Diagnostic Aids

Check all throttle body and EGR valve vacuum hoses. Check MAP sensor vacuum hose for leaks or restrictions. Ensure ignition timing is set to specification. Check for restricted exhaust system. Check for sticking or clogged EGR valve. DTC P0400 can be set when expected change in MAP sensor input is not within specified value. Any condition that can affect MAP sensor readings should be inspected.

An intermittent malfunction may be caused by a poor connection, rubbed-through wire insulation, or a wire broken inside insulation. Inspect harness connectors for backed out terminals, improper mating, broken locks, improperly formed or damaged terminals, or poor terminal-to-wire connections before component replacement.