The light is on????

2001 MITSUBISHI MONTERO
120,000 MILES • 6 CYL • 2WD • AUTOMATIC
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BAMAFAN75
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  • 1 POST
I have a 2001 mitsubishi Montero Sport with the check engine light on. The following trouble codes were noted P0300 and P0421. The vehicle runs fine and just turned 120,000 miles. What is the solution?
Jan 5, 2011 at 3:41 PM
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ERNEST CLARK
  • ✓Experienced Mechanic
  • 1,730 POSTS
P0300= Random Misfire. These are the possible causes: (Remember to test before replacing)

Ignition system related part(s) failed.
Poor crankshaft position sensor.
Incorrect air/fuel ratio.
Low compression pressure.
Skipping of timing belt teeth.
EGR system and EGR valve failed.
PCM failed.

P0421= Warmup Catalyst Efficiency Below Threshold - bank 1 (Right side of engine)

The signal from the rear heated oxygen sensor differs from the front heated oxygen sensor. That is because the catalytic converter purifies exhaust gas. When the catalytic converter has deteriorated and/or the rear 02 sensor is bad, the signal from the front heated oxygen sensor becomes similar to the rear heated oxygen sensor.
The PCM compares the output of the front and rear heated oxygen sensor signals.

Feb 24, 2011 at 5:36 AM
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