check is essential in the engine troubleshooting.
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