Ford F150 Pickup. Instruction - 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