Toyota Avalon, Camry, Camry Solara 2001-06

OBD II Systems & Terminology

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Diagnostic Trouble Code (DTC) Explanation



Diagnostic Trouble Codes
DTC Numbering Explanation

The number in the hundredth position indicates the specific vehicle system or sub-group in which the failure occurred.



Click image to see an enlarged view

Fig.

This position should be consistent for P0xxx and P1xxx type codes.

An example of how to interpret an OBD II code is shown in the Graphic to the right.

The Society of Automotive Engineers (SAE) developed the numbers and systems in the list that follows:

P0100 - Air Metering and Fuel System fault

P0200 - Fuel System (fuel injector only) fault

P0300 - Ignition System or Misfire fault

P0400 - Emission Control System fault

P0500 - Idle Speed Control, Vehicle Speed Sensor fault

P0600 - Computer Output Circuit (relay, solenoid, etc.) fault

P0700 - Transaxle, Transmission faults

Note: The first and tenth digits indicate the type of Emission System that has failed.

OBD II Warmup Cycle

Once a MIL is off, the trouble code will remain in memory until 40 warmup cycles are completed without the same fault reoccurring.

A warmup cycle is defined as a trip that includes a change in engine temperature of at least 40F, and where the engine tempe rature reaches at least 160F.



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Fig.

Freeze Frame Data



Carb And Toyota Enhanced Signals
Refer to the list of CARB Mandated and Toyota Enhanced Signals.
CARB Mandated SignalsTOYOTA Enhanced Signals
A/FS (A/F) Bank 1 Sensor 2 (Volts)A/C Signal (On/Off)
A/FS (A/F) Bank 1 Sensor 2 (%)A/C Cut Signal (On/Off)
Calculated Load (%)A/C Magnetic Clutch Signal (On/Off)
Coolant Temperature (C or F)Closed Throttle Position Switch (On/Off)
Engine Speed (RPM)Cylinder 1-6 (Abnormal Variation)
Fuel System Bank 1 (%)EGR System (On/Off)
Ignition Advance (Degrees)Electronic Load Signal (On/Off)
Intake Air Temperature (C or F)EVAP Purge VSV (On/Off)
Long Term Fuel Trim (%)EVAP Vapor Pressure VSV (On/Off)
Manifold Air Pressure Sensor (kPa)Fuel Cut Idle (On/OFF)
O2S Bank 1 Sensor 1 (Volts)Fuel Cut TAU - High Load (On/Off)
O2S Bank 1 Sensor 2 (Volts)Fuel Pump (On/Off)
O2S Bank 1 Sensor 1 (%)Idle Air Control Duty Ratio (%)
Short Term Fuel Trim (%)Ignition Counts (0-2000 counts)
Throttle Position (% of opening)Injector Pulsewidth (ms)
Vehicle Speed (KPH/MPH)Misfire Engine Speed (RPM)
---Misfire Load (g/r)
---O2S L/R Sensor 2 (0-1000ms)
---O2S R/L Sensor 2 (0-1000ms)
---Park Neutral Position (On/OFF)
---Power Steering Oil Press (On/Off)
---Starter Signal (On during cranking)
---Stop Light Switch (On/Off)
  Total Fuel Trim Bank 1 (%)
Freeze Frame Data

OBD II Regulations (CARB and EPA) require that the vehicle onboard computer store specific Freeze Frame Data when the first emission-related fault is detected. The current readings can only be overwritten by data from the Fuel System or Misfire Monitor.

Freeze Frame Data must contain the engine operating conditions present at the time a code is set. OBD II systems record Freeze Frame Data at the time an emission-related DTC is recorded and the MIL is activated. This data must appear in standard measurements.

Freeze Frame Data can be thought of as a recording of one frame in time. This data contains details that describe the engine operating conditions at the instant a fault is detected and a code is set.

OBD II Certified Scan Tools

An OBD II Certified Scan Tool should be able to display Current, Pending or History Codes, MIL on or off requests, Freeze Frame Data, I/M Readiness Status and Last Test Pass or Fail Messages.

Malfunction Indicator Lamp



OBD II regulations (CARB and EPA) require that a Malfunction Indicator Lamp (MIL) be illuminated when a fault is detected, and that a Diagnostic Trouble Code (DTC) is stored in the PCM memory.

EVAP System Monitor

OBD II regulations require that EVAP system operation be monitored for the correct airflow used to purge the EVAP system. These EVAP systems are monitored using a pressure check to verify that no leaks exist that could allow fuel vapors to escape into the atmosphere. If a leak equal to or greater than 0.040" (0.020" in 2001-02) is detected in the EVAP system for two consecutive trips, a trouble code is set.

The EVAP VSV and Vapor Pressure sensor are used to detect faults in the system. If the PCM detects a fault in one of the devices shown in the Graphic, it sets DTC P0440. If DTC P0441, P0446 or P0450 are set along with DTC P0440, repair these trouble codes first.



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Fig.

Diagnosis Of DTC P0441 And P0446

The VSV for the Vapor Pressure sensor and the Vapor Pressure sensor are used by the PCM to detect faults in the EVAP system.

The PCM determines if there is a fault in the EVAP system based on the Vapor Pressure signal. If the PCM detects a leak or a fault in any of the components within the dotted line in Graphic below, it will set DTC P0441 or P0446 (depending upon the type of fault that exists).



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Fig.

EVAP System Monitor "Trip" Pattern

The "trip" pattern can be used to validate an EVAP DTC (i.e., P0440) or to "run" the EVAP Monitor to complete the Inspection/Maintenance (I/M) Readiness Test.



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Fig.

P0440 Code Conditions (2-Trip Detection)

The PCM will set P0440 if it detects the following condition:



The fuel tank pressure is near atmospheric pressure after the vehicle is driven for 20 minutes (look for a loose or missing cap).
 

P0441 Code Conditions (2-Trip Detection)

The PCM will set P0441 if it detects one of the following conditions:



The pressure in the canister does not drop during purge control.
 
During purge cutoff, if the pressure in the charcoal canister is very low when compared to the atmospheric pressure value.
 

P0446 Code Conditions (2-Trip Detection)

The PCM will set P0446 of one of the following conditions is detected:



With the VSV for the vapor pressure sensor off, the PCM detects that there is no continuity between the sensor and the canister.
 
With the VSV for the vapor pressure sensor on, the PCM detects that there is no continuity between the sensor and the fuel tank.
 
After purge cutoff is enabled, the pressure in the charcoal canister is maintained at atmospheric pressure.
 

Understanding MIL Conditions

Several of the "on" or "off" conditions for the MIL are described next:



MIL Off all the time - This indicates the PCM did not detect any faults in the Emission system or the MIL circuit is faulty
 
MIL On all the time - This indicates the PCM detected a fault in an Emission system that could affect the emission levels
 
MIL Flashing - This indicates the PCM detected a fault in the Fuel system or a Misfire fault that could damage the catalytic converter
 

Actions Or Conditions To Turn Off The MIL

The PCM will turn off the MIL if any of these actions occur:



The codes are cleared with a Generic or Proprietary Scan Tool
 
Power to the PCM is removed (at the battery or the PCM fuse)
 
The vehicle is driven on three consecutive trips that include an OBD II Warmup Cycle and meets all code set conditions without detecting any emission-related faults
 

MIL Circuit Diagnosis

If the Malfunction Indicator Lamp (MIL) does not operate correctly, refer to the repair steps listed in the articles that follow to diagnose the MIL operation and the PCM.

MIL Condition: Light Flashes Once Per Second In KOER Mode

This condition indicates a fault in an emissions related system that could damage the vehicle catalyst. Use the Scan Tool to read the trouble codes and freeze frame data. Repair the misfire or fuel system fault. Then perform a PCM Reset and do the appropriate drive cycle.

MIL Condition: Light On For 2 Seconds, Then Goes Off At KOEO Mode

This is the normal operation of the PCM and MIL control circuit. This step can be used as a bulb check and initial check of PCM operation.

MIL Condition: MIL Does Not Come On For 2 Seconds - Engine Starts

This condition can be caused by any of these faults:



If this problem is intermittent in nature, check the fuse that provides power to the MIL for a loose connection or corrosion. Inspect condition of the MIL control circuit terminal at the PCM.
 
An open circuit between the MIL (lamp) and the PCM control circuit. Inspect the bulb connections and condition of the PCM terminals.
 
PCM is faulty (due to possible shorted MIL control driver circuit).
 
An open condition in the PCM battery or ignition power circuits.
 
An open or high resistance condition in the PCM ground circuits.
 

MIL Condition: MIL Does Not Come On For 2 Seconds - No Start Fault

This condition can be caused by several conditions - do these steps:



Turn the key off and remove the following connectors: the PCM connector that connects to these sensors: EGR gas temperature, fuel tank pressure sensor, MAP and Throttle Position.
 
Check for continuity to ground between the MAP sensor VREF and the other VREF circuits at the PCM to ground. If continuity exists, locate the short to ground in the VREF circuit and retest.
 

MIL Condition: MIL On With No Codes Stored In KOEO Or KOER Mode

This condition can be caused by any of these faults:



MIL control wire is shorted to ground between the lamp and the PCM.
 
The J1850 Bus + circuit to the DLC 16-P connector terminal No. 2 is shorted to ground. Turn the key off, remove the PCM connector and check terminal No. 2 in the DLC for continuity to ground.
 
PCM is faulty (due to possible shorted MIL control driver circuit).
 
An open condition in the PCM battery or ignition power circuits.
 
An open or high resistance condition in the PCM ground circuits.
 

Similar Conditions

If a fuel or misfire-related code sets, the vehicle must be driven under conditions similar to when the fault was detected before the PCM will de-activate the MIL. In effect, the vehicle must be driven within 375 RPM of the engine speed and engine load (10%) of the engine load value, and with engine temperature conditions similar to the temperature value stored in Freeze Frame data when the code set.

Trip Definition

An OBD II Trip is vehicle operation (following an engine off period) of such duration and driving modes that all components or systems are monitored at least once by the PCM diagnostics (except the catalyst).

OBD II Trip Definition



Malfunction Indicator Lamp

OBD II regulations (CARB and EPA) require that a Malfunction Indicator Lamp (MIL) be illuminated when a fault is detected, and that a Diagnostic Trouble Code (DTC) is stored in the PCM memory.



Click image to see an enlarged view

Fig.

Understanding MIL Conditions

Several of the "on" or "off" conditions for the MIL are described next:



MIL Off all the time - This indicates the PCM did not detect any faults in the Emission system or the MIL circuit is faulty
 
MIL On all the time - This indicates the PCM detected a fault in an Emission system that could affect the emission levels
 
MIL Flashing - This indicates the PCM detected a fault in the Fuel system or a Misfire fault that could damage the catalytic converter
 

Actions Or Conditions To Turn Off The MIL

The PCM will turn off the MIL if any of these actions occur:



The codes are cleared with a Generic or Proprietary Scan Tool
 
Power to the PCM is removed (at the battery or the PCM fuse)
 
The vehicle is driven on three consecutive trips that include an OBD II Warmup Cycle and meets all code set conditions without detecting any emission-related faults
 

Similar Conditions

If a fuel or misfire-related code sets, the vehicle must be driven under conditions similar to when the fault was detected before the PCM will de-activate the MIL. In effect, the vehicle must be driven within 375 RPM of the engine speed and engine load (10%) of the engine load value, and with engine temperature conditions similar to the temperature value stored in Freeze Frame data when the code set.

Trip Definition

An OBD II Trip is vehicle operation (following an engine off period) of such duration and driving modes that all components or systems are monitored at least once by the PCM diagnostics (except the catalyst).

OBD II Warm-up Cycle



Once a MIL is off, the trouble code will remain in memory until 40 warmup cycles are completed without the same fault reoccurring.

A warmup cycle is defined as a trip that includes a change in engine temperature of at least 40F, and where the engine tempe rature reaches at least 160F.



Click image to see an enlarged view

Fig.

DTC Numbering Explanation

The number in the hundredth position indicates the specific vehicle system or sub-group in which the failure occurred.



Click image to see an enlarged view

Fig.

This position should be consistent for P0xxx and P1xxx type codes.

An example of how to interpret an OBD II code is shown in the Graphic to the right.

The Society of Automotive Engineers (SAE) developed the numbers and systems in the list that follows:

P0100 - Air Metering and Fuel System fault

P0200 - Fuel System (fuel injector only) fault

P0300 - Ignition System or Misfire fault

P0400 - Emission Control System fault

P0500 - Idle Speed Control, Vehicle Speed Sensor fault

P0600 - Computer Output Circuit (relay, solenoid, etc.) fault

P0700 - Transaxle, Transmission faults

Note: The first and tenth digits indicate the type of Emission System that has failed.

 
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