Source wording can vary by vehicle and suffix. It is shown as written, not as a universal diagnosis.
CHEVROLET, GMC
Reported code forms P0421
This technical bulletin provides repair information to correct a customer concern of Service Engine Soon Lamp being illuminated. They may also comment on multiple transmission issues including harsh or delayed shifts,…
RAM
Reported code forms P0421
Flash: Powertrain Control Module (PCM) Updates This bulletin involves reprogramming the Engine Control Module/Powertrain Control Module (ECM/PCM) with the latest available software. The customers may experience a…
RAM
Reported code forms P0421
Flash: Powertrain Control Module (PCM) Updates This bulletin involves reprogramming the Engine Control Module/Powertrain Control Module (ECM/PCM) with the latest available software. The customers may experience a…
CHEVROLET, GMC
Reported code forms P0421
This technical bulletin provides repair information to correct a customer concern of Service Engine Soon Lamp being illuminated with DTCs P2002, P2463, P2459, P144E, P0421, P0422, P0106 P20EE, P129F, P16F3, P20FF,…
CHEVROLET, GMC
Reported code forms P0421
This technical bulletin provides repair information to correct a customer concern of Service Engine Soon Lamp being illuminated. They may also comment on multiple transmission issues including harsh or delayed shifts,…
CHEVROLET, GMC
Reported code forms P0421
This technical bulletin provides repair information to correct a customer concern of Service Engine Soon Lamp Illuminated, Harsh or Delayed Transmission Shifts Including Slip, Surge, Shudder, Noise, Whine, Growl, Shake…
RAM
Reported code forms P0421
Flash: Powertrain Control Module (PCM) Updates This bulletin involves reprogramming the Engine Control Module/Powertrain Control Module (ECM/PCM) with the latest available software. The customers may experience a…
RAM
Reported code forms P0421
Flash: Powertrain Control Module (PCM) Updates This bulletin involves reprogramming the Engine Control Module/Powertrain Control Module (ECM/PCM) with the latest available software. The customers may experience a…
RAM
Reported code forms P0421-00
Flash: Powertrain Control Module (PCM) Updates This bulletin involves reprogramming the Engine Control Module (ECM) / Powertrain Control Module (PCM) with the latest available software. Customers may experience a…
RAM
Reported code forms P0421-00
Flash: Powertrain Control Module (PCM) Updates This bulletin involves reprogramming the Engine Control Module (ECM) / Powertrain Control Module (PCM) with the latest available software. Customers may experience a…
HINO
Reported code forms P0421
SB-20-001 If a truck comes to the dealer with a MIL lamp illuminated with the Diagnostic Trouble Code (DTC): P0421 –Determination of ATC Deterioration. Certain 16MY-20MYCab-Over Engine (COE) Trucks equipped with a J05…
RAM
Reported code forms P0421-00
Flash: Powertrain Control Module (PCM) Updates This bulletin involves reprogramming the Engine Control Module/Powertrain Control Module (ECM/PCM) with the latest available software. Customers may experience a…
CHEVROLET, GMC
Reported code forms P0421
18209 - Service Update. Certain vehicles equipped with a 1.6L diesel engine (RPO LH7), may have been built with an improper alignment of the clamp/gasket assembly connecting the turbocharger to the catalytic converter.…
CHEVROLET, GMC
Reported code forms P0421
This technical bulletin provides a procedure to reposition the exhaust clamp to correct a condition of Exhaust Smell in Cabin and/or DTC P0421 Set due to a miss installed clamp.
RAM
Reported code forms P0421
Flash: 6.7L Diagnostic and System Improvements This bulletin involves reprogramming the Engine Control Module/Powertrain Control Module (ECM/PCM) with the latest available software. The following Diagnostic Trouble…
CHEVROLET
Reported code forms P0421
This engineering informational bulletin is requesting information from the field on vehicles that have the condition of Malfunction Indicator Lamp Illuminated and DTC P0421 Set.
CHEVROLET
Reported code forms P0421
Engineering Information – Malfunction Indicator Lamp Illuminated and DTC P0421 Set
RAM
Reported code forms P0421
Flash: 6.7L Diagnostic And System Improvements This bulletin involves reprogramming the Engine Control Module/Powertrain Control Module (ECM/PCM) with the latest available software. The following Diagnostic Trouble…
RAM
Reported code forms P0421
Flash: 6.7L Diagnostic And System Improvements This bulletin involves reprogramming the Engine Control Module/Powertrain Control Module (ECM/PCM) with the latest available software. The following Diagnostic Trouble…
RAM
Reported code forms P0421
Flash: 6.7L Diagnostic And System Improvements This bulletin involves reprogramming the Engine Control Module/Powertrain Control Module (ECM/PCM) with the latest available software. The following Diagnostic Trouble…
RAM
Reported code forms P0421
Flash: 6.7L Diagnostic And System Improvements This bulletin involves reprogramming the Engine Control Module/Powertrain Control Module (ECM/PCM) with the latest available software. The following DTCs have been changed…
RAM
Reported code forms P0421
Flash: 6.7L Diagnostic And System Improvements This bulletin involves reprogramming the Engine Control Module/Powertrain Control Module (ECM/PCM) with the latest available software. The following DTCs have been changed…
RAM
Reported code forms P0421
Flash: 6.7L Diagnostic And System Improvements This bulletin involves reprogramming the Engine Control Module/Powertrain Control Module (ECM/PCM) with the latest available software. DTCs have been changed from a one…
RAM
Reported code forms P0421
Flash: 6.7L Diagnostic And System Improvements This bulletin involves reprogramming the Engine Control Module/Powertrain Control Module (ECM/PCM) with the latest available software. DTCs have been changed from a one…
MAZDA
Reported code forms P0421 P0421:00
SOME VEHICLES MAY EXPERIENCE THE CHECK ENGINE LIGHT ON WITH DTC P0421:00 (CATALYTIC CONVERTER SYSTEM) WITH-OUT EXPERIENCING POOR ENGINE PERFORMANCE OR MISFIRE (MITSUBISHI PCM ONLY).THIS IS CAUSED BY IMPROPER CONTROL…
MAZDA
Reported code forms P0421 P0421:00
SOME VEHICLES MAY EXPERIENCE THE CHECK ENGINE LIGHT ON WITH DTC P0421:00 (CATALYTIC CONVERTER SYSTEM) WITHOUT EXPERIENCING POOR ENGINE PERFORMANCE OR MISFIRE (MITSUBISHI PCM ONLY). THIS IS CAUSED BY IMPROPER CONTROL…
HINO
Reported code forms P0421
ECU False P0421 DTC Detection. A subject vehicle may exhibit an illuminated MIL (Malfunction Indicator Lamp) with DTC (Diagnostic Trouble Code) P0421 (ATC Dtc Deterioration Monitoring). The engine ECU may falsely detect…
HINO
Reported code forms P0421
AA0H0 A subject vehicle may exhibit an illuminated MIL (Malfunction Indicator Lamp) with DTC (Diagnostic Trouble Code) P0421 (ATC Deterioration Monitoring). The engine ECU may falsely detect an issue with the ATC (After…
HINO
Reported code forms P0421
SB-15-003 CORRECTION OF WORKSHOP MANUAL FOR HINO 2015MY (REVISION OF TROUBLESHOOTING PROCEDURE FOR THE DTC P0421)
HINO
Reported code forms P0421
A subject vehicle may exhibit an illuminated check engine lamp with DTC (Diagnostic Trouble Code) P0421 (Catalyst efficiency below threshold). The engine ECU may falsely detect an issue with the ATC (After Turbo…