P1400

Manifold Differential Pressure Sensor Circuit:

CIRCUIT OPERATION
- A 5-volt voltage is applied on the manifold differential pressure sensor power terminal (terminal 3) from the PCM (terminal 46). The ground terminal (terminal 2) is grounded with the PCM (terminal 57).
- A voltage proportional to the pressure in the intake manifold plenum is sent from the manifold differential pressure sensor output terminal (terminal 1) to the PCM (terminal 91).

TECHNICAL DESCRIPTION
- The manifold differential pressure sensor outputs a voltage which corresponds to the negative pressure in the intake manifold.
- The PCM checks whether the voltage output by manifold differential pressure sensor is within a specified range.

DTC SET CONDITIONS

Check Conditions
- Eight minutes or more have passed after starting the engine. Note that this is only if the engine coolant temperature is less than 0 °C (32 °F) when starting.
- Engine coolant temperature is higher than 45 °C (113 °F).
- Intake air temperature is higher than 5 °C (41 °F).
- Volumetric efficiency is between 30 and 55 percent.

Judgment Criteria
- Manifold differential pressure sensor output voltage has continued to be higher than 4.6 volts [corresponding to an absolute pressure of 118 kPa (17 psi) or higher] for 2 seconds.

or

- Manifold differential pressure sensor output voltage has continued to be lower than 0.1 volt [corresponding to an absolute pressure of 2.4 kPa (0.3 psi) or lower] for 2 seconds.

Check Conditions
- Eight minutes or more have passed after starting the engine. Note that this is only if the engine coolant temperature is 0 °C (32 °F) or more when starting.
- Engine coolant temperature is higher than 45 °C (113 °F).
- Intake air temperature is higher than 5 °C (41 °F).
- Volumetric efficiency is lower than 30 percent.

Judgment Criteria
- Manifold differential pressure sensor output voltage has continued to be higher than 4.2 volts [corresponding to an absolute pressure of 108 kPa (16 psi) or higher] for 2 seconds.

Check Conditions
- Eight minutes or more have passed after starting the engine. Note that this is only if the engine coolant temperature is 0 °C (32 °F) or more when starting.
- Engine coolant temperature is higher than 45 °C (113 °F).
- Intake air temperature is higher than 5 °C (41 °F).
- Volumetric efficiency is higher than 70 percent.

Judgment Criteria
- Manifold differential pressure sensor output voltage has continued to be lower than 1.8 volts [corresponding to an absolute pressure of 46 kPa (4.6 psi) or lower] for 2 seconds.

TROUBLESHOOTING HINTS
The most likely causes for this code to be set are:
- Manifold differential pressure sensor failed.
- Open or shorted manifold differential pressure sensor circuit, or loose connector.
- PCM failed.

DIAGNOSIS
Required Special Tool:
MB991502: Scan Tool (MUT-II)

CAUTION: To prevent damage to scan tool MB991502, always turn the ignition switch to "LOCK" (OFF) position before connecting or disconnecting scan tool MB991502.




STEP 1. Using scan tool MB991502, check data list item 95: Manifold Differential Pressure Sensor.
1. Connect scan tool MB991502 to the data link connector.
2. Start the engine and run at idle.
3. Set scan tool MB991502 to the data reading mode for item 95, Manifold Differential Pressure Sensor.
- While engine is idling, pressure should be between 22.6 and 36.0 kPa.

If not within specifications, go to Step 2.

If within specifications, this malfunction is intermittent. Refer to How to Use Troubleshooting/Inspection Service Points - How to Cope with Intermittent Malfunction.




STEP 2. Check the circuits at the manifold differential pressure sensor connector B-18.
1. Disconnect connector B-18 and measure at the harness side.
2. Turn the ignition switch to "ON" position.
3. Measure voltage between terminal 3 and ground.
- Voltage should be between 4.8 and 5.2 volts.

4. Turn the ignition switch to "LOCK" (OFF) position.




5. Check for continuity between terminal 2 and ground.
- Should be less than 2 Ohms.

If the checks above meet the specification, go to Step 3.

If the checks above do not meet the specification, go to Step 5.




STEP 3. Check the output line at manifold differential pressure sensor connector B-18.
1. Disconnect connector B-18 and connect test harness special tool, MB991348, in between.
2. Start the engine and run at idle.
3. Measure voltage between terminal 1 and ground.

Standard value: 0.8 - 2.4 V

4. Turn the ignition switch to "LOCK" (OFF) position.

If within specifications, go to Step 4.

If not within specifications, replace the manifold differential pressure sensor.

Then go to Step 7.




STEP 4. Check harness connector B-18 at the manifold differential pressure sensor for damage.
If harness connector B-18 is normal, replace the manifold differential pressure sensor. Then go to Step 5.

If harness connector B-18 is damaged, repair or replace it. Refer to Harness Connector Inspection. Then go to Step 7.




STEP 5. Check harness connectors C-40, C-41 at the PCM for damage.
If harness connectors C-40, C-41 are damaged, repair or replace it. Refer to Harness Connector Inspection. Then go to Step 7.

If harness connectors C-40, C-41 are in good condition, go to Step 6.







STEP 6. Check the harness wire between the manifold differential pressure sensor connector B-18 and the PCM connectors C-40, C-41.
If the wire between the manifold differential pressure sensor connector B-18 and the PCM connectors C-40, C-41 are not damaged, replace the PCM. Then go to Step 7.

If the wire between the manifold differential pressure sensor connector B-18 and the PCM connectors C-40, C-41 are damaged, repair it. Then go to Step 7.

STEP 7. Test the OBD-II drive cycle
1. Carry out a test drive with the drive cycle pattern. Refer to Procedure 6 - Other Monitor.
2. Read the diagnostic trouble code, and confirm that a diagnostic trouble code P1400 does not reset.