2000 Isuzu Trooper LS 6 Cyl 3.50L
po401 egr code map sensor no change volts
170,000 work good all around except po401 code you erase and back after 5 miles, clean EGR valve check map sensor is ok but don't change volt always the same 5.06 volt I test it with a hand vacuum and from 5 psi to 20 is no change I don't know where to located the problem I do have an alldatadiy book I change one oxygen sensor was bad now all 4 working ok.
The EGR passages are clogged up solid. Unbolt the throttle body to be able access the EGR tube, use a coat hanger to clean out the tube. To prove that the passages are clogged would require you to attach a scan tool that you do not have and command the EGR valve on and see the engine stall out or run very rough and if after commanding the EGR valve to open while idling the engine runs with little or no change, this confirms that the passages are clogged. So that being said, just trust me, the passages are your cause with a near 100% probability.