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Originally Posted by Xrider212
What would the most common cause of those codes be?
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P0171 FUEL INJECTION SYSTEM FUNCTION
Malfunction is detected when fuel injection system does not operate properly, the amount of mixture ratio compensation is too large. (The mixture ratio is too lean.)
POSSIBLE CAUSE
Intake air leaks
Heated oxygen sensor 1
Injectors
Exhaust gas leaks
Incorrect fuel pressure
Lack of fuel
Mass air flow sensor
PCV system (Loose or disconnected rubber tube)
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Diagnostic begins on page
1427 of section EC of the factory service manual.
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P0300 NO.6-1 CYLINDER MISFIRE, MULTIPLE CYLINDER MISFIRE
When a misfire occurs, engine speed will fluctuate. If the engine speed fluctuates enough to cause the CKP sensor signal to vary, ECM can determine that a misfire is occurring.
The misfire detection logic consists of the following two conditions.
1. One Trip Detection Logic (Three Way Catalyst Damage) On the first trip that a misfire condition occurs that can damage the three way catalyst (TWC) due to overheating, the MIL will blink.
When a misfire condition occurs, the ECM monitors the CKP sensor signal every 200 engine revolutions for a change. When the misfire condition decreases to a level that will not damage the TWC, the MIL will turn off. If another misfire condition occurs that can damage the TWC on a second trip, the MIL will blink. When the misfire condition decreases to a level that will not damage the TWC, the MIL will remain on. If another misfire condition occurs that can damage the TWC, the MIL will begin to blink again.
2. Two Trip Detection Logic (Exhaust quality deterioration)
For misfire conditions that will not damage the TWC (but will affect vehicle emissions), the MIL will only light when the misfire is detected on a second trip. During this condition, the ECM monitors the CKP sensor signal every 1,000 engine revolutions.
A misfire malfunction can be detected on any one cylinder or on multiple cylinders. Malfunction is detected when multiple cylinders misfire, No. 1 cylinder misfires, No. 2 cylinder misfires, No. 3 cylinder misfires, No. 4 cylinder misfires, No. 5 cylinder misfires and No. 6 cylinder misfires.
POSSIBLE CAUSE
Improper spark plug
Insufficient compression
Incorrect fuel pressure
The injector circuit is open or shorted
Injectors
Intake air leak
The ignition secondary circuit is open or shorted
Lack of fuel
Drive plate or flywheel
Heated oxygen sensor 1
Incorrect distributor rotor
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Diagnostic begins on page
1462 of section EC of the factory service manual.
Notice that some of the possible causes for both codes are the same so one issue could be causing both codes.
Do yourself a favor and run through the diagnostic procedure and find the cause of the codes rather than replacing a bunch of parts and guessing what is the source of the problem.
Linear Mode
