How to fixt exhaust recirculation gas flow - 1998 Mazda Protege

DTC P0402: Exhaust Gas Recirculation (EGR) Flow Excessive

The engine control module (ECM) tests the exhaust gas recirculation (EGR) flow when the EGR is in operation. EGR desired flow is compared to EGR actual flow. If EGR flow is higher than expected DTC P0402 will set.

Do you know what EGR is ?

The fault is somewhere around the EGR valve - probably the EGR valve or the throttle position sensor.

Before replacing any sensors try removing and cleaning the EGR.

Here's a Youtube link that may be of help to you:

1999 maxima egr Google Search

This link explains about the EGR:
P0400 Exhaust Gas Recirculation Flow Malfunction

CEL code P0400 EGR Flow Malfunction

P1405 Exhaust Gas Recirculation System Valve 3

exhaust gas recirculation valve

replace egr valv and reset computer

What code ? are a few different ones for EGR valve > Low & high circuit voltage , testing circuits , PCM testing etc.... no code tells you to replace the EGR valve without testing . Your best bet , take it to a qualified repair shop.
DTC P0401 Exhaust Gas Recirculation (EGR) Flow Insufficient
DTC P0403 Exhaust Gas Recirculation (EGR) Solenoid Control Circuit
DTC P0404 Exhaust Gas Recirculation (EGR) Open Position Performance
DTC P0405 Exhaust Gas Recirculation (EGR) Position Sensor Circuit Low Voltage

The Exhaust Gas Recirculation (EGR) system is used to reduce Oxides of Nitrogen (NOx) in the engine exhaust. This is accomplished by allowing a predetermined amount of hot exhaust gas to recirculate and dilute the incoming air and fuel mixture. This process reduces peak flame temperature during combustion. The system uses a vacuum-controlled Exhaust Gas Recirculation (EGR) valve, in order to modulate exhaust gas flow from the exhaust manifold into the intake manifold.

i hope this helps you
plz vote comment if need more help reply

P1400 Exhaust Gas Recirculation valve position sensor
P1401 Exhaust Gas Recirculation valve position sensor
P1402 Exhaust Gas Recirculation metering orifice restricted
P1403 Exhaust Gas Recirculation differential pressure sensor
P1404 EGR Temperature Sensor circuit
P1405 Exhaust Gas Recirculation Differential Pressure Feedback Sensor upstream hose off or plugged
P1406 Exhaust Gas Recirculation Differential Pressure Feedback Sensor downstream hose off or plugged
P1407 EGR solenoid -No Flow Detected
P1408 EGR solenoid -Flow out of Self- Test Range
P1409 EGR Vacuum Regulator solenoid circuit malfunction
---
The sensor for the EGR Valve position is not functioning correctly.

p0401
Exhaust gas recirculation-insufficient flow detected
p0403
Exhaust gas recirculation-circuit malfunction
p0405
Exhaust gas recirculation vave position sensor A- circuit low

hope this helps. not sure where they are located

the EGR is exhaust gas recirculation valve,,what it does it when your driving it open and recirculates some exhuast fumes and shoots them back into to the intake so they get burn again and you get better gas mileage and low emmission from this,but if it has insufficent flow it means you need a new egr valve,,,they are expensive litte thing $200 or so just for the part

P0400 = EGR Flow
P0325 = knock sensor (Do not ever change a knock sensor, they don't affect anything and cost $600 to replace for absolutely no gain)
P1200 = I can't find this one. I think it's injector flow
report back on what you find.
Egr flow may be plugged egr passages or a bad solenoid.
--------------
1996 PCED OBDII-Villager SECTION 1B: Description and Operation
Exhaust Gas Recirculation System
Exhaust Gas Recirculation (EGR) System Operation The exhaust gas recirculation (EGR) system (Figure 1 below) recirculates a portion of the exhaust gases into the intake manifold under average vehicle driving conditions to reduce combustion temperatures and exhaust gas NOx content. The amount of exhaust gas recirculated varies according to operating conditions and will be cut completely under:

• Engine starting condition
• Low engine coolant temperature condition
• Excessively high engine coolant temperature condition
• Engine idling condition
• High engine speed condition
• Mass air flow sensor failure

The exhaust gas recirculation (EGR) system on the Villager uses the exhaust gas recirculation/evaporative emission (EGR/EVAP) control solenoid valve to provide vacuum to both the EGR valve and the EVAP canister when commanded by the PCM. If the exhaust backpressure is sufficient to close the EGR backpressure transducer valve, vacuum is sent to the EGR valve and allows EGR gas to flow into the intake manifold. If the exhaust backpressure is not sufficient, the EGR backpressure transducer will remain open and allow vacuum from the EGR/EVAP control solenoid to vent to the atmosphere.
The EGR system monitor, for OBD II regulations, uses an EGR temperature sensor to monitor the EGR system. The EGR temperature sensor is a thermister located in the EGR passageway. When hot exhaust gas is recirculated into the engine, the temperature at the EGR passageway increases. This increase is sensed by the EGR temperature sensor and a signal is sent to the PCM to indicate EGR flow. If the EGR temperature sensor does not detect EGR flow when commanded by the PCM after two consecutive drive cycles, the malfunction indicator lamp (MIL) will be illuminated and a diagnostic trouble code (DTC) will be stored. The MIL will be turned off after three consecutive drive cycles are completed with no malfunctions detected. The DTC will remain stored in the PCM memory until 80 drive cycles have been completed without the same malfunction detected in the system.
Figure 1: Exhaust Gas Recirculation (EGR) System Diagram Item Number Description 1 — EGR/EVAP Control Solenoid 2 — Air Cleaner Housing 3 — Throttle Valve 4 — EGR Temperature Sensor 5 — EGR Valve 6 — EGR Backpressure Transducer 7 — EVAP Canister
Exhaust Gas Recirculation (EGR) Backpressure Transducer Valve The exhaust gas recirculation (EGR) backpressure transducer valve is used to control EGR. The EGR valve is operated by ported vacuum, but the ported vacuum will normally be vented off at the EGR backpressure transducer valve. As rpm increases, exhaust pressure increases and pushes on the diaphragm in the EGR backpressure transducer valve and closes the vacuum vent.
Figure 2: EGR Backpressure Transducer Value
Item Number Description 1 — Throttle Valve 2 — Vacuum Port 3 9D475 EGR Valve 4 9F452 EGR Backpressure Transducer Valve 5 — EVAP Canister 6 — EGR/EVAP Control Solenoid 7 — Vent
EGR/EVAP Control Solenoid The exhaust gas recirculation/evaporative emission (EGR/EVAP) control solenoid (Figure 3) is controlled by the powertrain control module (PCM). The EGR/EVAP control solenoid controls vacuum to both the exhaust gas recirculation (EGR) valve and to the evaporative (EVAP) emission canister. When the EGR/EVAP control solenoid is off (12 V signal from the PCM) vacuum is supplied to both the EGR valve and to the EVAP canister. When the EGR/EVAP control solenoid is on (ground supplied by PCM) vacuum is vented to the atmosphere keeping the EGR valve closed and no vacuum to the EVAP canister. The PCM will command the EGR/EVAP control solenoid on at:

• Engine starting condition
• Low engine coolant temperature condition
• Excessively high engine coolant temperature condition
• Engine idling condition
• High engine speed condition
• Mass air flow sensor failure

Figure 3: Exhaust Gas Recirculation/Evaporative Emission (EGR/EVAP) Control Solenoid
Exhaust Gas Recirculation (EGR) Temperature Sensor
The exhaust gas recirculation (EGR) temperature sensor (Figure 4) is a thermister type sensor that monitors the temperature of the exhaust in the EGR passageway. As the EGR flow increases, the temperature increases. This process creates a change in the resistance of the sensor, which decreases as the temperature increases. The signal is sent to the powertrain control module (PCM) to indicate that the EGR system is working properly. If the EGR temperature sensor does not change resistance as the PCM expects on two consecutive drives, the malfunction indicator lamp (MIL) will be illuminated and a diagnostic trouble code (DTC) will be stored.
Figure 4: EGR Temperature Sensor Exhaust Gas Recirculation (EGR) Valve
The exhaust gas recirculation (EGR) valve (Figure 5) recirculates portions of the exhaust gas back into the intake manifold to reduce the amount of the NOx released during combustion and to reduce combustion temperature. The amount of exhaust gases that are released into the engine is proportional to the load on the engine.
Figure 5: EGR Valve