2001 Honda Accord P1498

Its probably cracked open-see info below

A lift sensor on top of the EGR valve works just like a TPS sensor. There are three wires: a signal wire (yellow or white/blue) that goes back to the ECM, a 5-volt reference wire and a ground wire. With the EGR valve closed, the voltage should be about 1.2 volts. Normally anything more than 1.4 volts will set the light because the ECM thinks the EGR valve is open when it should not be. The voltage will increase as the valve opens. The ECM watches the voltage and then compares it to the predetermined values set in the programming of the ECM. The EGR is lifted by engine vacuum and the ECM has a solenoid it grounds when it commands EGR operation. The ECM will ground this solenoid when it sees the correct engine temperature, correct MAP sensor voltage, and throttle position sensor voltage. With the solenoid, the constant vacuum control (CVC) valve controls a constant vacuum for EGR operation. This valve takes the manifold vacuum signal and puts it to a constant 8 to 10 inches. Without a constant vacuum signal, EGR operation would be erratic. The EGR solenoid and the CVC valve location varies by model, but are often found in the black emission boxes under the hood on the fire wall. To locate, use a component locator or just follow the vacuum line.

Good Luck

You need to open it up and investigate thoroughly-just don't throw parts at it-could be the valve/wiring/computer

Did you open it up? If its carboned-up the pintle/stem won't move.