: Pcm 0420 Code???



dexec
10-18-04, 06:01 PM
I have a 98 SLS with the PCM 0420 CODE. The plugs and wires have been changed along with BAnk 2 Sensor 1-02 Sensor and another 02 Sensor. Fuel Pressure Regulator has also been changed. I know the PCM 0420 is the Code for Catalyst System Low Efficiency. What exactly does that mean??? Do I need to change the Catalytic Converter??? Is there a vacuum leak?? Car runs pretty well, but hesitates under hard acceleration!!! Code is able to be cleared for a day or so and comes right back. Just want to know where the problem might be coming from????

cadtech
10-18-04, 09:04 PM
The only thing that I have seen cause this code is the cat. converter. The good news it is covered for 8 years or 80k miles unless damaged.

scorpioUSA
07-24-06, 07:20 AM
The only thing that I have seen cause this code is the cat. converter. The good news it is covered for 8 years or 80k miles unless damaged.

It could also be the mass air flow sensor.

FrankT
07-24-06, 06:30 PM
It could also be the mass air flow sensor.

Please explain to me how a mass air flow sensor can set this DTC?

The Mass Air Flow Sensor dtcs are as follows:
P0101 ( Mass Air Flow performance)
P0102 ( Mass Air Flow circuit Low Frequency)
P0103 ( Mass Air Flow circuit High Frequency)

P0420 is an Catalyst System Low Efficiency algorithm.

The PCM determines the performance of the catalytic converter by calculating the oxygen storage capacity of the Catalyst.

The only thing I can see setting the DTC is an exhaust leak before the cat or a degraded catalytic converter.

Now for the hesitation, I can possibly see as a contaminated Mass Air Flow Sensor

bone-daddy
07-25-06, 02:07 AM
i think your car wants you to get high.