Fuel and Emissions Systems Acura MDX II

Scheme 175

Intermittent Failures

The term "intermittent failure" means a system may have had a failure, but it checks OK now. If the malfunction indicator lamp (MIL) on the dash does not come on, check for poor connections or loose pins at all connectors related to the circuit that you are troubleshooting. If the MIL was on but then went out, the original problem may have been intermittent.

Service Information

Some DTCs or symptoms can be caused by a combination of PCM software and specific driving habits. Periodically, new PCM software or new service procedures may become available. Always check on-line for the latest software or service information related to the DTCs or symptoms you are troubleshooting.

Opens and Shorts

"Open" and "short" are common electrical terms. An open is a break in a wire or at a connection. A short is an accidental connection of a wire to ground or to another wire. In simple electronics, this usually means something won't work at all. With complex electronics (such as PCMs) this can sometimes mean something works, but not the way it's supposed to.

How to Use the HDS (Honda Diagnostic System)

If the MIL (malfunction indicator lamp) has come on

Scheme 176

Scheme 177

1. Start the engine, and check the MIL (A). NOTE: If the ignition switch is turned ON (II), and the engine is not started, the MIL stays on for 15-20 seconds (see «HOW TO SET READINESS CODES»(/acura/mdx/ii-2006-2010/remont/testing-diagnostics/#fuel-and-emissions-systems) ).
2. If the MIL stays on, connect the HDS to the data link connector (DLC) (A) located under the driver's side of the dashboard.
3. Turn the ignition switch ON (II).
4. Make sure the HDS communicates with the PCM and other vehicle systems. If it doesn't, go to DLC circuit troubleshooting (see «DLC CIRCUIT TROUBLESHOOTING»(/acura/mdx/ii-2006-2010/remont/testing-diagnostics/#pgm-fi-system__dlc-circuit-troubleshooting) ).
5. Check the diagnostic trouble code (DTC) and note it. Also check the freeze data and/or on-board snapshot data, and download any data found. Then refer to the indicated DTCs troubleshooting, and begin the appropriate troubleshooting procedure. NOTE: Freeze data indicates the engine conditions when the first system malfunction, misfire, or fuel trim malfunction that activated the MIL was detected. The HDS can read the DTCs, freeze data, on-board snapshot, current data, and other powertrain control module (PCM) data. For specific operations, refer to the user's manual that came with the HDS.
6. If no DTCs are found, go to MIL circuit troubleshooting (see «MIL CIRCUIT TROUBLESHOOTING»(/acura/mdx/ii-2006-2010/remont/testing-diagnostics/#pgm-fi-system) ). If the MIL did not stay on If the MIL did not stay on but there is a driveability problem, do the symptom troubleshooting. If you can't duplicate the DTC Some of the troubleshooting requires you to reset the PCM and try to duplicate the DTC. If the problem is intermittent and you can't duplicate the code, do not continue through the procedure. To do so will only result in confusion and possibly, a needlessly replaced PCM.

HDS Clear Command

The PCM stores various specific data to correct the system even if there is no electrical power such as when the battery negative terminal is disconnected. Stored data based on failed parts should be cleared by using the "CLEAR COMMAND" of the HDS, if parts are replaced.

The HDS has three kinds of clear commands to meet this purpose. They are DTC clear, PCM reset, and crank (CKP) pattern clear. DTC clear command erases all stored DTC codes, freeze data, on-board snapshot, and readiness codes. This must be done with the HDS after reproducing the DTC during troubleshooting.

The PCM reset command erases all stored DTC codes, freeze data, on-board snapshot, readiness codes, and all specific data to correct the system except crank (CKP) pattern. If the crank (CKP) pattern data in the PCM was cleared, you must do the crank (CKP) pattern learn procedure. The crank (CKP) pattern clear command erases only crank (CKP) pattern data. This command is for repair of a misfire or the CKP sensor.

Scan Tool Clear Command

If you are using a generic scan tool to clear commands, be aware that there is only one setting for clearing the PCM, and it clears all commands at the same time (crank (CKP) pattern learn, idle learn, readiness codes, freeze data, on-board snapshot, and DTCs). After you clear all commands, you then need to do these procedures, in this order: PCM idle learn procedure (see PCM IDLE LEARN PROCEDURE ); crank (CKP) pattern learn procedure; Test-drive to set readiness codes to complete (see HOW TO SET READINESS CODES ).

DTC Clear

1. Clear the DTC with the HDS while the engine is stopped.
2. Turn the ignition switch OFF.
3. Turn the ignition switch ON (II), and wait 30 seconds.
4. Turn the ignition switch OFF, and disconnect the HDS from the DLC.

PCM Reset

1. Reset the PCM with the HDS while the engine is stopped.
2. Turn the ignition switch OFF.
3. Turn the ignition switch ON (II), and wait 30 seconds.
4. Turn the ignition switch OFF, and disconnect the HDS from the DLC.
5. Do the PCM idle learn procedure (see «PCM IDLE LEARN PROCEDURE»(/acura/mdx/ii-2006-2010/remont/engine-control-systems/#idle-control-system__pcm-idle-learn-procedure) ).

Scheme 178

1. Connect the HDS to the data link connector (DLC) (A) located under the driver's side of the dashboard.
2. Turn the ignition switch ON (II).
3. Make sure the HDS communicates with the PCM and other vehicle systems. If it doesn't, go to the DLC circuit troubleshooting (see «DLC CIRCUIT TROUBLESHOOTING»(/acura/mdx/ii-2006-2010/remont/testing-diagnostics/#pgm-fi-system__dlc-circuit-troubleshooting) ).
4. Select CRANK PATTERN in the ADJUSTMENT MENU with the HDS.
5. Select CRANK PATTERN LEARNING with the HDS, and follow the screen prompts.

Learn Procedure (without the HDS)

1. Start the engine. Hold the engine speed at 3,000 rpm without load (in Park or neutral) until the radiator fan comes on.
2. Test-drive the vehicle on a level road: Decelerate (with the throttle fully closed) from an engine speed of 2,500 rpm down to 1,000 rpm with the transmission in D position.
3. Test-drive the vehicle on a level road: Decelerate (with the throttle fully closed) from an engine speed of 5,000 rpm down to 3,000 rpm with the transmission in D position.
4. Repeat step 2 and 3 several times.
5. Turn the ignition switch OFF.
6. Turn the ignition switch ON (II), and wait 30 seconds.

How to End a Troubleshooting Session (required after any troubleshooting)

1. Reset the PCM with the HDS.
2. Do the PCM idle learn procedure (see «PCM IDLE LEARN PROCEDURE»(/acura/mdx/ii-2006-2010/remont/engine-control-systems/#idle-control-system__pcm-idle-learn-procedure) ).
3. Turn the ignition switch OFF.
4. Disconnect the HDS from the DLC. NOTE: The PCM is part of the immobilizer system. If you replace the PCM, it will have a different immobilizer code. In order for the engine to start, you must rewrite the immobilizer code with the HDS ( «IMMOBILIZER SYSTEM--MDX»(/acura/mdx/ii-2006-2010/remont/door-locks-anti-theft-systems/#immobilizer-system) article).

How to Troubleshoot Circuits at the PCM Connectors

Note. The PCM overwrites data and monitors the EVAP system for up to about 40 minutes after the ignition switch is turned OFF. Jumping the SCS line after turning the ignition switch OFF cancels this function. Disconnecting the PCM during this function, without jumping the SCS line first, can damage the PCM. PCM connectors A, B, and C have symbols (A=[] B=delta, C=o) embosed on them for identification.

Scheme 179

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Scheme 181

1. Jump the SCS line with the HDS.
2. Remove the bracket (D), then free the A/C discharge line (E) from the clip (F) and remove the A/C suction line mounting bracket bolt (G).
3. Remove the cover (H), then disconnect the PCM connector A, B, and C.
4. When diagnosis/troubleshooting is made at the PCM connector, use the measurement hole (A) above the terminal you need to check.
5. Connect one side of the patch cord (A) terminals to a commercially available digital multimeter (B), and connect the other side of the patch cord terminals to a commercially available banana jack (Pomona Electronics Tool No. 3563 or equivalent) (C).
6. Gently contact the pin probe (male) at the terminal test port from the terminal side. Do not force the tips into the terminals. NOTE: For accurate results, always use the pin probe (male). To prevent damage to the connector terminals, do not insert test equipment probes, paper clips, or other substitutes as they can damage the terminals. Damaged terminals cause a poor connection and an incorrect measurement. Do not puncture the insulation on a wire. Punctures can cause poor or intermittent electrical connections.

Substituting the PCM

Special Tools Required

1. Honda diagnostic system (HDS) tablet tester
2. Honda interface module (HIM) and an iN workstation with HDS and CM update software
3. HDS pocket tester
4. GNA600 and an iN workstation with HDS and CM update software

Note. Use this procedure when you need to substitute a known-good PCM during troubleshooting procedures.

Scheme 182

Scheme 183

1. Connect the HDS to the data link connector (DLC) (A) located under the driver's side of the dashboard.
2. Turn the ignition switch ON (II).
3. Make sure the HDS communicates with the PCM and other vehicle systems. If it doesn't, go to the DLC circuit troubleshooting (see «DLC CIRCUIT TROUBLESHOOTING»(/acura/mdx/ii-2006-2010/remont/testing-diagnostics/#pgm-fi-system__dlc-circuit-troubleshooting) ). If you are returning from DLC circuit troubleshooting, skip step 4 to 5 , then clean the throttle body after substituting the PCM (see «THROTTLE BODY CLEANING»(/acura/mdx/ii-2006-2010/remont/mechanical/#intake-air-system__throttle-body-cleaning) ).
4. USA, Canada models: Select the INSPECTION MENU with the HDS.
5. USA, Canada models: Select the ETCS TEST, then select the TP POSITION CHECK, and follow the screen prompts. NOTE: USA, Canada models: If the TP POSITION CHECK indicates FAILED, continue this procedure.
6. Turn the ignition switch OFF.
7. Jump the SCS line with the HDS.
8. Remove the bracket (D), then free the A/C discharge line (E) from the clip (F) and remove the A/C suction line mounting bracket bolt (G).
9. Remove the cover (H), then disconnect the PCM connectors A, B, and C. NOTE: PCM connectors A, B, and C have symbols (A=[], B=delta, C=o) embosed on them for identification.
10. Remove the bolts (I), then remove the PCM (J).
11. Install the parts in the reverse order of removal.
12. Open the SCS with the HDS.
13. Turn the ignition switch ON (II). NOTE: USA, Canada models: DTC P0630 "VIN Not Programmed or Mismatch" may be stored because the VIN has not been programmed into the PCM; ignore it, and continue this procedure.
14. USA, Canada models: Manually input the VIN to the PCM with the HDS.
15. Update the PCM if it does not have the latest software.
16. Select the IMMOBI SYSTEM with the HDS.
17. Enter the immobilizer code with the PCM replacement procedure in the HDS; it allows you to start the engine.
18. Reset the PCM with the HDS.
19. USA, Canada models: If the TP POSITION CHECK failed in step 6 , clean the throttle body (see «THROTTLE BODY CLEANING»(/acura/mdx/ii-2006-2010/remont/mechanical/#intake-air-system__throttle-body-cleaning) ).
20. Do the PCM idle learn procedure (see «PCM IDLE LEARN PROCEDURE»(/acura/mdx/ii-2006-2010/remont/engine-control-systems/#idle-control-system__pcm-idle-learn-procedure) ).
21. Do the CKP pattern learn procedure.

OBD Status

The OBD status shows the current system status of each DTC and all of the parameters. This function is used to see if the repair was successfully completed. The results of diagnostic tests for the DTC are displayed as

1. PASSED: The on board diagnosis is successfully finished.
2. FAILED: The on board diagnosis has finished but failed.
3. EXECUTING: The vehicle is in enable criteria conditions for the DTC and the on board diagnosis is running.
4. NOT COMPLETED: The on board diagnosis was running but is out of the enable conditions for the DTC.
5. OUT OF CONDITION: The vehicle has stayed out of the enable conditions for the DTC.

DTC Troubleshooting Index

DTC TROUBLESHOOTING CHART

Symptom Troubleshooting Index

When the vehicle has one of these symptoms, check for a diagnostic trouble code (DTC) with the HDS. If there is no DTC, do the diagnostic procedure for the symptom, in the sequence listed, until you find the cause.

SYMPTOM TROUBLESHOOTING CHART

Electronic Control System

The functions of the fuel and emission control systems are managed by the powertrain control module (PCM).

Self-diagnosis

The PCM detects a signal failure from a sensor or from another control unit and stores a Temporary DTC or a DTC. Depending on the failure, a DTC is stored in either the first or the second drive cycle (for DTC P0457, the DTC is set in the beginning of the third drive cycle). When a DTC is stored, the PCM turns on the malfunction indicator lamp (MIL) by sending a signal to the gauge via F-CAN.

1. One Drive Cycle Detection Method When an abnormality occurs in the signal from a sensor or from another control unit, the PCM stores a DTC for the failure and turns on the MIL immediately.
2. Two Drive Cycle Detection Method When an abnormality occurs in the signal from a sensor or from another control unit in the first drive cycle, the PCM stores a Temporary DTC for the failure. The MIL does not come on at this time. If the failure continues in the second drive cycle, the PCM stores a DTC and turns on the MIL.

Fail-safe Function

When an abnormality occurs in the signal from a sensor or from another control unit, the PCM ignores that signal and substitutes a pre-programmed value that allows the engine to continue running. This causes a DTC to be stored and the MIL to come on.

MIL Bulb Check and Readiness Code Condition

When the ignition switch is turns ON (II), the PCM turns on the MIL via the F-CAN circuit for about 15 to 20 seconds to check the bulb condition. If any readiness codes are not set to complete, the MIL flashes five times. If all readiness codes are set to complete, the MIL goes off.

Self Shut Down (SSD) Mode

After the ignition switch is turned OFF, the PCM stays on (up to 40 minutes). If the PCM connector is disconnected during this time, the PCM may be damaged. To cancel this mode, disconnect the negative cable from the battery or jump the SCS line with the HDS after the ignition switch is turned OFF.

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Note. Standard battery voltage is about 12 V.

VOLTAGE REFERENCE CHART

Scheme 193

Note. Standard battery voltage is about 12 V.

VOLTAGE REFERENCE CHART

Scheme 194

Note. Standard battery voltage is about 12 V.

VOLTAGE REFERENCE CHART

Scheme 195

Note. Standard battery voltage is about 12 V.

VOLTAGE REFERENCE CHART

Scheme 196

Note. Standard battery voltage is about 12 V.

VOLTAGE REFERENCE CHART

Scheme 197

Note. Standard battery voltage is about 12 V.

VOLTAGE REFERENCE CHART

Scheme 198

Note. Standard battery voltage is about 12 V.

VOLTAGE REFERENCE CHART

Scheme 199

Note. Standard battery voltage is about 12 V.

VOLTAGE REFERENCE CHART

Scheme 200

Note. Standard battery voltage is about 12 V.

VOLTAGE REFERENCE CHART

Scheme 201

Note. Standard battery voltage is about 12 V.

VOLTAGE REFERENCE CHART

Scheme 202

Note. Standard battery voltage is about 12 V.

VOLTAGE REFERENCE CHART

Scheme 203

Note. Standard battery voltage is about 12 V.

VOLTAGE REFERENCE CHART

Scheme 204

Note. Standard battery voltage is about 12 V.

VOLTAGE REFERENCE CHART

Scheme 205

Note. Standard battery voltage is about 12 V.

VOLTAGE REFERENCE CHART

Scheme 206

Note. Standard battery voltage is about 12 V.

VOLTAGE REFERENCE CHART

Scheme 207

Note. Standard battery voltage is about 12 V.

VOLTAGE REFERENCE CHART

Scheme 208

Note. Standard battery voltage is about 12 V.

VOLTAGE REFERENCE CHART

PGM-FI System

The programmed fuel injection (PGM-FI) system is a sequential multiport fuel injection system.

Alternator Control

The alternator signals the PCM during charging.

Air Conditioning (A/C) Compressor Clutch Relay

When the PCM receives a demand for cooling from the A/C system, it delays the compressor from being energized, and enriches the mixture to assure smooth transition to the A/C mode.

Air Fuel Ratio (A/F) Sensor

The A/F sensor operates over a wide air/fuel range. The A/F sensor is installed upstream of the warm up the three way catalytic converter (WU-TWC), and sends signals to the PCM which varies the duration of fuel injection accordingly.

Scheme 209

Barometric Pressure (BARO) Sensor

The BARO sensor is inside the PCM. It converts atmospheric pressure into a voltage signal that moddifies the basic duration of the fuel injection discharge.

Camshaft Position (CMP) Sensor

The CMP sensor input is used by the PCM to determine ignition timing at start up (cranking) and when crank angle is abnormal.

Scheme 210

Crankshaft Position (CKP) Sensor

The CKP sensor detects crankshaft speed and is used by the PCM to determine ignition timing and timing for fuel injection of each cylinder, as well as detecting engine misfire.

Scheme 211

Engine Coolant Temperature (ECT) Sensor 1 and 2

ECT sensors 1 and 2 are temperature dependent resistors (thermistors). The resistance decreases as the engine coolant temperature increases.

Scheme 212

Ignition Timing Control

The PCM contains the memory for basic ignition timing at various engine speeds and manifold absolute pressures. It also adjusts the timing according to engine coolant temperature.

Injector Timing and Duration

The PCM contains the memory for basic discharge duration at various engine speeds and manifold pressures. The basic discharge duration, after being read out from the memory, is further modified by signals sent from various sensors to obtain the final discharge duration.

By monitoring long term fuel trim, the PCM detects long term malfunctions in the fuel system and sets a diagnostic trouble code (DTC).

Knock Sensor

The knock control system adjusts the ignition timing to minimize knock.

Scheme 213

Malfunction Indicator Lamp (MIL) Indication (In relation to Readiness Codes)

The vehicle has certain "readiness codes" that are part of the on-board diagnostics for the emissions systems. If the vehicle's battery has been disconnected or gone dead, if the DTCs have been cleared, or if the PCM has been reset, these codes are reset. In some states, part of the emissions testing is to make sure these codes are set to complete. If all of them are not set to complete, the vehicle may fail the test, or the test cannot be finished.

To check if the readiness codes are set to complete, turn the ignition switch ON (II), but do not start the engine. The MIL will come on for 15-20 seconds. If it then goes off, the readiness codes are complete. If it flashes five times, one or more readiness codes are not complete. To set each code, drive the vehicle or run the engine as described in the procedures (see HOW TO SET READINESS CODES ).

Manifold Absolute Pressure (MAP) Sensor

The MAP sensor converts manifold absolute pressures into electrical signals to the PCM.

Scheme 214

Mass Air Flow (MAF) Sensor/Intake Air Temperature (IAT) Sensor

The mass airflow (MAF) sensor/intake air temperature (IAT) sensor contains a hot wire and a thermistor. It is located in the intake air passage. The resistance of the hot wire and thermistor change due to intake air temperature and airflow. The control circuit in the MAF sensor controls the current to keep the hot wire at a set temperature. The current is converted to voltage in the control circuit, then output to the PCM.

Scheme 215

Output Shaft (Countershaft) Speed Sensor

This sensor detects countershaft speed.

Scheme 216

Secondary Heated Oxygen Sensor (Secondary HO2S)

The secondary HO2S detects the oxygen content in the exhaust gas downstream of the warm up three way catalytic converter (WU-TWC), and sends signals to the PCM. To stabilize its output, the sensor has an internal heater. The PCM compares the HO2S output with the A/F sensor output to determine catalyst efficiency. The secondary HO2S is on the WU-TWC.

Scheme 217

Electronic Throttle Control System

The throttle is electronically controlled by the electronic throttle control system. Refer to the system diagram to see a functional layout of the system.

Idle control: When the engine is idling, the PCM controls the throttle actuator to maintain the proper idle speed according to engine loads.

Acceleration control: When the accelerator pedal is pressed, the PCM opens the throttle valve depending on the accelerator pedal position (APP) sensor signal.

Cruise control: The PCM controls the throttle actuator to maintain the set speed when cruise control is operating. The throttle actuator takes the place of the cruise control actuator.

Accelerator Pedal Position (APP) Sensor

As the accelerator pedal position changes, the sensor varies the signal voltage to the PCM.

Scheme 218

Throttle Body

The throttle body is a single-barrel side draft type. The lower portion of the throttle valve is heated by engine coolant from the cylinder head to prevent icing of the throttle plate.

Scheme 219

Idle Control System

When the engine is cold, the A/C compressor is on, the transmission is in gear, the brake pedal is pressed, the power steering load is high, or the alternator is charging, the PCM sends signals to the throttle actuator to maintain the correct idle speed.

Brake Pedal Position Switch

The brake pedal position switch signals the PCM when the brake pedal is pressed.

Power Steering Pressure (PSP) Switch

The PSP switch signals the PCM when the power steering load is high.

Fuel Cutoff Control

During deceleration with the throttle valve closed, current to the injectors is cut off to improve fuel economy at engine speeds over 850 rpm. Fuel cutoff control also occurs when the engine speed exceeds 6,600 rpm, regardless of the position of the throttle valve, to protect the engine from over-revving. When the vehicle is stopped, the PCM cuts the fuel at engine speeds over 5,000 rpm. On a cold engine, fuel cut occurs at a lower engine speed.

Fuel Pump Control

When the ignition switch is turned on, the PCM grounds PGM-FI main relay 2 which feeds current to the fuel pump control module. The PCM sends a signal to the fuel pump control module to operate the fuel pump for 2 seconds to pressurize the fuel system. With the engine running, the fuel pump speed is controlled in four levels by the fuel pump control module. The PCM decides the fuel pump speed by the calculation of the injector activation time and engine speed and sends a operation command signal to the fuel pump control module. This operation made possible to decrease fuel pump noise at low engine speed.

PGM-FI Main Relay 1 and 2

PGM-FI main relay 1 is energized whenever the ignition switch is ON (II) to supply battery voltage to the PCM, power to the injectors, and power for PGM-FI main relay 2. PGM-FI main relay 2 is energized to supply power to the fuel pump (fuel pump control module) for 2 seconds when the ignition switch is turned ON (II), and when the engine is cranking or running.

Catalytic Converter System

Warm Up/Three Way Catalytic Converter (WU-TWC) and Under-Floor Three Way Catalytic Converter (TWC)

The WU-TWC/TWC converts hydrocarbons (HC), carbon monoxide (CO), and oxides of nitrogen (NOx) in the exhaust gas to carbon dioxide (CO2), nitrogen (N2), and water vapor.

WU-TWC

Scheme 220

Exhaust Gas Recirculation (EGR) System

Refer to the system diagram to see a functional layout of the system.

EGR Valve

The EGR valve lowers peak combustion temperatures and reduces oxides of nitrogen emissions (NOx) by recirculating exhaust gas through the intake manifold and into the combustion chambers.

Positive Crankcase Ventilation (PCV) System

The PCV valve prevents blow-by gasses from escaping into the atmosphere by venting them into the intake manifold.

Scheme 221

Evaporative Emission (EVAP) Control System

Refer to the system diagram to see a functional layout of the system.

EVAP Canister

The EVAP canister temporarily stores fuel vapor from the fuel tank until it can be purged back into the engine and burned.

EVAP Canister Purge Valve

When the engine coolant temperature is below 140°F (60°C), the PCM turns off the EVAP canister purge valve which cuts vacuum to the EVAP canister.

Scheme 222

Fuel Tank Pressure (FTP) Sensor

The FTP sensor converts fuel tank absolute pressure into an electrical input to the PCM.

Scheme 223

EVAP Canister Vent Shut Valve

The EVAP canister vent shut valve is on the EVAP canister.

The EVAP canister vent shut valve controls the venting of the EVAP canister.

Scheme 224

Fuel Cap Warning Message

The PCM detects a loose or missing fuel fill cap as an evaporative system leak and alerts the driver by showing a warning message in the multi-information display.

First drive cycle

The first time a leak is detected a "TIGHTEN FUEL CAP" message appears in the multi-information display (A). To scroll to another message, press the select/reset button. The "TIGHTEN FUEL CAP" message will appear each time you restart the engine until the system turns the message off. Turn the engine off then replace or tighten the fuel fill cap until it clicks at least once.

Scheme 225

Procedure

1. Tighten the fuel fill cap until it clicks.
2. Clear the Temporary DTC with the HDS.
3. Verify there is no leak by doing the EVAP FUNCTION TEST in the INSPECTION MENU with the HDS.

1. Tighten the fuel fill cap until it clicks.
2. Start the engine, then turn the ignition switch OFF.
3. Repeat step 2 two more times.

Electronic Throttle Control System Diagram

The electronic throttle control system consists of the throttle actuator, throttle position (TP) sensor A/B, accelerator pedal position (APP) sensor A/B, the electronic throttle control system (ETCS) control relay, and the PCM.

Scheme 226

Intake Manifold Tuning (IMT) Valve System

Engine power is adjusted by opening and closing the intake manifold tuning (IMT) actuator. When the valve is closed, there is high torque at low engine speed. When the valve is open, there is high torque at high engine speed.

The intake manifold tuning (IMT) valve actuator contains a sensor that detects the IMT valve position and sends it to the PCM.

Scheme 227

Exhaust Gas Recirculation (EGR) System Diagram

The EGR system reduces oxides of nitrogen (NOx) emissions by recirculating exhaust gas through the EGR valve and the intake manifold into the combustion chambers. The PCM memory contains the ideal EGR valve position for various operating conditions.

The EGR valve position sensor detects the amount of EGR valve lift, and sends it to the PCM. The PCM then compares it with the ideal lift in its memory (based on signals sent from other sensors). If there is any difference between the two, the PCM cuts current to the EGR valve.

Scheme 228

Evaporative Emission (EVAP) Control Diagram

The EVAP controls minimize the amount of fuel vapor escaping to the atmosphere. Vapor from the fuel tank is temporarily stored in the EVAP canister until it can be purged from the canister into the engine and burned.

Scheme 229

1. The EVAP canister is purged by drawing fresh air through it and into a port on the intake manifold. The purging vacuum is controlled by the EVAP canister purge valve, which operates whenever engine coolant temperature is above 140°F (60°C).
2. During refueling, the fuel tank vapor control valve opens with the pressure in the fuel tank, and feeds the fuel vapor to the EVAP canister.

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Malfunction Indicator Lamp (MIL) Indication (In relation to Readiness Codes)

The vehicle has certain "readiness codes" that are part of the on-board diagnostics for the emissions systems. If the vehicle's battery has been disconnected or gone dead, if the DTCs have been cleared, or if the PCM has been reset, these readiness codes are reset to incomplete. In some states, part of the emissions testing is to make sure these codes are set to complete. If all of them are not set to complete, the vehicle may fail the emission test, or the test cannot be finished.

To check if the readiness codes are set to complete, turn the ignition switch ON (II), but do not start the engine. The MIL will come on for 15-20 seconds. If it then goes off, the readiness codes are set to complete. If it flashes five times, one or more readiness codes are not set to complete. To set readiness codes from incomplete to complete, do the procedure for the appropriate code.

To check the status of a specific DTC system, check the OBD status in the DTC MENU with the HDS (see OBD STATUS ). This screen displays the code, the current data list of the enable criteria, and the status of the readiness testing.

Catalytic Converter Monitor and Readiness Code

Note. Do not turn the ignition switch off during the procedure. All readiness codes are cleared when the battery is disconnected, if the DTCs have been cleared, or if the PCM is reset with the HDS. Low ambient temperatures or excessive stop-and-go traffic may increase the drive time needed to switch the readiness code from incomplete to complete. The readiness code will not switch to complete until all the enable criteria are met. If a fault in the secondary HO2S system caused the MIL to come on, the readiness code cannot be set to complete until you correct the fault.

Enable Criteria

1. ECT SENSOR 1 at 158°F (70°C) or more.
2. IAT SENSOR at 20°F (-7°C) or more.
3. VSS above 25 mph (40 km/h).

1. Connect the HDS to the vehicle's data link connector (DLC), and bring up the READINESS CODEs screen for Catalyst in the DTCs MENU.
2. Start the engine.
3. Test-drive the vehicle under stop-and-go conditions with short periods of steady cruise. After about 5 miles (8 km), the readiness code should switch to complete.
4. If the readiness code is still not set to complete, check for a Temporary DTC with the HDS. If there is no DTC, one or more of the enable criteria were probably not met; repeat the procedure.

Evaporative Emission (EVAP) Control System Monitor and Readiness Code

Note. All readiness codes are cleared when the battery is disconnected, if the DTCs have been cleared, or if the PCM is reset with the HDS.

1. Battery voltage is more than 10.5 V.
2. Engine at idle.
3. ECT SENSOR 1 and SENSOR 2 between 176°F (80°C) and 212°F (100°C).
4. MAP sensor less than 46.6 kPa (14 in.Hg, 350 mmHg).
5. VSS 0 mph (0 km/h).
6. IAT SENSOR between 32°F (0°C) and 212°F (100°C).

1. Connect the HDS to the DLC.
2. Start the engine.
3. Select EVAP TEST in the INSPECTION MENU with the HDS, then select the FUNCTION TEST in the EVAP TEST MENU. If the result is normal, readiness is complete. If the result is not normal, go to the next step.
4. Check for a Temporary DTC. If there is no DTC, one or more of the enable criteria were probably not met; repeat the procedure.

Air Fuel Ratio (A/F) Sensor Monitor and Readiness Code

Note. Do not turn the ignition switch off during the procedure. All readiness codes are cleared when the battery is disconnected, if the DTCs have been cleared, or if the PCM is reset with the HDS.

ECT SENSOR 1 at 140°F (60°C) or more.

1. Start the engine.
2. Test-drive the vehicle under stop-and-go conditions with short periods of steady cruise. During the drive, decelerate (with the throttle fully closed) for 5 seconds. After about 3.5 miles (5.6 km), the readiness code should switch from incomplete to complete.
3. Check the readiness codes screen for the AIR FUEL RATIO (A/F) SENSOR in the DTCs MENU with the HDS. If the screen shows complete, readiness is complete. If the screen shows not complete, go to the next step.
4. Check for a Temporary DTC. If there is no DTC, the enable criteria was probably not met. Select the DATA LIST MENU. Check the ECT SENSOR 1 in the ALL DATA LIST with the HDS. If the ECT SENSOR 1 is less than 140°F (60°C), run the engine until it is more than 140°F (60°C), then repeat the procedure.

Air Fuel Ratio (A/F) Sensor Heater Monitor Readiness Code

Note. All readiness codes are cleared when the battery is disconnected, if the DTCs have been cleared, or if the PCM is reset with the HDS.

1. Start the engine, and let it idle for 1 minute. The readiness code should switch from incomplete to complete.
2. If the readiness code is still not set to complete, check for a Temporary DTC. If there is no DTC, repeat the procedure.

Misfire Monitor and Readiness Code

1. This readiness code is always set to available because misfiring is continuously monitored.
2. Monitoring pauses, and the misfire counter resets, if the vehicle is driven over a rough road.
3. Monitoring also pauses, and the misfire counter holds at its current value, if the throttle position changes more than a predetermined value, or if driving conditions fall outside the range of any related enable criteria.

Fuel System Monitor and Readiness Code

1. This readiness code is always set to available because the fuel system is continuously monitored during closed loop operation.
2. Monitoring pauses when the catalytic converter, EVAP control system, and A/F sensor monitors are active.
3. Monitoring also pauses when any related enable criteria are not being met. Monitoring resumes when the enable criteria is again being met.

Comprehensive Component Monitor and Readiness Code

This readiness code is always set to available because the comprehensive component monitor is continuously running whenever the engine is cranking or running.

EGR Monitor and Readiness Code

Note. Do not turn the ignition switch off during the procedure. All readiness codes are cleared when the battery is disconnected, if the DTCs have been cleared, or if the PCM is reset with the HDS.

ECT SENSOR 1 at 176°F (80°C) or more.

1. Connect the HDS to the DLC.
2. Start the engine.
3. Drive at a steady speed with the transmission in D position, at 50-62 mph (80-100 km/h) or above for more than 10 seconds.
4. With the transmission in D position, decelerate from 62 mph (100 km/h) or above by completely releasing the throttle for at least 5 seconds. If the engine is stopped during this procedure, go to step 3 and do the procedure again.
5. Check the OBD status screen for DTC P0401 in the DTCs MENU with the HDS. If it is passed, readiness is complete. If it is not passed, go to step 3 and retest.

See also:
• DLC CIRCUIT TROUBLESHOOTING
• MIL CIRCUIT TROUBLESHOOTING
• PCM IDLE LEARN PROCEDURE
• IMMOBILIZER SYSTEM--MDX
• THROTTLE BODY CLEANING
• P0101 (50)
• P0102 (50)
• P0103 (50)
• P0107 (3)
• P0108 (3)
• P0111 (10)
• P0112 (10)
• P0113 (10)
• P0116 (86)
• P0117 (6)
• P0118 (6)
• P0122 (7)
• P0123 (7)
• P0125 (86)
• P0128 (87)
• P0133 (157)
• P0134 (151)
• P0135 (151)
• P0137 (161)
• P0138 (161)
• P0139 (161)
• P0141 (163)
• P0171 (153)
• P0222 (7)
• P0223 (7)
• P0300 (77)
• P0301 (71)
• P0325 (23)
• P0335 (4)
• P0339 (4)
• P0340 (9)
• P0344 (9)
• P0401 (80)
• P0404 (12)
• P0406 (12)
• P0420 (165)
• P0443 (92)
• P0451 (91)
• P0452 (91)
• P0453 (91)
• P0455 (90)
• P0461 (121)
• P0462 (121)
• P0463 (121)
• P0498 (117)
• P0499 (117)
• P0506 (14)
• P050A (167)
• P050B (167)
• P0562 (34)
• P0563 (34)
• P0602 (196)
• P060A (131)
• P0615 (198)
• P0627 (169)
• P062F (131)
• P0630 (139)
• P0685 (135)
• P1077 (106)
• P1078 (106)
• P1109 (13)
• P1116 (86)
• P1128 (5)
• P1129 (5)
• P1172 (157)
• P1297 (20)
• P1298 (20)
• P1454 (91)
• P1549 (34)
• P1658 (40)
• P1659 (40)
• P1683 (40)
• P1684 (40)
• P16BB (116)
• P16BC (116)
• P16BD (198)
• P16BE (198)
• P16BF (198)
• P2101 (40)
• P2118 (40)
• P2122 (37)
• P2123 (37)
• P2127 (37)
• P2128 (37)
• P2135 (7)
• P2138 (37)
• P2176 (40)
• P2183 (192)
• P2184 (192)
• P2185 (192)
• P2195 (155)
• P2227 (13)
• P2228 (13)
• P2229 (13)
• P2237 (155)
• P2238 (155)
• P2243 (155)
• P2245 (155)
• P2251 (155)
• P2252 (155)
• P2270 (161)
• P2279 (109)
• P2413 (12)
• P2610 (132)
• P2646 (22)
• P2647 (22)
• P2648 (21)
• P2649 (21)
• P2A00 (157)
• U0028 (126)
• U0114 (126)
• U0122 (126)
• U0155 (126)
• BATTERY TEST
• STARTER PERFORMANCE TEST
• FUEL PRESSURE TEST
• SYSTEM CHECK
• IDLE SPEED INSPECTION
• THROTTLE BODY TEST
• APP SENSOR SIGNAL INSPECTION
• FUEL TANK REPLACEMENT
• FUEL CAP WARNING MESSAGE SYSTEM TROUBLESHOOTING
• HOW TO SET READINESS CODES
• OBD STATUS