Ford F150 Pickup. Manual — part 1485

VR type sensors are susceptible to electrical interference (noise). Harness shielding, where present,
should be reinstalled properly when removed for testing. Using DVOM, measure resistance of CMP and
SIG RTN circuits between PCM harness connector and CMP sensor harness connector. If resistance
measurements are less than 5.0 ohms for each wire, go to next step. If resistance measurements are 5.0
ohms or more for either wire, repair open circuit.

10) Check For Short In Harness Between PCM & CMP Sensor

Using DVOM, measure resistance between CMP and SIG RTN circuit (at either PCM or CMP sensor
harness connector). Measure resistance between CMP circuit and battery (-) terminal. Measure resistance
between SIG RTN circuit and battery (-) terminal. If resistance(s) is(are) less than 10 k/ohms on any
measurement, repair short circuit. If resistances are all more than 10 k/ohms, go to next step.

11) Check For Shorts In PCM

Reconnect PCM harness connector(s). Using DVOM, measure resistance between CMP and SIG RTN
circuits at CMP sensor harness connector. See Fig. 209-Fig. 210 . If all resistance measurements are more
than 500 ohms, go to next step. If any resistance measurement is 500 ohms or less, replace PCM.

12) Check CMP Sensor Output

Turn ignition switch to OFF position. Reconnect CMP sensor harness connector. Set DVOM on AC scale
to monitor less than 5 volts. Start engine. Using a DVOM, measure voltage between CMP and SIG RTN
circuits at CMP sensor harness connector running engine at approximately 2500 RPM. If AC voltage is
more than .25 volt, replace PCM. If AC voltage is not more than .25 volt, replace CMP sensor.

13) Check VPWR Voltage To CMP Sensor

Disconnect CMP sensor connector. Turn ignition switch to ON position, with engine OFF. Using DVOM,
measure VPWR circuit voltage between CMP sensor harness connector and battery (-) terminal. If
voltage is greater than 10.5 volts, go to next step. If voltage is 10.5 volts or less, repair open circuit.

14) Check PWR GND Voltage To CMP Sensor

Turn ignition switch to OFF position. Using DVOM, measure PWR GND circuit voltage between CMP
sensor harness connector and battery (+) terminal. If voltage is greater than 10.5 volts, go to next step. If
voltage is 10.5 volts or less, repair open circuit.

15) Check CMP Circuit For Short To Power In Harness

Disconnect PCM connector. Turn ignition switch to ON position, with engine OFF. Using DVOM,
measure voltage between CMP circuit (at PCM or CMP harness connector) and ground. If voltage is less
than 1.0 volt, go to next step. If voltage is 1.0 volt or more, repair short circuit.

16) Check For Open Circuits Between PCM And CMP Sensor

Turn ignition switch to OFF position. Disconnect PCM and CMP sensor connectors. Using DVOM,

2003 Ford Pickup F150

2003 ENGINE PERFORMANCE Self-Diagnostics - CNG, Flex-Fuel & Gasoline

measure resistance of CMP, VPWR and PWR GND circuits between PCM harness connector and CMP
sensor harness connector. If resistance measurements are less than 5.0 ohms for each wire, go to next
step. If resistance measurements are 5.0 ohms or more for any wire, repair open circuit.

17) Check CMP Circuit For Short To GND In Harness

Using DVOM, measure resistance between CMP and PWR GND circuits (at either PCM or CMP harness
connector). If resistance(s) is(are) greater than 10 k/ohms, go to next step. If resistance(s) is/are 10k/ohms
or less, repair short circuit.

18) Check For Shorts In PCM

Using DVOM, measure resistance between CMP circuit and both the VPWR and PWR GND circuits at
the CMP harness connector. If resistance(s) is(are) greater than 500 ohms, go to next step. If resistance(s)
is(are) 500 ohms or less, replace PCM.

19) Check CMP Sensor Output During Cranking
Turn ignition switch to OFF position. Disconnect PCM connector(s). Ensure CMP sensor is installed
properly and reconnected. Connect DVOM between CMP and PWR GND circuits at PCM harness
connector. See PCM CONNECTOR IDENTIFICATION and Fig. 203. Set DVOM on DC scale. Using
starter, crank engine in short bursts for at least 10 engine revolutions. If voltage does not switch from less
than 2 volts to more than 8 volts, replace CMP sensor. If voltage switches from less than 2 volts to more
than 8 volts, replace PCM.

TEST DS: AIR CONDITIONING PRESSURE SENSOR

Diagnostic Aids

Perform this test when directed by QUICK TEST. This system test is intended to diagnose:

z

ACP Sensor

z

ACP Wiring Harness Circuits (ACP, VREF & SIG RTN)

z

Powertrain Control Module (PCM)

NOTE:

On vehicles equipped with 150 pin PCMs and Passive Anti-Theft System
(PATS), reconnect the Transmission (T) and Body (B) PCM connectors
only if disconnected. The engine may not crank unless they are
connected. Keep the Engine (E) connector disconnected.

NOTE:

After each service or repair procedure has been completed, reconnect all
components. Clear DTCs and repeat QUICK TEST procedures to ensure all EEC-
V systems are working properly and DTCs are no longer present.

2003 Ford Pickup F150

2003 ENGINE PERFORMANCE Self-Diagnostics - CNG, Flex-Fuel & Gasoline

Fig. 211: Identifying ACP Sensor Circuits & Connector Terminals
Courtesy of FORD MOTOR CO.

Testing

1) For KOEO, KOER & Continuous Memory DTC P1461: Check ACP V PID
This DTC indicates PCM has detected high voltage in ACP circuit. Possible causes for this fault are:

z

ACP Sensor Circuit Short To PWR

z

ACP Circuit Open

z

Faulty Powertrain Control Module (PCM)

z

ACP Circuit Shorted To VREF Or SIG RTN

z

Faulty ACP Sensor

Turn ignition switch to OFF position. Connect scan tool to Data Link Connector (DLC). Turn ignition
switch to ON position. Using scan tool, access ACP V PID from PID/DATA MONITOR & RECORD
menu. If ACP V PID voltage is 4.9 volts or more, go to next step. If ACP V PID voltage is less than 4.9
volts, fault is unable to be duplicated at this time. Go to step 18).

2) Check Voltage Between VREF & SIG RTN Circuits To ACP Sensor

NOTE:

For additional testing information, see DIAGNOSTIC AIDS.

2003 Ford Pickup F150

2003 ENGINE PERFORMANCE Self-Diagnostics - CNG, Flex-Fuel & Gasoline

Turn ignition switch to OFF position. Disconnect ACP sensor connector. Turn ignition switch to ON
position. Using a DVOM, measure voltage between SIG RTN and VREF circuits at ACP sensor harness
connector. See Fig. 211. If voltage is 4-6 volts, go to next step. If voltage is not 4-6 volts, VREF is out of
range or SIG RTN circuit is open. Go to TEST C, step 1).

3) Induce Opposite ACP Signal

Turn ignition switch to ON position. Using scan tool, access ACP V PID from PID/DATA MONITOR &
RECORD menu. If ACP V PID voltage is 4.9 volts or more, go to next step. If ACP V PID voltage is less
than 4.9 volts, replace ACP sensor. Refer to appropriate MANUAL or AUTOMATIC A/C-HEATER
SYSTEMS article in AIR CONDITIONING & HEATING. Start engine and turn A/C on for 15 seconds.
Turn A/C off and repeat

QUICK TEST

.

4) Check ACP Circuit For Short To VREF In Harness

Turn ignition switch to OFF position. Disconnect scan tool from DLC. Disconnect PCM connector(s).
Using a DVOM, measure resistance between ACP and VREF circuits at ACP sensor harness connector.
See Fig. 211. If resistance is more than 10 k/ohms, go to next step. If resistance is 10 k/ohms or less,
repair short to VREF in ACP circuit. Start engine and turn A/C on for 15 seconds. Turn A/C off and
repeat QUICK TEST.

5) Check ACP Circuit For Short To Power In Harness

Turn ignition switch to ON position. Using a DVOM, measure voltage between chassis ground and ACP
circuit at ACP sensor harness connector. See Fig. 211. If voltage is less than one volt, go to next step (LS,
Marauder, Thunderbird and ZX2), or replace PCM (all others). Start engine and turn A/C on for 15
seconds. Turn A/C off and repeat QUICK TEST. If voltage is one volt or more, repair short to VPWR in
ACP circuit. Start engine and turn A/C on for 15 seconds. Turn A/C off and repeat QUICK TEST.

6) Check For Open ACP Circuit In Harness

Turn ignition switch to OFF position. Leave ACP sensor and PCM disconnected. Inspect connector for
loose, damaged or corroded terminals. Repair as necessary. Using a DVOM, measure resistance of ACP
circuit between PCM harness connector and ACP sensor harness connector. See Fig. 211. If resistance is
less than 5 ohms, go to next step. If resistance is 5 ohms or more, repair open in ACP circuit. Start engine
and turn A/C on for 15 seconds. Turn A/C off and repeat QUICK TEST.

7) Check PCM

Reconnect PCM harness connector(s). Leave ACP sensor disconnected. Connect a jumper wire between
ACP and SIG RTN circuits at ACP sensor harness connector. See Fig. 211. Turn ignition switch to ON
position. Using scan tool, access ACP V PID from PID/DATA MONITOR & RECORD menu.

NOTE:

If scan tool is now unable to communicate, replace PCM. Start engine and
turn A/C on for 15 seconds. Turn A/C off and repeat QUICK TEST.

2003 Ford Pickup F150

2003 ENGINE PERFORMANCE Self-Diagnostics - CNG, Flex-Fuel & Gasoline