P40xx OBD-II Codes (P4000–P4099)

100 fault codes in the P40xx range. Click any code for causes, diagnostic steps, severity, and common fixes.

P4000 critical
Exhaust Gas Temperature Sensor Circuit Bank 1 Sensor 1 Open (Generic)
P4001 moderate
Exhaust Gas Temperature Sensor Circuit Bank 1 Sensor 1 Low (Generic)
P4002 moderate
Exhaust Gas Temperature Sensor Circuit Bank 1 Sensor 1 High (Generic)
P4003 moderate
Exhaust Gas Temperature Sensor Circuit Bank 1 Sensor 1 Intermittent (Generic)
P4004 critical
Exhaust Gas Temperature Sensor Circuit Bank 1 Sensor 2 Open (Generic)
P4005 moderate
Exhaust Gas Temperature Sensor Circuit Bank 1 Sensor 2 Low (Generic)
P4006 moderate
Exhaust Gas Temperature Sensor Circuit Bank 1 Sensor 2 High (Generic)
P4007 moderate
Exhaust Gas Temperature Sensor Circuit Bank 1 Sensor 2 Intermittent (Generic)
P4008 critical
Exhaust Gas Temperature Sensor Circuit Bank 2 Sensor 1 Open (Generic)
P4009 moderate
Exhaust Gas Temperature Sensor Circuit Bank 2 Sensor 1 Low (Generic)
P4010 moderate
Exhaust Gas Temperature Sensor Circuit Bank 2 Sensor 1 High (Generic)
P4011 moderate
Exhaust Gas Temperature Sensor Circuit Bank 2 Sensor 1 Intermittent (Generic)
P4012 critical
Exhaust Gas Temperature Sensor Circuit Bank 2 Sensor 2 Open (Generic)
P4013 moderate
Exhaust Gas Temperature Sensor Circuit Bank 2 Sensor 2 Low (Generic)
P4014 moderate
Exhaust Gas Temperature Sensor Circuit Bank 2 Sensor 2 High (Generic)
P4015 moderate
Exhaust Gas Temperature Sensor Circuit Bank 2 Sensor 2 Intermittent (Generic)
P4016 critical
Catalyst Temperature Sensor Circuit Bank 1 Open (Generic)
P4017 moderate
Catalyst Temperature Sensor Circuit Bank 1 Low (Generic)
P4018 moderate
Catalyst Temperature Sensor Circuit Bank 1 High (Generic)
P4019 moderate
Catalyst Temperature Sensor Circuit Bank 1 Intermittent (Generic)
P4020 critical
Catalyst Temperature Sensor Circuit Bank 2 Open (Generic)
P4021 moderate
Catalyst Temperature Sensor Circuit Bank 2 Low (Generic)
P4022 moderate
Catalyst Temperature Sensor Circuit Bank 2 High (Generic)
P4023 moderate
Catalyst Temperature Sensor Circuit Bank 2 Intermittent (Generic)
P4024 critical
NOx Sensor Circuit Bank 1 Open (Generic)
P4025 moderate
NOx Sensor Circuit Bank 1 Range/Performance (Generic)
P4026 moderate
NOx Sensor Circuit Bank 1 Low Input (Generic)
P4027 moderate
NOx Sensor Circuit Bank 1 High Input (Generic)
P4028 critical
NOx Sensor Circuit Bank 2 Open (Generic)
P4029 moderate
NOx Sensor Circuit Bank 2 Range/Performance (Generic)
P4030 moderate
NOx Sensor Heater Circuit Bank 1 Malfunction (Generic)
P4031 moderate
NOx Sensor Heater Circuit Bank 2 Malfunction (Generic)
P4032 critical
Particulate Matter Sensor Circuit Open (Generic)
P4033 moderate
Particulate Matter Sensor Circuit Low (Generic)
P4034 moderate
Particulate Matter Sensor Circuit High (Generic)
P4035 moderate
Particulate Matter Sensor Circuit Intermittent (Generic)
P4036 critical
Exhaust Pressure Sensor Circuit Open (Generic)
P4037 moderate
Exhaust Pressure Sensor Circuit Low (Generic)
P4038 moderate
Exhaust Pressure Sensor Circuit High (Generic)
P4039 moderate
Exhaust Pressure Sensor Circuit Intermittent (Generic)
P4040 moderate
Exhaust Gas Recirculation Temperature Sensor Circuit Open (Generic)
P4041 moderate
Exhaust Gas Recirculation Temperature Sensor Circuit Low (Generic)
P4042 moderate
Exhaust Gas Recirculation Temperature Sensor Circuit High (Generic)
P4043 low
Exhaust Gas Recirculation Temperature Sensor Circuit Intermittent (Generic)
P4044 critical
Turbo Boost Pressure Sensor Circuit Bank 1 Open (Generic)
P4045 moderate
Turbo Boost Pressure Sensor Circuit Bank 1 Low (Generic)
P4046 moderate
Turbo Boost Pressure Sensor Circuit Bank 1 High (Generic)
P4047 moderate
Turbo Boost Pressure Sensor Circuit Bank 1 Intermittent (Generic)
P4048 critical
Turbo Boost Pressure Sensor Circuit Bank 2 Open (Generic)
P4049 moderate
Turbo Boost Pressure Sensor Circuit Bank 2 Low (Generic)
P4050 moderate
Turbo Boost Pressure Sensor Circuit Bank 2 High (Generic)
P4051 moderate
Turbo Boost Pressure Sensor Circuit Bank 2 Intermittent (Generic)
P4052 moderate
EGR Cooler Bypass Valve Control Circuit Open (Generic)
P4053 moderate
EGR Cooler Bypass Valve Control Circuit Low (Generic)
P4054 moderate
EGR Cooler Bypass Valve Control Circuit High (Generic)
P4055 low
EGR Cooler Bypass Valve Control Circuit Intermittent (Generic)
P4056 critical
Exhaust Aftertreatment Fuel Injector Circuit Open (Generic)
P4057 moderate
Exhaust Aftertreatment Fuel Injector Circuit Low (Generic)
P4058 moderate
Exhaust Aftertreatment Fuel Injector Circuit High (Generic)
P4059 moderate
Exhaust Aftertreatment Fuel Injector Circuit Intermittent (Generic)
P4060 critical
DEF Dosing Valve Circuit Open (Generic)
P4061 moderate
DEF Dosing Valve Circuit Low (Generic)
P4062 moderate
DEF Dosing Valve Circuit High (Generic)
P4063 moderate
DEF Quality Sensor Circuit Malfunction (Generic)
P4064 moderate
DEF Level Sensor Circuit Malfunction (Generic)
P4065 moderate
DEF Temperature Sensor Circuit Malfunction (Generic)
P4066 critical
DEF Pump Circuit Open (Generic)
P4067 moderate
DEF Pump Circuit Low (Generic)
P4068 moderate
DEF Pump Circuit High (Generic)
P4069 moderate
Exhaust Backpressure Valve Circuit Open (Generic)
P4070 moderate
Exhaust Backpressure Valve Circuit Low (Generic)
P4071 moderate
Exhaust Backpressure Valve Circuit High (Generic)
P4072 critical
SCR Catalyst Efficiency Below Threshold Bank 1 (Generic)
P4073 critical
SCR Catalyst Efficiency Below Threshold Bank 2 (Generic)
P4074 moderate
DPF Differential Pressure Sensor Correlation Error (Generic)
P4075 critical
DPF Soot Load Above Threshold (Generic)
P4076 moderate
DPF Ash Load Above Threshold (Generic)
P4077 critical
Exhaust Temperature Too High for DPF Regeneration (Generic)
P4078 moderate
Exhaust Pressure Control Valve Position Sensor Circuit Open (Generic)
P4079 moderate
Exhaust Pressure Control Valve Position Sensor Circuit Low (Generic)
P4080 moderate
Exhaust Pressure Control Valve Position Sensor Circuit High (Generic)
P4081 low
Exhaust Pressure Control Valve Position Sensor Intermittent (Generic)
P4082 critical
Diesel Oxidation Catalyst Temperature Sensor Circuit Open (Generic)
P4083 moderate
Diesel Oxidation Catalyst Temperature Sensor Circuit Low (Generic)
P4084 moderate
Diesel Oxidation Catalyst Temperature Sensor Circuit High (Generic)
P4085 moderate
Diesel Oxidation Catalyst Temperature Sensor Circuit Intermittent (Generic)
P4086 critical
Exhaust Aftertreatment System Performance Below Threshold (Generic)
P4087 low
Exhaust Aftertreatment System Monitoring Incomplete (Generic)
P4088 critical
Turbo Vane Position Sensor Circuit Open (Generic)
P4089 moderate
Turbo Vane Position Sensor Circuit Low (Generic)
P4090 moderate
Turbo Vane Position Sensor Circuit High (Generic)
P4091 moderate
Turbo Vane Position Sensor Circuit Intermittent (Generic)
P4092 critical
Turbo Wastegate Control Valve Circuit Open (Generic)
P4093 moderate
Turbo Wastegate Control Valve Circuit Low (Generic)
P4094 moderate
Turbo Wastegate Control Valve Circuit High (Generic)
P4095 moderate
Turbo Wastegate Control Valve Circuit Intermittent (Generic)
P4096 critical
Diesel Throttle Valve Position Sensor Circuit Open (Generic)
P4097 moderate
Diesel Throttle Valve Position Sensor Circuit Low (Generic)
P4098 moderate
Diesel Throttle Valve Position Sensor Circuit High (Generic)
P4099 low
Diesel Throttle Valve Position Sensor Circuit Intermittent (Generic)
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