Arduino Motor Shield It seems that I can't get the DC Motor function to work while also having servos driven off the other ports :(

#include "Arduino.h"
#include &lt;Servo.h&gt;

int pinI1=8;//define I1 interface
int pinI2=11;//define I2 interface 
int speedpinA=9;//enable motor A
int pinI3=12;//define I3 interface 
int pinI4=13;//define I4 interface 
int speedpinB=10;//enable motor 
int spead =220;//define the spead of motor

Servo SteeringServo;  // create servo object to control a servo 

void setup()
{
  // Steering servo pin setup
  SteeringServo.attach(5);  // attaches the servo on pin 9 to the servo object

  pinMode(pinI1,OUTPUT);
  pinMode(pinI2,OUTPUT);
  pinMode(speedpinA,OUTPUT);
  pinMode(pinI3,OUTPUT);
  pinMode(pinI4,OUTPUT);
  pinMode(speedpinB,OUTPUT);

  Serial.begin(9600);

}

void forward()
{
     analogWrite(speedpinA,spead);//input a simulation value to set the speed
     analogWrite(speedpinB,spead);
     digitalWrite(pinI4,HIGH);//turn DC Motor B move clockwise
     digitalWrite(pinI3,LOW);
     digitalWrite(pinI2,LOW);//turn DC Motor A move anticlockwise
     digitalWrite(pinI1,HIGH);
}
void backward()//
{
     analogWrite(speedpinA,spead);//input a simulation value to set the speed
     analogWrite(speedpinB,spead);
     digitalWrite(pinI4,LOW);//turn DC Motor B move anticlockwise
     digitalWrite(pinI3,HIGH);
     digitalWrite(pinI2,HIGH);//turn DC Motor A move clockwise
     digitalWrite(pinI1,LOW);
}
void left()//
{
     analogWrite(speedpinA,spead);//input a simulation value to set the speed
     analogWrite(speedpinB,spead);
     digitalWrite(pinI4,HIGH);//turn DC Motor B move clockwise
     digitalWrite(pinI3,LOW);
     digitalWrite(pinI2,HIGH);//turn DC Motor A move clockwise
     digitalWrite(pinI1,LOW);
}
void right()//
{
     analogWrite(speedpinA,spead);//input a simulation value to set the speed
     analogWrite(speedpinB,spead);
     digitalWrite(pinI4,LOW);//turn DC Motor B move anticlockwise
     digitalWrite(pinI3,HIGH);
     digitalWrite(pinI2,LOW);//turn DC Motor A move clockwise
     digitalWrite(pinI1,HIGH);
}
void stop()//
{
     digitalWrite(speedpinA,LOW);// Unenble the pin, to stop the motor. this should be done to avid damaging the motor. 
     digitalWrite(speedpinB,LOW);
     delay(1000);

}

void loop()
{
  left();
  delay(15000);  
  stop();
  right();
  delay(1000);
 stop();
 // delay(2000); Already commented out
  //forward();
 // delay(2000);
 // stop();
// backward();
  delay(12000); 
  stop(); 
}
Your code:

int speedpinA=9;//enable motor A
...
int speedpinB=10;//enable motor 
...
 analogWrite(speedpinA,spead);//input a simulation value to set the speed
 analogWrite(speedpinB,spead);


See https://www.arduino.cc/en/reference/servo


  On boards other than the Mega, use of the library disables analogWrite() (PWM) functionality on pins 9 and 10, whether or not there is a Servo on those pins.


(My emphasis).

So, you can't do that, exactly. Perhaps choose other pins for the analogWrite, pins that analogWrite supports, that are not 9 and 10.