I have a 2004 Saturn Ion 2.2L. Check engine light is on. Has two codes, PO174 Bank 2 lean, and PO401 Egr Flow problem. I looked for the EGR valve, but there is only a plate covering the spot where it should be. Not sure where to go from here. Any help would be greatly appreciated.

171 is a HEGO sensor unable to switch/ 174 is for HEGO sensor also.. 401 is insufficient EGR flow!! egr valve may be clogged or need replaced!!

cleanout egr valve and troutle body . Or replace egr with new one, clean, check vacumm lines , check for clogged check , depending on modle of car you can pippoint problem as some have a common part problem depeding with make of car. But all have to do with exaust system. Insufficient flow exaust flow. Im not an expert, all I know it is related to this, I have it myself so im googling it.

Ford EGR valve

The OBDII fault code P0401 means that the engine computer has detected that the Exhaust Gas Recirculation (EGR) system flow is insufficient. Read more how the EGR system works below. What could cause the code P0401 - clogged or restricted EGR passages
- faulty EGR valve
- EGR valve stuck closed
- problems with the DPFE sensor (Ford)
- problems with hoses to the DPFE sensor (Ford)
- problem with the EGR vacuum switching valve (Toyota)
- clogged catalytic converter
- carboned up EGR temperature sensor
- vacuum supply issues at the vacuum-operated EGR valve
- electrical problems with the EGR valve control circuit
- engine computer problems
helpful website helps you with pinpoint and sou;ution related to auto make and model shows you most common cause of code reading.
www.samarins.com

Hi, a Ford P0171 is a LEAN code for cylinder bank 1, and P0174 is a LEAN code for cylinder bank 2. These codes commonly occur on many Ford vehicles, and are set when the powertrain control module (PCM) sees the air/fuel mixture is running too lean (too much air, not enough fuel).
When the Check Engine Light comes on, either one of these codes, or both, may be found when a code reader or scan tool is plugged into the vehicle diagnostic connector. IF the vehicle is driven long enough, typically both codes will be set.
A P0171 lean code for bank 1 is the cylinder bank on the RIGHT (passenger) side of the engine on Ford vehicles with a V6 or V8 engine and rear-wheel drive.


A lean fuel condition may exist if the engine is sucking in too much air and/or the fuel system is not delivering enough fuel. If bad enough, a lean fuel condition may cause lean misfire, a rough idle, hesitation or stumble when accelerating, and/or poor engine performance.
Unmetered air can enter the engine through a vacuum leak, a dirty airflow sensor that is not reading airflow accurately, an EGR valve is not closing and is leaking exhaust into the intake manifold, an EGR valve that is allowing too much flow (because the EGR differential pressure sensor that monitors EGR flow is faulty and is under-reporting EGR flow).
If the problem is not enough fuel, the underling cause may be a weak fuel pump, restricted fuel filter, leaky fuel pressure regulator or dirty fuel injectors.

A P0174 lean code for bank 2 is the cylinder bank on the LEFT (driver) side of the engine on Ford vehicles with a transverse-mounted V6 engine and front-wheel drive. This code is not set on four cylinder engines (no bank 2).
WHAT A LEAN CODE MEANS
A lean fuel condition may exist if the engine is sucking in too much air and/or the fuel system is not delivering enough fuel. If bad enough, a lean fuel condition may cause lean misfire, a rough idle, hesitation or stumble when accelerating, and/or poor engine performance . Unmetered air can enter the engine through a vacuum leak, a dirty airflow sensor that is not reading airflow accurately, an EGR valve is not closing and is leaking exhaust into the intake manifold, an EGR valve that is allowing too much flow (because the EGR differential pressure sensor that monitors EGR flow is faulty and is under-reporting EGR flow).
If the problem is not enough fuel, the underling cause may be a weak fuel pump, restricted fuel filter, leaky fuel pressure regulator or dirty fuel injectors.

A PO174 LEAN CODE FOR BANK 2 IS THE CYLINDER BANK ON THE LEFT SIDE OF THE ENGINE
(THE CYLINDERS FACING THE FRONT OF YOUR CAR)
A LEAN FUEL CONDITION COULD EXIST IF THE ENGINE IS GETING
TO MUCH AIR AND/OR NOT GETING ENOUGH FUEL
THIS CAN CAUSE MISFIRE, ROUGH IDLE, AND HESITATION WHEN ACCELERATING
THIS COULD BE
A VACUME LEAK, A DIRTY AIRFLOW SENSOR,
A EGR VALVE NOT CLOSING LEAKING EXHAUST INTO THE INTAKE MANIFOLD
IF ITS NOT GETING ENOUGH FUEL THE FUEL PUMP COULD BE BAD, THE AIR FILTER COULD BE DIRTY
OR IT COULD BE DIRTY INJECTORS
ID TRY FUEL INJECTOR CLEANER AND A NEW AIR FILTER FIRST
THEN TRY CLEANING YOUR EGR VALVE. COPY THIS LINK TO YOUR BROWSER FOR
STEP BY STEP INSTRUCTIONS TO DO THIS.
www.ehow.com/how_4809842_clean-ford-taurus-egr-valve.html

IF THIS DONT DO IT I WOULD TAKE IT TO A MECHANIC TO HAVE THE OTHER THINGS CHECKED
HOPE THIS HELPS.

I believe this code is insufficient EGR flow. On this engine, the passages to the EGR valve often become carboned up and cause this code. Remove the EGR valve and inspect the passages to see if they need to be cleaned.

How many miles are on the car? It could be one of three things.
1. Check vaccum lines running to the valve covers. The rubber nipple that connects to the valve cover sometimes gets a hole.
2. Could be 02 sensor depending if its lean on bank 1 or bank 2.
3. Also check DPFE hose's. Located on back of motor running from EGR valve exhuast tube.

P0174 means Fuel Trim too Lean (Bank 2)

P0401 means Exhaust Gas Recirculation Flow Insufficient Detected

P0420 means Catalyst System Efficiency Below Threshold (Bank 1)

Visit http://www.troublecodes.net/OBD2/

and Visit www.repairpal.com

those codes are for lean engine condition look for vac leaks at the back of engine to the pcv valve could hear hissing noise with engine running also check egr valve to be stuck open also when was last fuel filter changed? hope this helps .

Have it checked again and see what code it is. if it is P0401 it is probably the sensor shown below, The DPFE (Diferential Pressure Sensor)sensor is usually mounted on the engine and is connected to the pipe that runs from the exhaust manifold to the EGR valve with two rubber hoses. When the sensor goes bad, the Check Engine light comes on and typically sets any or all of teh following fault codes: P0171 & P0174 (lean codes), and/or P0401 (insufficient EGR flow). Nine out of ten times, the fault is not a bad EGR valve or a vacuum leak, but a bad DPFE sensor. A replacement costs about $112 at Ford, or about $48 at an aftermarket auto parts store.I hope this helps.