Here's the definition: Intake Air Control circuit malfunction
And since the IAC is mentioned, see "Related Questions" below to get started
Trouble code P1504 means: Idle air control (IAC) circuit malfunction
Trouble code P1504 means: Idle air control (IAC) circuit malfunction Trouble code P1507 means: Idle air control (IAC) underspeed error
erg valve stuck in closed position
The collection of "Related Questions" below provide excellent coverage to the various aspects of the EGR/secondary air system problems on Taurus/Sables.Start with the question regarding the 401 check engine light "diagnostic trouble code" (DTC). Lots of great information to jump-start the trouble-shooting, diagnostics and fixing efforts.
Trouble code P1320 means: Distributor Signal Interrupt
Trouble code P0401 means: Insufficient EGR Flow Detected Replace the EGR valve
Trouble code P0731 means: Incorrect gear ratio, first gear
running lean. too many possibilities to narrow down
Trouble code P0340 means:Camshaft position sensor circuit malfunction
Trouble code P0720 means: Output Shaft Speed Sensor Circuit
Trouble code P0136 means: O2 Circuit (Bank 1, Sensor 2)
Trouble code P1870 means: Transaxle Component Slipping (4T60-E)