P0421 Diagnostic Trouble Code Discussion for July 2009
Warmup Catalyst Efficiency Low (Bank 1)
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| Help Request | Posted | |
| 1998 Mazda Protege DX 1.5L Poor Idle Quality, Surge, MIL Lamp on VIN: JM1BC1414W P0421: Warmup Catalyst Efficiency Below Normal (Bank 1). ... 0170 ,p 0300 ,p 0421, p1170 faults recorded check for intake leaks and for ignition leaks none found plugs look good new customer could use alittle help thanks |
July 22, 2009 | |
| 2001 Hyundai Santa Fe GL 2.4L Cuts out VIN: KM8SB82B91 P0421: Warmup Catalyst Efficiency Below Normal (Bank 1). Hi Techs, I'm pulling my hair out on this one. After a through warm up, at slow speeds the engine will start fluttering and will die out at a stop, it will restart easy. It did it for me twice in three days and I had the Modis on it the 2d time. The Modis show... |
July 31, 2009 |
