EGR CONTROL OPERATION [L3 R.H.D.]

BUE014000000N30

Stepping Motor Operation Principles

• The PCM opens/closes the EGR valve by controlling the amount of stepping motor rotation (step number).
• The stepping motor operates by the combination of coils No.1-4 according to the stepping motor step number.

Energization condition for each coil

ON: Energization OFF: Non-energization

When current step number divided by four

Evenly divisible

One leftover

Two leftover

Three leftover

Coil No.1 (PCM terminal 56)
ON
ON
OFF
OFF
Coil No.2 (PCM terminal 30)
OFF
OFF
ON
ON
Coil No.3 (PCM terminal 57)
OFF
ON
ON
OFF
Coil No.4 (PCM terminal 31)
ON
OFF
OFF
ON

Example of energization condition for each coil and step number

ON: Energization OFF: Non-energization

Step number

0

1

2

3

4

5

6

7

8

9

10

30

52

Coil No.1 (PCM terminal 56)
ON
ON
OFF
OFF
ON
ON
OFF
OFF
ON
ON
OFF
OFF
ON
Coil No.2 (PCM terminal 30)
OFF
OFF
ON
ON
OFF
OFF
ON
ON
OFF
OFF
ON
ON
OFF
Coil No.3 (PCM terminal 57)
OFF
ON
ON
OFF
OFF
ON
ON
OFF
OFF
ON
ON
ON
OFF
Coil No.4 (PCM terminal 31)
ON
OFF
OFF
ON
ON
OFF
OFF
ON
ON
OFF
OFF
OFF
ON
• The energization condition of stepping motor coils No.1-4 can be verified by verifying the step number from "SEGRP" on the PID/data monitor function of the WDS or equivalent.

Control outline

• The PCM constantly calculates the optimum target EGR valve position according to the engine operation conditions and controls the EGR stepping motor step number so that the current EGR valve position is close to the target.
• If the current EGR valve position is smaller than the target EGR position (deviation is a positive number), the PCM increases the stepping motor step number and opens the EGR valve. If larger (deviation is a negative number), the PCM decreases the stepping motor step number and closes the EGR valve. Step numbers are increased or decreased by one step at a time.

Target EGR valve position

• The PCM determines the value to increase or decrease the EGR valve opening angle according to the engine operation conditions. The PCM determines the target EGR valve position through each correction based on the basic EGR valve position that is set according to the engine speed and load.

Target EGR valve position determination method table

Contents

Method for calculating or determining the EGR valve position and correction

Basic EGR valve position
Within steps 0-52 in the stepping motor determined as follows:
• When the engine speed is 1,000-4,000 rpm and the charging efficiency*1 is within 11.7-75%, the engine speed and charging efficiency are determined to be at basic position
• When the EGR control inhibition conditions are met, step 0
Correction *2
ECT correction
Purpose: Improved driveability
Engine coolant temperature is 50-55°C {122-131 °F}
• The step number is restricted between 0-50% of the basic EGR valve position according to the engine coolant temperature. (Low engine coolant temperature→low step number)
Engine coolant temperature is 55-65°C {131-149 °F}
• The step number is restricted between 50-100% of the basic EGR valve position according to the engine coolant temperature. (Low engine coolant temperature→low step number)
IAT correction
Purpose: Improved driveability
Intake air temperature is 50°C {122°F} or less
• Step number is restricted to 100% of the basic EGR valve position (basic EGR valve position = step number)
Intake air temperature is 50°C {122°F} or less
• Step number is restricted between 40-100% of basic EGR valve position (low intake air temperature→large step number)
Acceleration/deceleration correction
Purpose: Improved driveability
During acceleration/deceleration, when the throttle valve opening angle fluctuation rate is the set value or more
• During acceleration→step number is restricted to 20% of basic EGR value position.
• During deceleration→step number is restricted to 0% of basic EGR valve position

*1 :
Charging efficiency is the ratio of the actual amount of intake air to the maximum air charging amount (mass volume) of the cylinder. This value increases proportionately to the increase in engine load.
*2 :
The correction is to restrict the basic EGR valve position value. Except for the above conditions and inhibition conditions, the correction value is 100% , and the target EGR valve position equals the basic EGR valve position value.

Inhibition condition

• To improve driveability and ensure exhaust emission performance, the EGR valve closes when any of the following conditions are met. ( ) indicate input/output parts.
-• When throttle valve is fully closed (throttle position sensor)
-• Vehicle speed is 3.8 km/h {2.4 mph} or less (speed sensor)
-• When the fuel injection control is in the high load volume increase zone
-• Engine coolant temperature is 0°C {32°F} or less (ECT sensor).
-• Engine speed is less than 1,000 rpm or more than 4,000 rpm (CKP sensor)
-• Charging efficiency is above set value (CKP sensor, MAF sensor)
- During traction control