expected `}' at end of input
Some guidelines for programming:

Start each statement on a new line

int scvVal = 6; 
int drvVal = 9; 
int sensorVal = A1; 
void setup() { 
Serial.begin(9600); 
pinMode(6, OUTPUT); 
pinMode(9, OUTPUT);
} void loop(){ 
sensorVal = analogRead(A1);

Serial.print("Sensor Value: "); Serial.print(sensorVal);

float voltage = (sensorVal*5.0)/1024.0; Serial.print("Volts: "); Serial.print(voltage);

float pressure_pascal = (400.0*((float)voltage-0.5))*1000000.0; 
float pressure_bar = pressure_pascal/10e5; 
Serial.print("Pressure = "); 
Serial.print(pressure_bar); 
Serial.println(" bars"); 
Serial.print("Pressure = "); { 
for(int a = 255; a&gt;=0;a--) { 
analogWrite(6,a); 
if (pressure_bar = 1600){ 
analogWrite (6, a); 
if (pressure_bar &gt; 1600){ 
analogWrite (6, a); } 
for(int a = 0; a&lt;256; a++) { 
analogWrite(6, a); { 
if(pressure_bar &lt; 1600){ 
analogWrite (6, a); } 
for(int b = 255; b&gt;=0;b--) { 
analogWrite(9, b); { 
if (pressure_bar == 1600){ 
analogWrite (9, b); 
if(pressure_bar &lt; 1600){ 
analogWrite (9, b); } 
for(int b = 0; b&lt;256; b++) { 
analogWrite(9, b); { 
if (pressure_bar &gt; 1600){ 
analogWrite (9, b);
} }


Use brackets and align them

.. so each pair of { and } is on the same column and align code with brackets to be indented 2, 3 or 4 spaces

int scvVal = 6; 
int drvVal = 9; 
int sensorVal = A1; 
void setup() 
{ 
  Serial.begin(9600); 
  pinMode(6, OUTPUT); 
  pinMode(9, OUTPUT);
} 
void loop()
{ 
  sensorVal = analogRead(A1);

  Serial.print("Sensor Value: "); 
  Serial.print(sensorVal);

  float voltage = (sensorVal*5.0)/1024.0; Serial.print("Volts: "); 
  Serial.print(voltage);

  float pressure_pascal = (400.0*((float)voltage-0.5))*1000000.0; 
  float pressure_bar = pressure_pascal/10e5; 
  Serial.print("Pressure = "); 
  Serial.print(pressure_bar); 
  Serial.println(" bars"); 
  Serial.print("Pressure = "); 
  { 
    for(int a = 255; a&gt;=0;a--) 
    { 
      analogWrite(6,a); 
      if (pressure_bar = 1600)
      { 
        analogWrite (6, a); 
        if (pressure_bar &gt; 1600)
        { 
          analogWrite (6, a);  
        }   
        for(int a = 0; a&lt;256; a++) 
        { 
          analogWrite(6, a); 
          {   
            if(pressure_bar &lt; 1600)
            {   
              analogWrite (6, a); 
            } 
            for(int b = 255; b&gt;=0;b--) 
            { 
              analogWrite(9, b); 
              {  
                if (pressure_bar == 1600)
                { 
                  analogWrite (9, b); 
                  if(pressure_bar &lt; 1600)
                  {  
                    analogWrite (9, b); 
                  } 
                  for(int b = 0; b&lt;256; b++) 
                  { 
                    analogWrite(9, b); 
                    { 
                      if (pressure_bar &gt; 1600)
                      {    
                        analogWrite (9, b);
                      }
                    }


Remove superfluous brackets

As you can see, you are having some superfluous/missing brackets. What you want is probably something like:

int scvVal = 6; 
int drvVal = 9; 
int sensorVal = A1; 
void setup() 
{ 
  Serial.begin(9600); 
  pinMode(6, OUTPUT); 
  pinMode(9, OUTPUT);
} 
void loop()
{ 
  sensorVal = analogRead(A1);

  Serial.print("Sensor Value: "); 
  Serial.print(sensorVal);

  float voltage = (sensorVal*5.0)/1024.0; Serial.print("Volts: "); 
  Serial.print(voltage);

  float pressure_pascal = (400.0*((float)voltage-0.5))*1000000.0; 
  float pressure_bar = pressure_pascal/10e5; 
  Serial.print("Pressure = "); 
  Serial.print(pressure_bar); 
  Serial.println(" bars"); 
  Serial.print("Pressure = "); 

  for(int a = 255; a&gt;=0;a--) 
  { 
    analogWrite(6,a); 
    if (pressure_bar = 1600)
    { 
      analogWrite (6, a);
    }
    if (pressure_bar &gt; 1600)
    { 
      analogWrite (6, a);  
    } 
  }
  for(int a = 0; a&lt;256; a++) 
  {
    analogWrite(6, a); 
    if(pressure_bar &lt; 1600)
    {   
      analogWrite (6, a); 
    }
  } 
  for(int b = 255; b&gt;=0;b--) 
  { 
    analogWrite(9, b); 
    if (pressure_bar == 1600)
    { 
      analogWrite (9, b); 
    }
    if(pressure_bar &lt; 1600)
    {  
      analogWrite (9, b); 
    } 
  }
  for(int b = 0; b&lt;256; b++) 
  { 
    analogWrite(9, b); 
    if (pressure_bar &gt; 1600)
    {    
      analogWrite (9, b);
    }
  }
}


Remove duplicate code

In the if statement, you perform twice the same code (both you send an analogWrite with the same value, so the code (from the for loops can be reduced to:

  for(int a = 255; a&gt;=0;a--) 
  { 
    analogWrite(6,a); 
    if (pressure_bar &gt;= 1600)
    { 
      analogWrite (6, a);
    }
  }
  for(int a = 0; a&lt;256; a++) 
  {
    analogWrite(6, a); 
    if(pressure_bar &lt;= 1600)
    {   
      analogWrite (6, a); 
    }
  } 
  for(int b = 255; b&gt;=0;b--) 
  { 
    analogWrite(9, b); 
    if (pressure_bar &lt;= 1600)
    { 
      analogWrite (9, b); 
    } 
  }
  for(int b = 0; b&lt;256; b++) 
  { 
    analogWrite(9, b); 
    if (pressure_bar &gt;= 1600)
    {    
      analogWrite (9, b);
    }
  }
}


Unclear

What is unclear why you first write an analog value, and directly afterward (in each if) you write the same value. I'm not sure what you really want here. Either you want to write to a different pin, or you want a delay (to have the value having some effect), I'm just not sure.