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P0420 Diagnostic Trouble Code Discussion for September 2007

Catalyst Efficiency Below Normal (Bank 1)

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Trouble Ticket Help Requests for DTC P0420
Help Request Posted
2001 Infiniti QX4 3.5L Surge VIN: JNRDR07Y31
P0420: Catalyst Efficiency Below Normal (Bank 1). hi all, this qx4 came in for a 90k and a smog. the 90k went well, changed plugs with same brand and part#, test drove great. problem, smog machine ask's for 2 speed idle test. while trying to perform the 2500 rpm part of the test, the engine will surge about 4...
September 05, 2007
2000 Nissan Maxima GLE 3.0L MIL Lamp on VIN: JN1CA31D8Y
P0420: Catalyst Efficiency Below Normal (Bank 1). Came in with two codes P0400 & P0420. Cleared codes, let it cool down. Went through the test drive, and the P0400 came back. While driving it I was watcing the EGR Temp, and the EGR control. I didn't notice much temp cange wen te valve was opening or closi...
September 07, 2007
2004 Ford F-150 FX4 5.4L MIL Lamp on, pinging, plug broken VIN: 1FTPX14534
P0420: catalyst effciency monitor and exhaust system. Well this has been fun, first we found these cat codes and did a test drive. The complants are mil light on and it pings occationly. Basicly the o2 apear to be working properly, even after a good 6 mile run the rear o2s and front o2s are identical, which tells...
September 17, 2007
1998 Pontiac Grand Prix GT 3.8L No Start, Cuts out, Stall, Misfire, MIL Lamp on VIN: 1G2WP12K8W
P0420: Catalyst System Low Efficiency (Bank 1). ... driving down express way vehicle will stall out and nothing will happen. Never loses voltage just will not start. Scanned Vehile and und mil code there were: p0440, p0442,p0336, p0420 Und...
September 17, 2007
1999 Chevrolet Blazer 4.3L Poor Idle Quality, Misfire, Poor Fuel Economy, MIL Lamp on VIN: 1GNDT13WXX
P0420: Catalyst System Low Efficiency (Bank 1). hey guy me again i want to thank you all again for all the help and info it worked wonders lets say i am now a gm man not all that complex rpo and vin codes i recomend learning it helps alot anyways i need to find out how to clean the intake on the blazer quic...
September 21, 2007
2001 Chevrolet Camaro 3.8L MIL Lamp on VIN: 2G1FP22K61
P0420: Catalyst System Low Efficiency. hello, this vehicle came in with code po420, the first thing i did was raised vehilce up and banged on cat and sure enough there was stuff bouncing around in the cat. the customer chose to have the cat put on at a muffler shop. he brought it back i cleared cod...
September 25, 2007
2001 Chevrolet Impala LS 3.8L MIL Lamp on VIN: 2G1WH55K91
P0420: Catalyst System Low Efficiency. Vehicle owner complains of SES light on with no driveability issues. Code PO420 keeps returning. The previous shop has replaced the Catalytic Converter 3 times with a direct fit, installed both 02 sensors and a Mass Air Flow Sensor. The problem keeps returning...
September 25, 2007
2002 Cadillac DeVille DTS 4.6L MIL Lamp on VIN: 1G6KF57982
P0420: Catalyst System Low Efficiency - Bank 1 (California). Thanks in advance for your help. Car came in originally with both o2s switch identically. Car has no drivablity issues. Fuel control is plus or minus 2%. We sold the cat and now cat lights off and second o2 flat lines but code still returns within a week. Is t...
September 27, 2007
2002 Chevrolet Impala 3.4L MIL Lamp on VIN: 2G1WF55E72
P0420: Catalyst System Low Efficiency. Car came in with P0420 code (Catalyst System Low Efficiency) running fine. Checked the rear O2 sensor and found too much activity. Replaced the after market cat with OEM cat and rear O2 sensor. Drove the car two miles and P0420 code came back. Rechecking, I f...
September 27, 2007