valve(s). Check hose for cracks, blockage, restrictions, kinks, poor connections, obstructions or water or
ice (in colder climates). Replace or repair hose as necessary. If hose is okay, go to next step.
33) Check AIR By-Pass Solenoid Electrical Operation
Ensure scan tool is connected to DLC. Disconnect air by-pass solenoid connector. Turn ignition switch to
ON position. Using scan tool, access OUTPUT TEST MODE. Connect DVOM between both AIR by-
pass solenoid harness connector terminals. See Fig. 249. Observe DVOM voltage reading while cycling
outputs first ON, and then OFF. If voltage reading cycles more than 0.5 volt, remain in OUTPUT TEST
MODE and go to next step. If voltage reading does not cycle more than 0.5 volt, turn ignition switch to
OFF position and go to step 35).
34) Check AIR By-Pass Solenoid For Mechanical Operation
Ensure scan tool is in OUTPUT TEST MODE. Reconnect AIR by-pass solenoid harness connector.
Disconnect source vacuum hose from AIR by-pass solenoid. Connect hand vacuum pump to vacuum
source side of AIR by-pass solenoid. Apply 16 in. Hg (54 kPa) to AIR by-pass solenoid. Observe DVOM
while cycling outputs ON and OFF. If vacuum does not release as outputs are cycled ON and OFF,
replace AIR by-pass solenoid. If vacuum releases as outputs are cycled ON and OFF, repair vacuum hose
between AIR by-pass solenoid and intake manifold vacuum tree. If hose is okay, go to TEST Z, step 2).
35) Check Air By-Pass Solenoid Resistance
Turn ignition switch to OFF position. Disconnect AIR by-pass solenoid harness connector. Using a
DVOM, measure resistance between both AIR by-pass solenoid terminals. If resistance is 50-100 ohms,
go to next step. If resistance is not 50-100 ohms, replace AIR by-pass solenoid.
36) Check VPWR Circuit For Open In Harness
Turn ignition switch to ON position. Using a DVOM, measure voltage between negative battery terminal
and VPWR circuit at AIR by-pass solenoid harness connector. See Fig. 249. If voltage is more than 10.5
volts, go to next step. If voltage is 10.5 volts or less, repair open in VPWR circuit. On LS V6, ensure
dedicated B+ circuit fuse is okay.
37) Check EAIR Circuit For Open In Harness
Turn ignition switch to OFF position. Disconnect SSR and PCM connector(s). Using a DVOM, measure
resistance of EAIR circuit between PCM harness connector, AIR by-pass solenoid harness connector and
SSR harness connector. See PCM CONNECTOR IDENTIFICATION and Fig. 249. If any resistance
measurement is 5 ohms or more, repair open in EAIR circuit. If both resistance measurements are less
than 5 ohms, go to next step.
38) Check EAIR Circuit For Short To Ground In Harness
Turn ignition switch to OFF position. Using a DVOM, measure resistance between EAIR and PWR GND
circuits at PCM harness connector. See PCM PWR GND, SIG RTN & VREF TERMINAL
IDENTIFICATION table. See PCM CONNECTOR IDENTIFICATION and Fig. 249. If resistance
2003 Ford Pickup F150
2003 ENGINE PERFORMANCE Self-Diagnostics - CNG, Flex-Fuel & Gasoline