Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
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HOMESERVICE MANUALSTOYOTA2004TACOMA PRERUNNER V6-3.4L (5VZ-FE)REPAIR AND DIAGNOSISPOWERTRAIN MANAGEMENTTRANSMISSION CONTROL SYSTEMSTESTING AND INSPECTIONSCAN TOOL TESTING AND PROCEDURESDIAGNOSIS (NORMAL MODE)
2004 Toyota Tacoma PreRunner V6-3.4L (5VZ-FE)
Diagnosis (Normal Mode)
2004 Toyota Tacoma PreRunner V6-3.4L (5VZ-FE)SECTION Diagnosis (Normal Mode)
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 lamp remains on, the diagnosis system has detected a malfunction or abnormality in the system.
b. Check the DTC.
NOTE: Hand-held tester only: When the diagnostic system is switched from normal mode to check mode, it erases all DTCs and freeze frame data recorded in normal mode. So before switching modes, always check the DTCs and freeze frame data, and note them down.
1. Prepare an OBD II scan tool (complying with SAEJ1978) or hand-held tester.
2. Connect the OBD II scan tool or hand-held tester to DLC3 at the lower of the instrument panel.
3. Turn the ignition switch ON and turn the OBD II scan tool or hand-held tester switch ON.
4. Use the OBD II scan tool or hand-held tester to check the DTCs and freeze frame data and note them down (For operating instructions, see the OBD II scan tool's instruction book).
5. See Diagnostic Trouble Code Chart to confirm the details of the DTCs.
NOTE: When simulating symptoms with an OBD II scan tool (excluding hand-held tester) to check the DTCs, use normal mode. For codes on the DTCs chart subject to "2 trip detection logic", turn the ignition switch off after the symptoms have been simulated the 1st time. Then repeat the simulation process again. When the program has DTCs, the DTCs are recorded in the ECM.
c. When using the OBD II scan tool or hand-held tester: Clearing the DTCs.
1. Connect the OBD II scan tool or hand-held tester to the DLC3.
2. Turn the ignition switch to the ON position and push the OBD II scan tool or the hand-held tester main switch on.
3. When using hand-held tester:
Select the item "DIAGNOSIS/ENHANCED OBD II/DTC INFO/CLEAR CODES [YES] button".
HINT: When using the OBD II scan tool (complying with SAE J1978) or hand-held tester to erase the codes, the DTCs and freeze frame data will be erased. (See the OBD II scan tool's instruction book for operating instructions.)
d. When not using the OBD II scan tool or hand-held tester: Clearing the DTCs.
Disconnecting the battery terminal or remove the EFI fuse from the engine room J/B for 60 seconds or more. But if you disconnect the battery terminal, you should do the "INITIALIZE" procedure.
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 lamp remains on, the diagnosis system has detected a malfunction or abnormality in the system.
b. Check the DTC.
NOTE: Hand-held tester only: When the diagnostic system is switched from normal mode to check mode, it erases all DTCs and freeze frame data recorded in normal mode. So before switching modes, always check the DTCs and freeze frame data, and note them down.
1. Prepare an OBD II scan tool (complying with SAEJ1978) or hand-held tester.
2. Connect the OBD II scan tool or hand-held tester to DLC3 at the lower of the instrument panel.
3. Turn the ignition switch ON and turn the OBD II scan tool or hand-held tester switch ON.
4. Use the OBD II scan tool or hand-held tester to check the DTCs and freeze frame data and note them down (For operating instructions, see the OBD II scan tool's instruction book).
5. See Diagnostic Trouble Code Chart to confirm the details of the DTCs.
NOTE: When simulating symptoms with an OBD II scan tool (excluding hand-held tester) to check the DTCs, use normal mode. For codes on the DTCs chart subject to "2 trip detection logic", turn the ignition switch off after the symptoms have been simulated the 1st time. Then repeat the simulation process again. When the program has DTCs, the DTCs are recorded in the ECM.
c. When using the OBD II scan tool or hand-held tester: Clearing the DTCs.
1. Connect the OBD II scan tool or hand-held tester to the DLC3.
2. Turn the ignition switch to the ON position and push the OBD II scan tool or the hand-held tester main switch on.
3. When using hand-held tester:
Select the item "DIAGNOSIS/ENHANCED OBD II/DTC INFO/CLEAR CODES [YES] button".
HINT: When using the OBD II scan tool (complying with SAE J1978) or hand-held tester to erase the codes, the DTCs and freeze frame data will be erased. (See the OBD II scan tool's instruction book for operating instructions.)
d. When not using the OBD II scan tool or hand-held tester: Clearing the DTCs.
Disconnecting the battery terminal or remove the EFI fuse from the engine room J/B for 60 seconds or more. But if you disconnect the battery terminal, you should do the "INITIALIZE" procedure.
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When to See a Mechanic
Stop DIY work and contact a certified mechanic immediately if any of the following apply:
- • You smell fuel, burning insulation, or see smoke.
- • Brakes feel soft, pull hard to one side, or make grinding noises.
- • The engine overheats, stalls repeatedly, or misfires under load.
- • You are missing required tools, torque specs, or safe lifting equipment.
- • You are not confident in the next step or safety outcome.