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DIAGNOSTIC TROUBLE CODE (DTC) - P0400 ELECTRIC EXHAUST GAS RECIRCULATION OUT OF LIMIT

 

Knowing The Circuit

  • By any chance if high combustion temperatures are created by oxides of nitrogen then An Electric Exhaust Gas Re-circulation (EEGR) system which is the chief feature of this system will be boosted to counter this.
  • This is done by supplying small amounts of exhaust gases back into the combustion chamber.
  • Combustion temperatures are minimized as soon as the air/ fuel mixture dilutes the exhaust gases.
  • The EEGR valve has been specially designed to generate exhaust gases to the engine without using intake manifold vacuum.
  •  This valve regulates exhaust flow entering the intake manifold from the exhaust manifold through an orifice with an ECM controlled pintle.
  • The pintle position is monitored by the ECM using inputs from the Throttle Position (TP) and the Manifold Absolute Pressure (MAP) sensor.
  • This task over, the ECM then directs the EEGR valve to operate as necessary by controlling an ignition signal through the ECM.
  • The ECM further monitors the results of its command through a feedback signal.
  • The desired EEGR position can be checked with the help of a scan tool.
  • A voltage signal representing the EEGR valve pintle position is sent to the ECM by a 5 volt reference and a ground to the EEGR valve.
  • The scan tool can also be used here to note the feedback signal which is the actual position of the EEGR pintle.
  • The correct EEGR position should always be close to the commanded or Desired EEGR position.
  • This Diagnostic Trouble Code (DTC) is capable of identifying an open or short circuit.

 

       When does DTC set?

DTC sets under the following circumstances:

 

WHEN

ü        Engine Coolant Temperature (ECT) > than 80°C (176°F).

ü       Intake Air Temperature (IAT) > than 15°C (59°F).

ü       Manifold Absolute Pressure > than 75kPA.

ü       The EEGR > than 3%.

ü       Mass Air Flow is <=92 and >= 157mg/tdc.

ü       Engine Speed <=2,500and >=2,900rpm.

ü       DTCs P0107, P0108, P0112, P0113, P0117, P0118, P0122, P0123, P0131, P0300, P0335, P0336, P0341, P0342, P1671, P1672, P1673 are NOT SET.

What happens when DTC sets?

When will DTC clear?

1) The Malfunction Indicator Lamp (MIL) will start glowing

1) The MIL will turn off after four successive ignition cycles in which the diagnostic runs faultlessly.

 

2) The ECM will record operating conditions at the time when the diagnostic fails the information of which will be stored in the Freeze Frame and Failure Records will buffer

2) A history DTC will clear automatically after 40 consecutive warm-up cycles without a fault.

 

3) A history DTC will be stored.

 

3) Scan tools clear every DTC

SUMMARY OF STEPS TO BE UNDERTAKEN.

DTC P0400 - Electric Exhaust Gas Recirculation Out of Limit

  

Step

Task

Value(s)

R   E   S

U   L  T

1

Undertake the EOBD System Check.

 

Test Over?

 

-

 IF  YES       THEN

Follow Step 2

IF  NO      THEN

Go to "On-Board Diagnostic System Check"

2
  1. Turn the ignition switch to ON keeping the engine OFF.
  2. Insert the scan tool.
  3. Direct the electric exhaust gas recirculation (EEGR) valve to the values stated.

Do you see the Actual EEGR Position following the desired EEGR position?

25%, 50%, 75%, 100%

IF  YES       THEN

Follow Step19

IF  NO     THEN

Follow Step3

3
  1. Turn ON the ignition switch.
  2. Dissociate the EEGR valve electrical connector.
  3. Examine the ground circuit to the EEGR valve leaving the test light connected to B+.

Do you see the test light glowing?

-

IF  YES       THEN

Follow Step 4

IF  NO      THEN

Follow Step 5

3
  1. Connect the test light to ground.
  2. Examine the EEGR control circuit at terminal 1 connected to the EEGR valve.
  3. Direct the EEGR valve to the specified values taking the scan tool.

 Do you see the test light a) changing brighter b) flashing or c) maintaining a steady glow?

25%, 50%, 75%, 100%

IF  YES       THEN

Follow Step 6

IF  NO       THEN

Follow Step 7

5

Correct the open or poor connection in the EEGR ground circuit.

 

Task complete?

-

IF  YES       THEN

Follow Step 19

-

6

Keeping a test light still connected to ground, check the signal circuit at terminal 1.

 

Do you observe the test light glowing?

-

IF  YES       THEN

Follow Step 8

IF  NO     THEN

Follow Step 9

7

With a test light still connected to ground, again Examine the signal circuit without disturbing the EEGR valve with the scan tool. Make sure that the test light remains attached to the ground without being disconnected as you carry this task.

 

Do you see the test light glowing?

-

IF  YES       THEN

Follow Step 10

IF  NO     THEN

Follow Step 11

8

Probe the signal circuit for a short to voltage and repair as necessary.

 

Do you think that a repair is mandatory?

-

Follow Step

19

Follow Step 12

9

Survey the 5V reference circuit at terminal 3 keeping a digital voltmeter (DVM) connected to the ground.

 

Do you see that the measured voltage is anywhere near the value stated?

5V

IF  YES       THEN

Follow Step 13

IF  NO      THEN

Follow Step 14

10

Look at the control circuit and see if there is a short to battery voltage and repair if necessary.

 

Do you think it necessitates a repair?

-

IF  YES       THEN

Follow Step19

IF  NO     THEN

Follow Step12

11

Connect the test light to B+ and again survey the control circuit at terminal 4.

 

Do you see the test light glowing?

-

IF  YES       THEN

Follow Step 15

IF  NO     THEN

Follow Step 16

12

Substitute the engine control module (ECM).

 

Substitution Done?

-

IF  YES       THEN

Follow Step 19

-

13

Inspect the EEGR ground circuit for a weak connection or proper terminal tension at the ECM and mend if necessary.

 

Task Done?

-

IF  YES       THEN

Follow Step19

IF  NO       THEN

Follow Step17

14

Now inspect the 5V reference circuit to look for a shortage to battery voltage and mend if necessary.

 

Task Over?

-

IF  YES       THEN

Follow Step 19

IF  NO      THEN

Follow Step 12

15

See whether there exists any shortage to ground at the control circuit and repair if necessary.

 

Work Done?

-

IF  YES       THEN

Follow Step 19

IF  NO   THEN

Follow Step 12

16

Now check the control circuit for an open or weak connection at the EEGR valve electrical connector and see if any repair necessitates.

 

Work Done?

-

IF  YES       THEN

Follow Step 19

IF  NO       THEN

Follow Step 18

17

Change the EEGR valve.

 

Is the change over?

-

IF  YES       THEN

Follow Step 19

-

18

Survey the ECM electrical connector for a weak connection and mend it if needed.

 

Task Over?

-

IF  YES       THEN

Follow Step 19

IF  NO       THEN

Follow Step 12

19

      1) Unset the DTCs, taking a scan tool.

2) Start the engine and idle at normal operating temperature.

3) Run the vehicle within the parameters needed for setting this DTC as mentioned in the supporting text.

Does the scan tool indicate that this diagnostic has been run and passed?

 

IF  YES       THEN

Follow Step 20

IF  NO     THEN

Follow Step 2

20

Check if any additional DTCs are set.

 

Do you see any undiagnosed DTC still being displayed?

 

IF  YES       THEN

Go to Applicable DTC table

IF  NO      THEN

The System of your car is fine.



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