BARO PID readings with specifications in BARO SENSOR SPECIFICATIONS table. If BARO PID
value is within specification, concern is not present at this time, go to TEST Z, step 1). If BARO PID
value is not within specification, go to next step. If BARO PID value is not within specification and DTC
P0108 was retrieved, go to step 7).
2) Check VREF Voltage To BARO Sensor
Disconnect BARO sensor connector. Using a DVOM, measure voltage between VREF and SIG RTN
circuits at BARO sensor harness connector. See Fig. 202. If voltage is 4-6 volts, go to step 5). If voltage
is not 4-6 volts, go to next step.
3) Check VREF Circuit For Open
Using a DVOM, measure resistance of VREF circuit between PCM harness connector and BARO sensor
harness connector. See Fig. 202. If resistance is less than 5 ohms, go to next step. If resistance is 5 ohms
or more, repair open VREF circuit.
4) Check For VREF Circuit Short To Ground
Using a DVOM, measure resistance between VREF circuit, and SIG RTN circuit at PCM harness
connector, and negative battery terminal. See Fig. 202. If either resistance measurement is 10 k/ohms or
less, repair short in affected circuit. If both resistance measurements are more than 10 k/ohms, go to next
step.
5) Check BARO SIG & SIG RTN Circuit For Open
Using a DVOM, measure resistance of BARO SIG and SIG RTN circuits between PCM harness
connector and BARO sensor harness connector. See Fig. 202. If either resistance measurement is 5 ohms
or more, repair open circuit. If both resistance measurements are less than 5 ohms, go to next step.
6) Check BARO Circuit For Short To Ground
Using a DVOM, measure resistance between BARO circuit, and SIG RTN circuit at PCM harness
connector, and negative battery terminal. See Fig. 202. If both resistance measurements are more than 10
k/ohms, replace BARO sensor. If concern is still present, replace PCM. If either resistance measurement
is 10 k/ohms or less, repair short in affected circuit.
7) DTC P0108: Induce Opposite Code
Disconnect BARO sensor connector. Turn ignition switch to ON position. Check for DTCs. If DTC
P0107 is present, replace BARO sensor. If DTC P0107 is not present, go to next step.
8) Check BARO SIG For Short To Power
Turn ignition switch to OFF position. Using a DVOM, measure resistance between BARO SIG and
VPWR circuits at PCM harness connector. See Fig. 202. If resistance measurement is more than 10
k/ohms, replace PCM. If resistance measurement is 10 k/ohms or less, repair short to VPWR in BARO
2003 Ford Pickup F150
2003 ENGINE PERFORMANCE Self-Diagnostics - CNG, Flex-Fuel & Gasoline