Cheat emissions test pass smog P0420 P0430 Catayltic converter
Many people are desperate to keep their cars on the road with limited funds for repairs. In the USA many states have tough pollution laws that require drivers to spend thousands of dollars on emissions repairs or lose the ability to drive that car legally. Of course if you have the cash go ahead and fix your car properly you cheapskate.
If you are mechanically savvy and desperate for some money-saving ideas then read on. The following information is for educational purposes only. You should never tamper with a car without proper training and tools.
Most older cars (pre-1996) that fail for CO need a new oxygen sensor.
Older cars with high NOX reading may have timing set too advanced, a malfunctioning EGR system or an empty catalytic converter. Overheating will also cause a high NOX reading.
P0171 P0174 Fuel system lean. Air leaks (vacuum leaks) and mass air flow sensors. Using a scan tool and some metallic tape you can block off some of the void space on the inlet side of the mass air flow sensor to increase the sensors air volume reading. With a little practice you can get the fuel trim numbers just right and eliminate these fault codes.
P0401 Toyota: If all the EGR components test okay replace the vacuum switching valve.
P0128 Honda Civic Radiator temperature sensor.
P0420 P0430 catalytic converter. Pack rear oxygen sensors (behind converter) with RTV, silicone gasket maker. Clear codes and drive on the highway. If this makes the car run funny then replace the rear sensors after passing the emissions test. Never do this to a front oxygen sensor before the converter. Another method on cars with two rear oxygen sensors is to connect the two rear signal wires together. The averaging of the voltage can sometimes make it pass. Wiring diagram needed.
Some faults do not need to be repaired like evap problems in order to pass the test. A mechanic can perform the drive cycle with scan tool and test the car at the right moment before the fault appears.
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