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Secondary Air Injection
Damaged or malfunctioning secondary air injection system (mechanically stuck valve).
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Engine Mechanical
Engine oil overfilled, cam timing, cylinder compression or exhaust leaks before or near HO2S.
Ensure MAF sensor is connected. Start engine and bring to normal operating temperature. Using scan
tool, access BARO, LONGFT1, LONGFT2 and MAF V PIDs. Check the following:
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Ensure BARO PID is about the same as barometric pressure measurement for location, day and
altitude of area. See Fig. 185.
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Ensure BARO PID values in Keep Alive Memory have been updated. If vehicle is driven down
from higher altitudes for diagnosing, complete 3 or 4 heavy accelerations at more than 1/2 throttle
to allow BARO PID to update.
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Ensure BARO PID is within plus or minus 6 Hz (plus or minus 2 in. Hg) of altitude value. Refer to
illustration. See Fig. 185.
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Ensure LONGFT1, LONGFT2 PIDs for all injector banks at idle are not more than minus 12
percent.
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Ensure MAF V PID at idle in gear or neutral is not more than 30 percent (no more than 1.1 volt) of
normal MAF V listed in appropriate pin voltage/PID value chart in appropriate PIN
VOLTAGE/PID VALUE CHARTS article.
If 2 out of the 3 checks are not within specification, go to next step. If 2 out of the 3 checks are within
specification and DTCs P0171, P0172, P0174, P0175, P1130, P1131, P1132, P1150, P1151, P1152,
P2195, P2196, P2197 or P2198 are present, go to TEST H, step 42) (gasoline vehicles), or TEST HA,
step 42) (natural gas vehicles). If 2 out of the 3 checks are within specification and no DTCs are present
but driveability concern still exists, diagnose by symptom. See SYMPTOMS in TROUBLE SHOOTING
- NO CODES - CNG, FLEX-FUEL & GASOLINE article.
26) Check To Isolate MAF Sensor From Lean Driveability Occurrence
Disconnect MAF sensor connector. Start engine and drive vehicle. If lean driveability symptom (lack of
power, spark knock, detonation, buck, jerk or hesitation on acceleration) is gone, replace MAF sensor. If
lean driveability symptom still exists and DTCs P0171, P0172, P0174, P0175, P1130, P1131, P1132,
P1150, P1151 or P1152 are present, go to TEST H, step 42) (gasoline vehicles), or TEST HA, step 42)
(natural gas vehicles). If lean driveability symptom did not disappear and no DTCs are present, diagnose
by symptom. See SYMPTOMS under TROUBLE SHOOTING - NO CODES - CNG, FLEX-FUEL &
GASOLINE article.
NOTE:
OBD-II requirements call for a fuel system DTC to be set on some vehicles
although a driveability concern may not be noticeable, with or without the
MAF sensor disconnected. If this should occur and BARO, LONGFT1,
LONGFT2 and MAF V PID indicate a MAF sensor concern, replace MAF
sensor.
2003 Ford Pickup F150
2003 ENGINE PERFORMANCE Self-Diagnostics - CNG, Flex-Fuel & Gasoline