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Joined: Jun 2000
Posts: 140
CEG\'er
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OP
CEG\'er
Joined: Jun 2000
Posts: 140 |
My CEL came on again and I had it checked out. I'm getting code 0420, Catalyst System Efficiency below Limit - Bank No 1, but the mechanic said it is most likely being caused from the downstream O2 sensor.
They did a test with the engine running and found that there was no signal coming from Bank 1 sensor 2. The mechanic said this is strange because usually the sensor will just be out of spec. He said it would be rare for the sensor to fail in this way (no signal) and that more likely it was a problem with the O2 sensor wiring.
What do you guys think? Or is it really the cat?
2002 BMW M5
Carbon Black on Black
1998 Frost Silver SVT E0
17" Masitaly rims with Bridgestone Fuzion ZRi rubber.
133,000km
1996 Silver Ford Taurus SHO ATX
180,000km - SOLD!
1996 Midnight Red SE MTX
295,000km and a little squeeky.
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Joined: Dec 2001
Posts: 667
Veteran CEG\'er
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Veteran CEG\'er
Joined: Dec 2001
Posts: 667 |
Originally posted by Nate Payeur:
They did a test with the engine running and found that there was no signal coming from Bank 1 sensor 2.
I remember reading something about sensor 2 not starting to function until the engine is sufficiently warmed up (since the catalytic converter doesn't start working properly until it gets to a certain temperature, and sensor 2 reads the exhaust of the cat).
Maybe someone else will have some more info...
96 Contour SE
Duratec V6 24-valve 2.5L ATX
108,000 mi.
Replaced: crankshaft w/ DMD, EGR valve (clogged), EVR, DPFE, PCV valve, evap emissions hose & tube (cracked), window regulator (broken), LH & RH PCV tubes, UIM gasket (leak), ignition coil
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Joined: Apr 2002
Posts: 17
New CEG\'er
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New CEG\'er
Joined: Apr 2002
Posts: 17 |
 This past weekend I got rid of code 0420. I It was the Bank 1, sensor 2, down strem sensor after the pre cats. Code has not come back in 5 trips. I had 93k miles on the original 02 sensors and just replaced them all.
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Joined: Jun 2000
Posts: 140
CEG\'er
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OP
CEG\'er
Joined: Jun 2000
Posts: 140 |
Hum, exact same problem as me.
Was it hard to change?
2002 BMW M5
Carbon Black on Black
1998 Frost Silver SVT E0
17" Masitaly rims with Bridgestone Fuzion ZRi rubber.
133,000km
1996 Silver Ford Taurus SHO ATX
180,000km - SOLD!
1996 Midnight Red SE MTX
295,000km and a little squeeky.
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Joined: Sep 2002
Posts: 192
CEG\'er
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CEG\'er
Joined: Sep 2002
Posts: 192 |
I had a 420 5 months ago and replaced the downstream sensor
I just got a 420 after 4 months !!!!!!!!!!!!!! TODAY
EASY to replace for a 420, lay on your back and connector is right there. The easiest of the 4 sensors
1999 GREEN Contour SE SPORT Duratec V6, ATX, SUNROOF, 93,000 Miles, P0420 ON&OFF -replaced DS O2 --did not FIX
*New TORQUE CONVERTER @ 53,000-Intermittent P1744
*New DASH at 53,000 and New DASH lifted-now using MOLLEY bolts to pull down
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Joined: Apr 2002
Posts: 17
New CEG\'er
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New CEG\'er
Joined: Apr 2002
Posts: 17 |
Very easy to replace that sensor, any 7/8" wrench type will do. Sensors were $50, free shipping at ... http://www.oxygensensors.com/
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Joined: Nov 2002
Posts: 216
CEG\'er
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CEG\'er
Joined: Nov 2002
Posts: 216 |
p0420 doesn't mean that the sensor is bad - just the opposite. if the sensor was bad, the pcm wouldn't be able to determine the oxygen holding capacity of the convertors. p0420 indicates that the front to rear switch ratio has exceeded threshold. conditions to test are very particular.
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Joined: Jun 2000
Posts: 140
CEG\'er
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OP
CEG\'er
Joined: Jun 2000
Posts: 140 |
Originally posted by GregH:
p0420 indicates that the front to rear switch ratio has exceeded threshold. conditions to test are very particular.
And so then what has failed? The O2 sensor, the Cat or something else?
2002 BMW M5
Carbon Black on Black
1998 Frost Silver SVT E0
17" Masitaly rims with Bridgestone Fuzion ZRi rubber.
133,000km
1996 Silver Ford Taurus SHO ATX
180,000km - SOLD!
1996 Midnight Red SE MTX
295,000km and a little squeeky.
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Joined: Nov 2002
Posts: 216
CEG\'er
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CEG\'er
Joined: Nov 2002
Posts: 216 |
the catalytic convertor associated with that bank. since both banks typically see the same conditions, getting the code for one bank ususally means replacing both banks.
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