The engine light comes on and a mechicanic plug in a computer thing and it said there is a problem with my EGR flow. what is the problem and how do I fix it.

Here is a list of possible causes. Some things you have already done.

EGR solenoid valve harness is open or shorted
- EGR solenoid valve circuit poor electrical connection
- EGR volume control valve stuck closed
- Faulty EGR Pressure sensor
- Faulty EGR temperature sensor and circuit
- Faulty EGR Valve
- EGR passage clogged
- Exhaust gas leaks
Read more: http://engine-codes.com/p0401_ford.html#ixzz28fATCih2

Are you sure you have EGR flow?? Hold the EGR valve open the engine should run poorly, if not you have no flow.

This is not a cut and dry fault code. This means that more than one thing wrong can set the code in the computers memory. Here is the low down on the P0402 fault code. This is from the OBD2 fault code diagnostic book.

P0402 - Exhaust Gas Recirculation Flow Excessive Detected
Symptoms - Engine Light ON (or Service Engine Soon Warning Light)
- Possible engine hesitation
Possible causes - EGR solenoid valve harness is open or shorted
- EGR solenoid valve circuit poor electrical connection
- EGR volume control valve stuck closed
- Dead (Weak) battery
- Faulty EGR temperature sensor and circuit
- Faulty EGR Valve
- EGR passage clogged
- Exhaust gas leaks

yes a hose not connected will cause a malfuncition light but the egr can also get plugged

take battery cable off to let computer reset

Could be clogged egr passages in the intake. Also could be just do to a reflash needed of the computer. GM has come up with new software for the computer to fix this problem.

how I change the EGR valve assist switch for toyota camry 2000

Sometimes you need to reset the computer. Try disconnecting the battery.

have the EGR valve tested because this will cause the engine light to come on and also check all vacuum lines

Insufficient EGR Flow Detected

Possible Causes:
DPFE sensor signal circuit is shorted to ground
DPFE sensor VREF circuit is open between sensor and PCM
DPFE sensor downstream hose off or plugged
DPFE sensor hoses both off, loose or damaged
DPFE sensor hoses connected wrong (reversed)
EGR orifice tube is damaged or restricted
PCM has failed
And what sets the code is…….Engine started, engine running in closed loop under steady cruise conditions, and the PCM detected the DPFE sensor input indicated insufficient EGR gas flow. Run the KOER Self-Test, and if DTC P1408 is present, the fault is currently present. This code sets in 2 Trip(s). The light will stay on until the cause is repaired. A bad EGR valve is only on possible cause.

Hope this helps,

Dave