OBD-II reference
Don't buy the expensive part first.
OBD-II trouble codes, diagnosed in the right order
Plug in a reader, get a code, look it up here. Every code gets the same treatment: what the computer actually measured, what it usually turns out to be, the one test that separates the cheap repair from the expensive one, and what it really costs.
A code reports a failed test, not a broken part. The difference is usually worth a few hundred dollars.
All codes 23
P0011
"A" Camshaft Position - Timing Over-Advanced or System Performance (Bank 1)
Top starting point: Low, dirty or incorrect-viscosity engine oil ·
32% editorial estimate
P0101
Mass or Volume Air Flow "A" Circuit Range/Performance Problem
Top starting point: Contaminated mass-airflow sensing element ·
27% editorial estimate
P0113
Intake Air Temperature Sensor 1 Circuit High Input
Top starting point: Loose connector, pushed-out pin or spread terminal ·
28% editorial estimate
P0128
Coolant Thermostat Below Regulating Temperature
Top starting point: Thermostat stuck open ·
64% editorial estimate
P0135
Oxygen Sensor Heater Circuit Malfunction (Bank 1, Sensor 1)
Top starting point: Open or failed heater inside Bank 1 Sensor 1 ·
34% editorial estimate
P0141
Oxygen Sensor Heater Circuit Malfunction (Bank 1, Sensor 2)
Top starting point: Open or failed heater inside Bank 1 Sensor 2 ·
33% editorial estimate
P0171
System Too Lean (Bank 1)
Top starting point: Unmetered air leak — vacuum hose, intake boot or gasket ·
42% editorial estimate
P0172
System Too Rich (Bank 1)
Top starting point: Leaking or over-delivering fuel injector ·
27% editorial estimate
P0174
System Too Lean (Bank 2)
Top starting point: Intake or vacuum leak affecting bank two ·
36% editorial estimate
P0234
Turbocharger/Supercharger A Overboost Condition
Top starting point: Sticking wastegate, bypass valve or variable turbo vanes ·
28% editorial estimate
P0299
Turbocharger/Supercharger A Underboost Condition
Top starting point: Split, loose or swollen charge-air hose or intercooler leak ·
30% editorial estimate
P0300
Random / Multiple Cylinder Misfire Detected
Top starting point: Worn spark plugs, coils or leads ·
38% editorial estimate
P0301
Cylinder 1 Misfire Detected
Top starting point: Worn or fouled spark plug on cylinder one ·
28% editorial estimate
P0325
Knock Sensor 1 Circuit (Bank 1 or Single Sensor)
Top starting point: Chafed, open or shorted wiring and loose connector terminals ·
29% editorial estimate
P0335
Crankshaft Position Sensor A Circuit Malfunction
Top starting point: Failed crankshaft position sensor ·
30% editorial estimate
P0340
Camshaft Position Sensor A Circuit (Bank 1 or Single Sensor)
Top starting point: Failed camshaft position sensor ·
28% editorial estimate
P0401
Exhaust Gas Recirculation Flow Insufficient
Top starting point: Carbon-blocked EGR passages ·
45% editorial estimate
P0420
Catalyst System Efficiency Below Threshold (Bank 1)
Top starting point: Catalytic converter genuinely worn out ·
40% editorial estimate
P0430
Catalyst System Efficiency Below Threshold (Bank 2)
Top starting point: Bank 2 catalytic converter genuinely degraded ·
38% editorial estimate
P0442
Evaporative Emission System Leak Detected (Small Leak)
Top starting point: Fuel-cap seal hardened, cracked or contaminated ·
28% editorial estimate
P0455
Evaporative Emission System Leak Detected (Large Leak)
Top starting point: Fuel cap loose, cross-threaded or with a perished seal ·
45% editorial estimate
P0507
Idle Control System RPM Higher Than Expected
Top starting point: Vacuum or intake leak bypassing the throttle ·
32% editorial estimate
P0700
Transmission Control System Malfunction (MIL Request)
Top starting point: A specific sensor, solenoid or pressure DTC stored in the TCM ·
30% editorial estimate