Diagnostic Aids
WARNING: This page is about a different car, the 2003 Lexus ES 300. However, it is still accessible from the selected car via links, so may be relevant.
- When 2 or more codes for misfiring cylinder are recorded repeatedly but no random misfire code is recorded, it indicates misfires were detected and recorded at different times.
- If misfire cannot be reproduced, reason may be because of driving with lack of fuel, improper fuel, fouled spark plug, etc.
- If DTCs besides misfire are recorded simultaneously, perform troubleshooting for them first.
- Read freeze frame data using hand-held tester or OBD-II scan tool, as freeze frame data records engine conditions when a malfunction is detected. When troubleshooting, it is useful to determine whether vehicle was running or stopped, engine was warmed up or not, air-fuel ratio was lean or rich, etc. at time of malfunction.
- Misfiring cylinder identification is disabled at high engine speed and only a general misfire code (P0300) is stored instead of a specific cylinder fault code. When DTC P0300 is stored, erase the DTC after reading freeze frame data. Start engine and perform confirmation driving pattern. See Confirmation Driving Pattern and read value of misfire ratio for each cylinder. Perform repair for high misfire ratio cylinder. After completing repair, confirm no misfire is occurring by performing confirmation driving pattern. See Confirmation Driving Pattern .
- When either of SHORT FT #1, LONG FT #1, SHORT FT #2 or LONG FT #2 in freeze frame data is over range of ±20%, there is a possibility that air-fuel ratio is inclining either to "RICH" (-20 percent or less) or "LEAN" (+20 percent or more). When COOLANT TEMP in freeze frame data is less than 176°F (80°C), there is a possibility of misfire only during warming up engine.
- If the misfire cannot be reproduced, reason may be driving vehicle with lack of fuel, use of improper fuel, a faulty ignition plug, etc.
- Be sure to check value on misfire counter after repair.