SYSTEM OVERVIEW
The ECM monitors engine operation and contains a self-diagnostic system which stores Diagnostic Trouble Codes (DTCs) and complies to On-Board Diagnostics Generation II (OBD-II) standards. The goal of OBD-II regulation is to provide vehicle with an on-board diagnostic system which is capable of continuously monitoring the efficiency of emission control system, and to improve diagnosis and repair when system failures occur.
The Federal Test Procedure (FTP) sets maximum allowable emission standards. A Malfunction Indicator Light (MIL) must illuminate if a system or component either fails or deteriorates to a point where the vehicle emissions could rise above 1 1/2 times FTP standards.
If malfunction does not reoccur in 3 ignition cycles, the MIL goes off, but DTCs remain recorded in ECM memory. DTCs may only be retrieved using an On-Board Diagnostic (OBD-II) scan tool that complies with SAE standard J-1978 or Lexus scan tool connected to new standardized Data Link Connector (DLC) No. 3. The scan tool also provides freeze-frame data and can be used to clear codes.
Two-Trip Detection Logic
Two-trip detection logic is used to prevent erroneous malfunction detection. When a malfunction initially occurs, Diagnostic Trouble Code (DTC) will be temporarily stored in ECM memory, but MIL on instrument panel will not illuminate.
The second time that a malfunction is detected, MIL on instrument panel will illuminate, provided ignition is turned off and then back on after first malfunction was detected. This is referred to as the 2-Trip Detection Logic and only applies to specified DTCs. See DIAGNOSTIC TROUBLE CODE (DTC) IDENTIFICATION under SELF-DIAGNOSTIC SYSTEM .
DIAGNOSTIC TROUBLE CODE (DTC) IDENTIFICATION
| DTC | Description | Probable Cause |
|---|---|---|
| P0100 (1) | Mass Airflow (MAF) Sensor Circuit Malfunction | Open/Short Circuit, MAF Sensor Or ECM |
| P0101 (1) | Mass Airflow (MAF) Circuit Range/Performance Fault | MAF Sensor |
| P0110 | Intake Air Temperature (IAT) Sensor Circuit | Open/Short Circuit, IAT Sensor Or ECM |
| P0115 | Engine Coolant Temperature (ECT) Sensor Circuit Fault | Open/Short Circuit, ECT Sensor Or ECM |
| P0116 (1) | ECT Sensor Circuit Range/Performance Fault | ECT Sensor Or Cooling System |
| P0120 | Throttle Position (TP) Sensor Malfunction | Open/Short Circuit, TP Sensor Or ECM |
| P0121 (1) | Throttle Position (TP) Sensor Circuit Range/Performance | TP Sensor |
| P0125 | Insufficient Coolant Temperature For Closed Loop | Fuel System, Injection, Ignition System, Exhaust Gas Leakage, Open/Short HO2S Circuit Or HO2S |
| P0130 (1) | (2) Heated Oxygen Sensor Circuit Malfunction (Bank 1, Sensor 1) | HO2S Or Fuel Trim Malfunction |
| P0133 (1) | (2) Heated Oxygen Sensor Circuit Slow Response (Bank 1, Sensor 1) | HO2S |
| P0135 (1) | (2) Heated Oxygen Sensor Heater Circuit Malfunction (Bank 1, Sensor 1) | Open/Short In Heater Circuit, HO2S Or ECM |
| P0136 (1) | (2) Heated Oxygen Sensor Circuit Malfunction (Bank 1, Sensor 2) | HO2S |
| P0141 (1) | (2) Heated Oxygen Sensor Heater Circuit Malfunction (Bank 1, Sensor 2) | Open/Short In Heater Circuit, HO2S Or ECM |
| P0150 (1) | (2) Heated Oxygen Sensor Circuit Malfunction (Bank 2, Sensor 1) | HO2S Or Fuel Trim Malfunction |
| P0153 (1) | (2) Heated Oxygen Sensor Circuit Slow Response (Bank 2, Sensor 1) | HO2S |
| P0155 (1) | (2) Heated Oxygen Sensor Heater Circuit Malfunction (Bank 2, Sensor 1) | Open/Short In Heater Circuit, HO2S Or ECM |
| P0156 (1) | (2) Heated Oxygen Sensor Circuit Malfunction (Bank 2, Sensor 2) | HO2S |
| P0161 (1) | (2) Heated Oxygen Sensor Heater Circuit Malfunction (Bank 2, Sensor 2) | Open/Short In Heater Circuit, HO2S Or ECM |
| P0171 (1) | System Too Lean (Fuel Trim) | Air Hose, Incorrect Fuel Pressure, Injector Blockage, HO2S, MAF Sensor, ECT Sensor Or Exhaust Gas leakage |
| P0172 (1) | System Too Rich (Fuel Trim) | Incorrect Fuel Pressure, Injector Leak Or Blockage, HO2S, MAF Sensor, ECT Sensor Or Exhaust Gas Leakage |
| P0300 | Random Misfire Detected | Ignition, Injector, Incorrect Fuel, Pressure, Compression, Valve Clearance, Valve Timing, MAF Sensor, ECT Sensor, Open/Short Circuit, Loose Connector Or ECM |
| P0301 (1) | Cylinder No. 1 Misfire Detected | Ignition, Injector, Incorrect Fuel, Pressure, Compression, Valve Clearance, Valve Timing, MAF Sensor, ECT Sensor, Open/Short Circuit, Loose Connector Or ECM |
| P0302 (1) | Cylinder No. 2 Misfire Detected | Ignition, Injector, Incorrect Fuel, Pressure, Compression, Valve Clearance, Valve Timing, MAF Sensor, ECT Sensor, Open/Short Circuit, Loose Connector Or ECM |
| P0303 (1) | Cylinder No. 3 Misfire Detected | Ignition, Injector, Incorrect Fuel, Pressure, Compression, Valve Clearance, Valve Timing, MAF Sensor, ECT Sensor, Open/Short Circuit, Loose Connector Or ECM |
| P0304 (1) | Cylinder No. 4 Misfire Detected | Ignition, Injector, Incorrect Fuel, Pressure, Compression, Valve Clearance, Valve Timing, MAF Sensor, ECT Sensor, Open/Short Circuit, Loose Connector Or ECM |
| P0305 (1) | Cylinder No. 5 Misfire Detected | Ignition, Injector, Incorrect Fuel, Pressure, Compression, Valve Clearance, Valve Timing, MAF Sensor, ECT Sensor, Open/Short Circuit, Loose Connector Or ECM |
| P0306 (1) | Cylinder No. 6 Misfire Detected | Ignition, Injector, Incorrect Fuel, Pressure, Compression, Valve Clearance, Valve Timing, MAF Sensor, ECT Sensor, Open/Short Circuit, Loose Connector Or ECM |
| P0325 | Knock Sensor No. 1 Circuit Malfunction | Open/Short Circuit, Loose Sensor Or ECM |
| P0330 | Knock Sensor No. 2 Circuit Malfunction | Open/Short Circuit, Loose Sensor Or ECM |
| P0335 (1) | Crankshaft Position (CKP) Sensor Circuit Malfunction | Open/Short Circuit, CKP Sensor, Starter Or ECM |
| P0340 (1) | Camshaft Position (CMP) Sensor Circuit Malfunction | Open/Short Circuit, CMP Sensor, Starter Or ECM |
| P0420 (1) | Catalyst System Efficiency Below Threshold | Exhaust Gas Leakage, Catalytic Converter, Oxygen Sensor Or Circuit |
| P0430 (1) | Catalyst System Efficiency Below Threshold | Exhaust Gas Leakage, Catalytic Converter, Oxygen Sensor Or Circuit |
| P0440 (1) | EVAP System Malfunction | Vapor Pressure Sensor Or Circuit, Charcoal Canister, Gas Cap, Fuel Tank Or Faulty Vacuum Circuit |
| P0441 (1) | Incorrect EVAP Purge Flow | Open/Short EVAP VSV Circuit, Vapor Pressure Sensor Or Circuit, Charcoal Canister Or Faulty Vacuum Circuit |
| P0446 (1) | EVAP Vent Control Malfunction | Open/Short EVAP VSV Circuit, Vapor Pressure Sensor Or Circuit, Charcoal Canister Or Faulty Vacuum Circuit |
| P0450 | EVAP Pressure Sensor Malfunction | Open/Short Vapor Pressure Sensor Circuit, Vapor Pressure Sensor Or ECM |
| P0451 | EVAP Pressure Sensor Range/Performance | Open/Short Vapor Pressure Sensor Circuit, Vapor Pressure Sensor Or ECM |
| P0500 (1) | Vehicle Speed Sensor Malfunction | Vehicle Speed Sensor Or Circuit, VSS Or ECM |
| P0505 (1) | Idle Control System Malfunction | Electric Throttle Control System Or Loose Intake Air Hose |
| P1120 | Accelerator Pedal Position (APP) Sensor Circuit Malfunction | Open/Short Circuit, APP Sensor Or ECM |
| P1121 | Accelerator Pedal Position (APP) Sensor Range/Performance | APP Sensor Or ECM |
| P1125 | Throttle Control Motor Circuit Fault | Open/Short Circuit, Throttle Control Motor Or ECM |
| P1126 | Magnetic Clutch Circuit Fault | Open/Short Circuit, Magnetic Clutch Or ECM |
| P1127 | Electronic Throttle Control System (ETCS) Fault | Open ETCS Power Circuit Or ECM |
| P1128 | Throttle Control Motor Lock Fault | Throttle Control Motor, Throttle Body Or ECM |
| P1129 | Electronic Throttle Control System (ETCS) Fault | ETCS Or ECM |
| P1300 | Ignitor Circuit Malfunction | Ignitor Circuit To ECM, Ignitor, Coil/Igniter Or ECM |
| P1335 | Crankshaft Position (CKP) Sensor Circuit | Open/Short CKP Sensor Circuit, CKP Sensor Or ECM |
| P1349 | Variable Valve Timing (VVT) System | Valve Timing, Oil Control Valve, VVT Controller Or ECM |
| P1520 (1) | Stoplight Switch Signal Malfunction | Short Circuit, Stoplight Switch Or ECM |
| P1565 (3) | Cruise Control Main Switch Circuit Malfunction | Open/Short Cruise Control Switch Circuit, Cruise Control Switch Or ECM |
| P1600 | ECM BATT Malfunction | ECM Power Source Circuit Or ECM |
| P1633 | ECM Malfunction | ECM |
| P1645 | Body ECU Malfunction | Body ECU, A/C ECU Or Communication Bus |
| P1656 | Oil Control Valve (OCV) Circuit Fault | Open/Short OCV Circuit, OCV Or ECM |
| P1780 (1) | Park/Neutral Position Switch Malfunction | Park/Neutral Position Switch/Circuit Or ECM |
| (1) Two-trip detection logic code. For more information, see DETECTION LOGIC under INTRODUCTION. (2) Bank No. 1 refers to bank that includes cylinder No. 1. Bank No. 2 refers to bank without cylinder No. 1. Sensor No. 1 refers to sensor closest to engine block. (3) This DTC applies to cruise control system. See CRUISE CONTROL SYSTEMS - EXCEPT ES300 article in ACCESSORIES & EQUIPMENT. | ||
| (1) | Two-trip detection logic code. For more information, see DETECTION LOGIC under INTRODUCTION. |
| (2) | Bank No. 1 refers to bank that includes cylinder No. 1. Bank No. 2 refers to bank without cylinder No. 1. Sensor No. 1 refers to sensor closest to engine block. |
| (3) | This DTC applies to cruise control system. See CRUISE CONTROL SYSTEMS - EXCEPT ES300 article in ACCESSORIES & EQUIPMENT. |
DIAGNOSTIC TROUBLE CODE (DTC) IDENTIFICATION