I am having a similar problem with my truck, I am getting the P0402 code. I
found this information on the net. It may help you out. My light comes on
every 200 or so miles, or when my wife drives my truck. You said you cleaned
the filter on you EGR valve, is that easy to remove?

DTC P0402: EXCESSIVE EXHAUST GAS RECIRCULATION (EGR) FLOW DETECTED

CAUTION: If ECM replacement is instructed in following testing,
and ground circuit are okay. If either are suspect,
malfunction.

Circuit Description

The EGR system recirculates exhaust gas through intake system to
EGR valve opening is regulated by the EGR Vacuum Switching Valve
VSV is controlled by the Vacuum Control Valve (VCV). Amount of EGR
which is mounted on EGR valve.

The EGR valve is closed (VSV on) under the following conditions:

Engine is not warmed up.
Vehicle under deceleration.
Light engine load.
Engine speed more than 4000 RPM.
Engine idling.
Code is set when EGR cut-off, lift amount of EGR valve is .1" (2.6

EGR valve stuck open.
EGR Vacuum Switching Valve (VSV).
EGR VSV open circuit.
EGR valve position sensor open or short circuit.
EGR valve position sensor.
ECM.
Test Drive Confirmation

1.Connect scan tool. See Fig. 1. Start and warm engine to normal
minutes or more. Stop vehicle and allow to idle for about 2
2.Start engine and allow to idle. Operate vehicle at 43-56 MPH
minutes.
3.Check READINESS TESTS. If COMPL is displayed on scan tool and
displayed and MIL is not illuminated, repeat test drive

Diagnosis & Repair (Using Toyota Scan Tool)

1.Check all EGR system vacuum hoses. See appropriate
hoses as necessary. If all hoses are okay, check EGR VSV.
VSV when activated by scan tool. VSV is located under "V" bank
Go to next step.
2.With EGR system off, air from port "E" should flow from port
flow from port "F". If VSV operates as specified, go to step
3.Remove EGR VSV. Using ohmmeter, measure resistance between VSV
(20° C). Measure resistance between each terminal and body of
specified, replace VSV. If resistance is as specified, go to
4.Check VSV operation. Apply battery voltage to VSV terminals.
"F". Remove battery voltage from VSV terminals. Air should
specifications in steps 3) and 4), check for a short in EGR
diagram in L - WIRING DIAGRAMS article. Repair wiring as
5.Disconnect vacuum hose from EGR valve. Connect a vacuum pump

If engine does not run rough or stall, replace EGR valve. If
engine runs rough or stalls, check EGR valve position sensor.
See appropriate I - SYSTEM/COMPONENT TESTS article. Replace
position sensor as necessary. If position sensor is okay,
replace ECM.

Diagnosis & Repair (Using OBD-II Scan Tool)

1.Check all EGR system vacuum hoses. Replace hoses as necessary.
If vacuum hoses are okay, access ECM behind glove box. Ensure
ignition is off. On models with Calif. emissions and except
Calif. emissions with engine immobilizer system and/or
traction control, disconnect ECM E11 connector. See Fig. 2.
Connect a jumper wire between ground and terminal No. 18
(Yellow/Green wire) at ECM E11 connector. Go to next step. On
except Calif. emission models without engine immobilizer
system and/or traction control, disconnect ECM E8 connector.
See Fig. 3. Connect a jumper wire between ground and terminal
No. 12 (Yellow/Green wire) at ECM E8 connector. Go to next
step.

NOTE: For information on engine immobilizer system, see
COMPUTERIZED ENGINE CONTROLS in E -
THEORY/OPERATION article.

2.On all models, apply air pressure to EGR Vacuum Switching
Valve (VSV) port "E". VSV is located under "V" bank cover on
top of engine. With jumper wire connected, air should flow
from port "F". See Fig. 6. With jumper wire disconnected, air
should flow from port "G". If VSV operates as specified, go to
step 5). If VSV does not operate as specified, go to next
step.
3.Remove EGR VSV. Using ohmmeter, measure resistance between VSV
terminals. Resistance should be 27-33 ohms at 68° F (20° C).
Measure resistance between each terminal and body of VSV.
Resistance should be infinite. If resistance is not as
specified, replace VSV. If resistance is as specified, go to
next step.
4.Check VSV operation. Apply battery voltage to VSV terminals.
Apply air pressure to VSV port "E". Air should flow from port
"F". See Fig. 6. Remove battery voltage from VSV terminals.
Air should flow from port "G". Replace VSV as necessary. If
VSV meets all specifications in steps 3) and 4), check for
short in EGR VSV circuits between engine compartment fuse box
and ECM. See appropriate wiring diagram in L - WIRING DIAGRAMS
article. Repair wiring as necessary.
5.Disconnect vacuum hose from EGR valve. Connect a vacuum pump
to EGR valve. Start engine. Apply vacuum to EGR valve. If
engine does not run rough or stall, replace EGR valve. If
engine runs rough or stalls, check EGR valve position sensor.
See appropriate I - SYSTEM/COMPONENT TESTS article. Replace as
necessary. If EGR position sensor is okay, replace ECM.