ECD SYSTEM, Diagnostic DTC:P0401, P0402, P0403, P0487

DTC Code	DTC Name
P0401	EGR Controller, MAF Too Low Compared to the Target
P0402	EGR Controller, MAF Too High Compared to the Target
P0403	MAF not within Normal Value Range
P0487	EGR System Check above Upper Limit, below Lower Limit

DESCRIPTION

The ECM adjusts the opening angle of the EGR valve and throttle valve (for EGR) to control the EGR (Exhaust Gas Recirculation) amount to reduce emissions.
When the EGR valve is closed, there is no EGR flow. (fig. 1)
When the EGR valve is opened, exhaust gas flows to the intake manifold. (fig. 2)
When the throttle valve (for EGR) opening angle becomes smaller, the pressure in the intake manifold drops. This improves the flow of exhaust gas to the intake manifold. (fig. 3)
The EGR valve is normally closed by a return spring. However, a control signal forces the valve to close when the opening becomes lower than 10%.
During deceleration, the air flow is checked (1 time per driving cycle). This check is performed by comparing the calculated theoretical amount of air flow into the cylinder (Target MAF) with the amount of air measured by the mass air flow meter (MAF).

DTC No.	DTC Detection Condition	Trouble Area	Possible to Detect
DTC No.	DTC Detection Condition	Trouble Area	Ignition Switch	Engine Run
P0401	The intake air amount remains less than the target value for 2.5 sec. or more. (1 trip detection logic)	EGR valve Throttle valve (for EGR) Mass air flow meter ECM	-	-
P0402	The intake air amount exceeds the target value for 2.5 sec. or more. (1 trip detection logic)	EGR valve Throttle valve (for EGR) Mass air flow meter ECM	-	-
P0403	Either the following condition (a) or (b) is met for 3 sec. or more: (a) MAF (Intake air volume) is above the upper limit. (b) MAF is below the lower limit. (1 trip detection logic)	EGR valve Throttle valve (for EGR) Mass air flow meter ECM	-	-
P0487	Difference between MAF (Intake air volume) of 1st and 2nd section of open loop EGR system check below or above limit. (1 trip detection logic)	EGR valve Throttle valve (for EGR) Mass air flow meter ECM	-	-

FAIL-SAFE

DTC No.	Fail-safe Operation	Fail-safe Deactivation Condition
P0401	Stops the EGR.	Next engine start.
P0402	Stops the EGR.	Next engine start.
P0403	-	-
P0487	Stops the EGR.	Next engine start.

WIRING DIAGRAM

INSPECTION PROCEDURE

Tech Tips

When DTC P0401, P0402, P0403 or P0487 is detected, check the MAF by selecting the following menu items on the intelligent tester: Powertrain / Engine and ECT / Data List / MAF.

Reference:

Idling (after warmed up): Approximately 140 mg/st
2,000 rpm: Approximately 230 mg/st

When DTC P0401, P0402, P0403 or P0487 is detected, check the EGR valve duty by selecting the following menu items on the intelligent tester: Powertrain / Engine and ECT / Data List / EGR Valve Duty.
If the ECM is replaced, variant coding (variant coding indicates the presence of vehicle accessory items, A/C, etc.) should always be performed Click here.
Before removing the ECM and the peripheral parts, wait at least 3 minute after turning the ignition switch off (If the cooling fan is operating, remove the ECM and the peripheral parts after the fan stops.).

PROCEDURE

CHECK DTC OUTPUT (OTHER THAN P0401, P0402, P0403 AND/OR P0487)

Connect the intelligent tester to the DLC3.
Turn the ignition switch to the ON position and turn the intelligent tester on.
Select the following menu items: Powertrain / Engine and ECT / DTC.

Read the DTCs.

Result

Display (DTC Output)	Proceed To
P0401, P0402, P0403 and/or P0487	A
P0401, P0402, P0403 and/or P0487 and other DTCs	B

Tech Tips

If any other codes besides P0401, P0402, P0403 and P0487 are output, perform troubleshooting for those DTCs first.

GO TO DTC CHART

PERFORM ACTIVE TEST BY INTELLIGENT TESTER (OPERATE EGR VALVE)
1. Connect the intelligent tester to the DLC3.
2. Turn the ignition switch to the ON position and turn the intelligent tester on.
3. Clear the DTC Click here.
4. Select the following menu items: Powertrain / Engine and ECT / Active Test / EGR Valve.
5. Check the operation of the EGR valve while operating it using the intelligent tester.
  
  OK
  
  Operating sound can be heard from the EGR valve.
  
  Tech Tips
  
  The valve operation can be visually checked when performing the active test with the EGR valve removed.
NG
INSPECT EGR VALVE Click here

OK
PERFORM ACTIVE TEST BY INTELLIGENT TESTER (THROTTLE VALVE (FOR EGR))
1. Connect the intelligent tester to the DLC3.
2. Turn the ignition switch to the ON position and turn the intelligent tester on.
3. Clear the DTC Click here.
4. Select the following menu items: Powertrain / Engine and ECT / Active Test / EGR Throttle.
  
  OK
  
  Operating sound can be heard from the throttle valve (for EGR).
  
  Tech Tips
  
  Visually checked the throttle valve (for EGR) during the active test can help determine the result.
NG
INSPECT THROTTLE VALVE (FOR EGR) (VOLTAGE) Click here

OK
CHECK POWER SOURCE CIRCUIT
1. Check that the battery voltage, ECM power source voltage, and the ground condition of the ECM are normal.
  
  OK
  
  The battery voltage, ECM power source voltage, and the ground condition of the ECM are normal.
  
  Tech Tips
  
  Make sure that the battery is not discharged during the inspection.
NG
REPAIR POWER SOURCE CIRCUIT

OK
REPLACE MASS AIR FLOW METER

NEXT

OK
Operating sound can be heard from the EGR valve.

OK
Operating sound can be heard from the throttle valve (for EGR).

OK
The battery voltage, ECM power source voltage, and the ground condition of the ECM are normal.

CHECK IF DTC RECURS (P0401, P0402, P0403 AND/OR P0487)

Connect the intelligent tester to the DLC3.
Clear the DTC Click here.
Start the engine and drive the vehicle for 20 minutes.
Turn the intelligent tester on.
Select the following menu items: Powertrain / Engine and ECT / DTC.

Read the DTCs displayed on the intelligent tester.

Result

Display (DTC Output)	Proceed To
No output	A
P0401, P0402, P0403 and/or P0487	B

REPLACE ECM

END

INSPECT THROTTLE VALVE (FOR EGR) (VOLTAGE)

Disconnect the B37 throttle valve (for EGR) connector.
Turn the ignition switch to the ON position.

Measure the voltage according to the value(s) in the table below.

Standard voltage

Tester Connection	Specified Condition
Throttle valve (B37-1) - Body ground	11 to 14 V

CHECK HARNESS AND CONNECTOR (EFI MAIN RELAY - THROTTLE VALVE (FOR EGR)) Click here

INSPECT THROTTLE VALVE (FOR EGR)

Disconnect the B37 throttle valve (for EGR) connector.

Measure the resistance according to the value(s) in the table below.

Standard resistance

Tester Connection	Specified Condition
1 - 2	5 to 10 Ω

REPLACE THROTTLE VALVE (FOR EGR)

CHECK HARNESS AND CONNECTOR (THROTTLE VALVE (FOR EGR) - ECM)

Disconnect the B53 ECM connector.
Disconnect the B37 throttle valve (for EGR) connector.

Measure the resistance according to the value(s) in the table below.

Standard resistance

Check for open

Tester Connection	Specified Condition
TROT (B53-47) - Throttle valve (for EGR) (B37-2)	Below 1 Ω

Check for short

Tester Connection	Specified Condition
TROT (B53-47) or Throttle valve (for EGR) (B37-2) - Body ground	10 kΩ or higher

REPAIR OR REPLACE HARNESS OR CONNECTOR

REPLACE THROTTLE VALVE (FOR EGR)

NEXT
PERFORM ACTIVE TEST BY INTELLIGENT TESTER (THROTTLE VALVE (FOR EGR))
1. Connect the intelligent tester to the DLC3.
2. Turn the ignition switch to the ON position and turn the intelligent tester on.
3. Clear the DTC Click here.
4. Select the following menu items: Powertrain / Engine and ECT / Active Test / EGR Throttle.
  
  OK
  
  Operating sound can be heard from the throttle valve (for EGR).
  
  Tech Tips
  
  Visually checked the throttle valve (for EGR) during the active test can help determine the result.
NG
REPLACE ECM

OK

END

OK
Operating sound can be heard from the throttle valve (for EGR).

CHECK HARNESS AND CONNECTOR (EFI MAIN RELAY - THROTTLE VALVE (FOR EGR))

Disconnect the B37 throttle valve (for EGR) connector.
Remove the engine room R/B.
Remove the engine room R/B lower cover.
Disconnect the 1C engine room R/B connector.

Measure the resistance according to the value(s) in the table below.

Standard resistance

Check for open

Tester Connection	Specified Condition
Throttle valve (for EGR) (B37-1) - Engine room R/B (1C-5)	Below 1 Ω

Check for short

Tester Connection	Specified Condition
Throttle valve (for EGR) (B37-1) or Engine room R/B (1C-5) - Body ground	10 kΩ or higher

REPAIR OR REPLACE HARNESS OR CONNECTOR

INSPECT EFI MAIN RELAY (VOLTAGE)

Remove the engine room R/B.
Remove the engine room R/B lower cover.
Disconnect the 1H engine room R/B connector.

Measure the voltage according to the value(s) in the table below.

Standard voltage

Tester Connection	Specified Condition
Engine room R/B (1H-1) - Body ground	11 to 14 V

CHECK AND REPAIR HARNESS AND CONNECTOR (BATTERY - EFI MAIN RELAY)

CHECK HARNESS AND CONNECTOR (EFI MAIN RELAY - ECM)

Disconnect the B54 ECM connector.
Remove the engine room R/B.
Remove the engine room R/B lower cover.
Disconnect the 1C engine room R/B connector.

Measure the resistance according to the value(s) in the table below.

Standard resistance

Check for open

Tester Connection	Specified Condition
MREL (B54-14) - Engine room R/B (1C-8)	Below 1 Ω

Check for short

Tester Connection	Specified Condition
MREL (B54-14) or Engine room R/B (1C-8) - Body ground	10 kΩ or higher

REPAIR OR REPLACE HARNESS OR CONNECTOR

REPLACE ENGINE ROOM R/B (EFI MAIN RELAY)

NEXT

CHECK IF DTC RECURS (P0401, P0402, P0403 AND/OR P0487)

Connect the intelligent tester to the DLC3.
Clear the DTC Click here.
Start the engine and drive the vehicle for 20 minutes.
Turn the intelligent tester on.
Select the following menu items: Powertrain / Engine and ECT / DTC.

Read the DTCs displayed on the intelligent tester.

Result

Display (DTC Output)	Proceed To
No output	A
P0401, P0402, P0403 and/or P0487	B

REPLACE ECM

END

INSPECT EGR VALVE

Disconnect the B39 EGR valve connector.

Measure the resistance according to the value(s) in the table below.

Standard resistance

Tester Connection	Specified Condition
2 - 3	2 to 8 Ω

REPLACE EGR VALVE

CHECK HARNESS AND CONNECTOR (EGR VALVE - ECM)

Disconnect the B53 ECM connector.
Disconnect the B39 EGR valve connector.

Measure the resistance according to the value(s) in the table below.

Standard resistance

Check for open

Tester Connection	Specified Condition
VEGLS (B53-4) - VEGLS (B39-1)	Below 1 Ω
EGLS (B53-23) - EGLS (B39-4)	Below 1 Ω
EEGLS (B53-36) - EEGLS (B39-5)	Below 1 Ω

Check for short

Tester Connection	Specified Condition
VEGLS (B53-4) or VEGLS (B39-1) - Body ground	10 kΩ or higher
EGLS (B53-23) or EGLS (B39-4) - Body ground	10 kΩ or higher
EEGLS (B53-36) or EEGLS (B39-5) - Body ground	10 kΩ or higher

REPAIR OR REPLACE HARNESS OR CONNECTOR

REPLACE EGR VALVE

NEXT
PERFORM ACTIVE TEST BY INTELLIGENT TESTER (OPERATE EGR VALVE)
1. Connect the intelligent tester to the DLC3.
2. Turn the ignition switch to the ON position and turn the intelligent tester on.
3. Clear the DTC Click here.
4. Select the following menu items: Powertrain / Engine and ECT / Active Test / EGR Valve.
5. Check the operation of the EGR valve while operating it using the intelligent tester.
  
  OK
  
  Operating sound can be heard from the EGR valve.
  
  Tech Tips
  
  The valve operation can be visually checked when performing the active test with the EGR valve removed.
NG
REPLACE ECM

OK

END