P9494 is the EGR valve circuit range. This is usually caused by the sensor in the EGR valve failing so that it doesn't report the position of the pintle inside the valve to the PCM correctly. To test it requires a scan tool to read the sensor while commanding the EGR valve to open and close. Without the scan tool to test the EGR the next option is changing the EGR valve, because the normal cause is that the pintle itself corrodes so that it binds and cannot move easily so the sensor doesn't move either. The hard part of changing it is usually that the bolts securing it corrode as well and cause problems.
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Thursday, September 26th, 2019 AT 1:31 PM