Question about 2005 Nissan Altima
To RESET the Check Engine light, try this procedure, disconnecting the battery might reset the check engine light on some cars. However, instead of doing so, I'd recommend to bring your car to a dealer or a mechanic for proper diagnostic, and here is why:
- not all cars will clear the code after disconnecting the battery
- often, the problem may be actually covered by the warranty and repaired free of charge by your dealer. For example, if you have the code P0420 - Catalyst System Efficiency Below Threshold it's very possible that your catalytic converter is still covered by the original emission warranty and might be replaced free of charge (would cost you close to $1000 otherwise).
- some problems, if not repaired in time may cause a serious damage and more costly repair.
- the Readiness code will be erased, which may prevent your car from completing an emissions test. (Readiness code is an indication that certain emission control components of your car have been self-tested)
- the radio, if code-protected, may be locked after disconnecting the battery
- the "check engine" light will come back anyway if the problem still exist.
The code itself doesn't tell exactly what component is defective - it only indicates where ... detected that your engine is misfiring, which could damage your catalytic converter.
When the engine is warmed up and running normally the upstream oxygen sensor reading fluctuates and the downstream one is fairly steady. In the case where both readings are fairly steady, a P0420 check engine light code is set.
- Oxygen (O2) sensor not working correctly
- Damaged or leaking exhuast (pipe, manifold, catalytic converter)
- Damaged catalytic converter
To diagnose a P0420 trouble code we begin by checking for exhaust leaks under the vehicle. Then use an oscilliscope to check the waveforms of both upstream and downstream O2 sensors. The front reading should vary, the rear should be steady. Replace as necessary. Check the rear Heated O2 Sensor. Check the catalytic converter, replace if necessary. If necessary, check for wiring and component concerns.
Hope this helps; keep us updated.
Posted on Jan 03, 2011
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Posted on Jan 02, 2017
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