codes never identify bad parts just failed systems.

what were the other codes??????

this is the chart for the code. no parts replacing till the failure is determined

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 45 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 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 Tools
MB991502: Scan Tool (MUT-II)

Answered by ASEMaster6371 (expert)
24,854 answers provided

the only code that was coming up when I had auto zone check it was the P1400 code. It is still the only code that is showing up. I was told by auto zone it could be a bad fuel pressure sensor that could be cousing the code but I don't see how?

Response from tman252s
2 questions asked