Oct 22, 2026 at 10:37 PM
The MAP code is a side effect of how the EGR was blocked off, not extra vacuum. Your 2004 has no stand-alone MAP sensor. It is built into the EGR system module (the ESM, the box that sat on top of the EGR valve). That module has three hoses: the fat one from the EGR tube is the exhaust side, and of the two small vacuum lines you plugged, one feeds the solenoid and the other is the manifold reference for the MAP sensor. With that line plugged the sensor is reading a dead hose instead of the manifold, so the computer sees pressure that is too high and sets the MAP high code.
The computer also uses that MAP reading for other things besides EGR, so do not just ignore it. The clean fix is a new EGR tube, which puts both codes to rest. Until then, leave the module plugged in with its small manifold vacuum line hooked back up (it can sit off the manifold) and the MAP reading goes honest again; you are left with only the EGR flow code. Whether a tuner clears the MAP code depends on the tune: some turn off the EGR and its codes but still expect a sane MAP reading, so ask the tuner before you buy whether their tune handles a 2003 and later ESM car with the EGR removed.
One more thing for the next owner reading this: with the EGR off, the car will fail any emissions inspection that reads codes or looks under the hood.
Dana
