Inspection Procedure

HINT:

• If any DTCs other than misfire DTCs are output, troubleshoot those DTCs first.

• Read freeze frame data using the intelligent tester. The ECM records vehicle and driving condition information as freeze frame data the moment a DTC is stored. When troubleshooting, freeze frame data can help determine if the vehicle was moving or stationary, if the engine was warmed up or not, if the air-fuel ratio was lean or rich, and other data from the time the malfunction occurred.

• If the misfire does not recur when the vehicle is brought to the workshop, reproduce the conditions stored in the freeze frame data.

• If the misfire still cannot be reproduced even though the conditions stored in the freeze frame data have been duplicated, one of the following factors is considered to be a possible cause of the problem:

(a)The fuel level is low.

(b)Improper fuel is used.

(c)The spark plugs are dirty.

(d)The problem is complex due to multiple factors.

• After finishing repairs, check that no misfires occur in each cylinder (CYL #1, #2, #3 and #4).

• Be sure to confirm that no misfiring cylinder DTCs are set again by conducting the confirmation driving pattern, after the repairs.

• For 6 and 8 cylinder engines, the ECM intentionally does not set the specific misfiring cylinder DTCs at a high engine RPM. If misfires only occur during high engine RPM driving, only DTC P0300 is set.

In the event of DTC P0300 being present, perform the following operations:

(b)Start the engine and conduct the confirmation driving pattern.

(c) Read the misfiring rates of each cylinder or DTC(s) using the tester.

(d)Repair the cylinder(s) that has a high misfiring rate or is indicated by the DTC.

(e)After finishing repairs, conduct the confirmation driving pattern again, in order to verify that DTC P0300 is not set.

• When either SHORT FT #1 or LONG FT #1 in the freeze frame data is outside the range of +-20 %, the air-fuel ratio may be rich (-20 % or less) or lean (+20 % or more).

• When the COOLANT TEMP in the freeze frame data is less than 75°C (167°F), the misfires occurred only while warming up the engine.

Do It Yourself Car Diagnosis

Do It Yourself Car Diagnosis

Don't pay hundreds of dollars to find out what is wrong with your car. This book is dedicated to helping the do it yourself home and independent technician understand and use OBD-II technology to diagnose and repair their own vehicles.

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