Join Now
International Automotive Technicians Network

P0420 Diagnostic Trouble Code Discussion for August 2007

Catalyst Efficiency Below Normal (Bank 1)


Note: This is a professional automotive technician's resource.
Vehicle Owners: If you are seeking an automotive repair professional to service your vehicle, visit the iATN Repair Shop Finder.

Trouble Ticket Help Requests for DTC P0420
Help Request Posted
2002 Buick Century Custom 3.1L MIL Lamp on
P0420: Catalyst System Low Efficiency. Vehicle came in with P0420 Cat effciency code. Checked o2's and found these strange readings. At idle pre cat o2 working fine. Post cat o2 sitting @ .400mv. LTFT -4%. Then when revved to 2500 in park... LTFT goes to -14/-16%. Pre cat o2 still toggles great. Po...
August 09, 2007
2003 Audi A4 1.8L MIL Lamp on VIN: WAUJC68E63
P0420: cat not efficient cyl.1. This Audi came in with the above codes. Thought maybe the low voltage code may be a sign of what caused the misfire codes, so checked power at term#3 of control moduel, and grounds at Terms# 1$2. All check ok, grounds are clean and tight under the abs pump. Al...
August 13, 2007
2001 Nissan Pathfinder LE 3.5L Misfire, MIL Lamp on, p1320 VIN: JN8DR07Y41
P0420: Catalyst Efficiency Below Normal (Bank 1). ... concern of runninh rough and light comming on intermitantly. at that time we found the 2 pending codes. p0420b p1320. we replaced the b1 cat and returned vehicl to customer. car came back with hard failures p0302 #2 missfire and p1320 primery ignition sign...
August 17, 2007
1997 GMC Safari SLE 4.3L MIL Lamp on VIN: 1GKDM19W8V
P0420: Catalyst System Low Efficiency (Bank 1). ... the freeway. Pulled over and restarted with a high idle. Drove it home and the next day it started and stalled three times. After that it ran perfectly fine. A couple of days later the check engine light comes on. (I'm assuming it had an IAC problem) They ...
August 20, 2007
1998 Honda Accord LX 2.3L MIL Lamp on VIN: 1HGCG5644W
P0420: Catalyst Efficiency Below Threshold (Bank 1). ... P0420 Cat. effic. for the last 2 years and I am out of ideas and need help.It started 8/23/05 with the P0420 code & I cleared the code because every thing looked good with the scan tool. Told them to let me know if it came back on, that was at 119471 M...
August 24, 2007
1998 Honda Accord LX 2.3L MIL Lamp on VIN: 1HGCG5644W
P0420: Catalyst Efficiency Below Threshold (Bank 1). ... P0420 Cat. effic. for the last 2 years and I am out of ideas and need help.It started 8/23/05 with the P0420 code & I cleared the code because every thing looked good with the scan tool. Told them to let me know if it came back on, that was at 119471 M...
August 27, 2007
1999 Mazda Protege DX 1.6L no mil light VIN: JM1BJ2226X
P0420: Catalyst Efficiency Below Normal (Bank 1). I replace pcm with a mazda reman. and the same thing happens. 02 sensor look like they mimick eachother and have a new cat. Why is a code set but not turning on check engine light and why is no pending codes not setting the code this is really baffling me. ple...
August 30, 2007
1999 Mazda Protege DX 1.6L no mil light VIN: JM1BJ2226X
P0420: Catalyst Efficiency Below Normal (Bank 1). I replace pcm with a mazda reman. and the same thing happens. 02 sensor look like they mimick eachother and have a new cat. Why is a code set but not turning on check engine light and why is no pending codes not setting the code this is really baffling me. ple...
August 31, 2007
2002 Buick Century Custom 3.1L MIL Lamp on
P0420: Catalyst System Low Efficiency. Vehicle came in with P0420 Cat effciency code. Checked o2's and found these strange readings. At idle pre cat o2 working fine. Post cat o2 sitting @ .400mv. LTFT -4%. Then when revved to 2500 in park... LTFT goes to -14/-16%. Pre cat o2 still toggles great. Po...
August 09, 2007
2003 Audi A4 1.8L MIL Lamp on VIN: WAUJC68E63
P0420: cat not efficient cyl.1. This Audi came in with the above codes. Thought maybe the low voltage code may be a sign of what caused the misfire codes, so checked power at term#3 of control moduel, and grounds at Terms# 1$2. All check ok, grounds are clean and tight under the abs pump. Al...
August 13, 2007
2001 Nissan Pathfinder LE 3.5L Misfire, MIL Lamp on, p1320 VIN: JN8DR07Y41
P0420: Catalyst Efficiency Below Normal (Bank 1). ... concern of runninh rough and light comming on intermitantly. at that time we found the 2 pending codes. p0420b p1320. we replaced the b1 cat and returned vehicl to customer. car came back with hard failures p0302 #2 missfire and p1320 primery ignition sign...
August 17, 2007
1997 GMC Safari SLE 4.3L MIL Lamp on VIN: 1GKDM19W8V
P0420: Catalyst System Low Efficiency (Bank 1). ... the freeway. Pulled over and restarted with a high idle. Drove it home and the next day it started and stalled three times. After that it ran perfectly fine. A couple of days later the check engine light comes on. (I'm assuming it had an IAC problem) They ...
August 20, 2007
1998 Honda Accord LX 2.3L MIL Lamp on VIN: 1HGCG5644W
P0420: Catalyst Efficiency Below Threshold (Bank 1). ... P0420 Cat. effic. for the last 2 years and I am out of ideas and need help.It started 8/23/05 with the P0420 code & I cleared the code because every thing looked good with the scan tool. Told them to let me know if it came back on, that was at 119471 M...
August 24, 2007
1998 Honda Accord LX 2.3L MIL Lamp on VIN: 1HGCG5644W
P0420: Catalyst Efficiency Below Threshold (Bank 1). ... P0420 Cat. effic. for the last 2 years and I am out of ideas and need help.It started 8/23/05 with the P0420 code & I cleared the code because every thing looked good with the scan tool. Told them to let me know if it came back on, that was at 119471 M...
August 27, 2007
1999 Mazda Protege DX 1.6L no mil light VIN: JM1BJ2226X
P0420: Catalyst Efficiency Below Normal (Bank 1). I replace pcm with a mazda reman. and the same thing happens. 02 sensor look like they mimick eachother and have a new cat. Why is a code set but not turning on check engine light and why is no pending codes not setting the code this is really baffling me. ple...
August 30, 2007
1999 Mazda Protege DX 1.6L no mil light VIN: JM1BJ2226X
P0420: Catalyst Efficiency Below Normal (Bank 1). I replace pcm with a mazda reman. and the same thing happens. 02 sensor look like they mimick eachother and have a new cat. Why is a code set but not turning on check engine light and why is no pending codes not setting the code this is really baffling me. ple...
August 31, 2007