Ford F150 Pickup. Instruction - part 1578

12) Network Test Results: Circuit 914BUS (+) & Circuit 915BUS (-) 
 
Proceed as follows for appropriate message displayed: 

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If only BUS(+) CKT 914=ALL MODULE NO RESP/NOT EQUIP message is displayed, go to 
next step.  

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If only BUS(-) CKT 915=ALL MODULE NO RESP/NOT EQUIP message is displayed, go to step 
16).  

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If both BUS(+) CKT 914 and BUS(-) CKT 915=ALL MODULE NO RESP/NOT EQUIP messages 
are displayed, go to step 22).  

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If BUS(+) CKT 914=SOME MODULE NO RESP/NOT EQUIP or PCM: NO RESPONSE ON 
BUS(+) CKT 914 message is displayed, go to step 15).  

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If BUS(-) CKT 915=SOME MODULE NO RESP/NOT EQUIP or PCM: NO RESPONSE ON 
BUS(-) CKT 915 message is displayed, go to step 18).  

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If both BUS(+) CKT 914 and BUS(-) CKT 915=SOME MODULE NO RESP/NOT EQUIP or 
PCM: NO RESPONSE ON BUS(+) & BUS(-) messages are displayed, go to step 23).  

13) Check BUS(+) CKT 914 For Short To Ground In Harness 
 
Turn ignition switch to OFF position. Disconnect PCM connector(s). Inspect connector for loose, 
damaged or corroded terminals. Repair as necessary. Using a DVOM, measure resistance of BUS(+) 
CKT 914 circuit between chassis ground and PCM harness connector. See PCM CONNECTOR 
IDENTIFICATION and Fig. 355 or Fig. 356 . If resistance is more than 50 ohms, go to next step. If 
resistance is 50 ohms or less, repair short to ground in BUS(+) CKT 914 circuit or associated modules. 
See appropriate MODULE COMMUNICATIONS NETWORK article in ACCESSORIES & 
EQUIPMENT for further diagnosis. 

14) Check BUS(+) CKT 914 For Short To B+ In Harness 
 
Turn ignition switch to ON position. Using a DVOM, measure voltage between chassis ground and BUS
(+) CKT 914 circuit at PCM harness connector. If voltage is one volt or less, go to next step. If voltage is 
more than one volt, repair short to B+ in BUS(+) CKT 914 circuit or associated modules. See appropriate 
MODULE COMMUNICATIONS NETWORK article in ACCESSORIES & EQUIPMENT for further 
diagnosis. 

15) Check DLC BUS(+) CKT 914 For Open In Harness 
 
Turn ignition switch to OFF position and disconnect PCM connector(s), if not done previously. Using a 
DVOM, measure resistance of BUS(+) CKT 914 circuit between PCM harness connector and DLC. See 
PCM CONNECTOR IDENTIFICATION and Fig. 355 or Fig. 356 . If resistance is less than 5 ohms, 
go to next step. If resistance is 5 ohms or more, repair open in BUS(+) CKT 914 circuit to DLC. 

16) Check BUS(-) CKT 915 For Short To Ground In Harness 
 
Disconnect PCM if not done previously. Using a DVOM, measure resistance of BUS(-) CKT 915 circuit 
between PCM harness connector and negative battery terminal. If resistance is more than 50 ohms, go to 

 

2003 Ford Pickup F150 

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

  

next step. If resistance is 50 ohms or less, repair short to ground in BUS(-) CKT 915 circuit or associated 
modules. See appropriate MODULE COMMUNICATIONS NETWORK article in ACCESSORIES & 
EQUIPMENT for further diagnosis. 

17) Check BUS(-) CKT 915 For Short To B+ In Harness 
 
Turn ignition switch to ON position. Using a DVOM, measure voltage between chassis ground and BUS
(-) CKT 915 circuit at PCM harness connector. See PCM CONNECTOR IDENTIFICATION and Fig. 
355 or Fig. 356 . If voltage is 6 volts or less, go to next step. If voltage is more than 6 volts, repair a short 
to B+ in BUS(-) CKT 915 circuit or associated modules. See appropriate MODULE 
COMMUNICATIONS NETWORK article in ACCESSORIES & EQUIPMENT for further diagnosis. 

18) Check DLC BUS(-) CKT 915 For Open In Harness 
 
Turn ignition switch to OFF position. Using a DVOM, measure resistance of BUS(-) CKT 915 between 
PCM harness connector and DLC. See PCM CONNECTOR IDENTIFICATION and Fig. 355 or Fig. 
356 . If resistance is less than 5 ohms, go to next step. If resistance is 5 ohms or more, repair open in BUS
(-) CKT 915 circuit to DLC. 

19) Check Power Relay VPWR To PCM 
 
Turn ignition switch to OFF position. Disconnect PCM connector(s). Turn ignition switch to ON position. 
Using a DVOM, measure voltage between VPWR and GND circuits at PCM harness connector. See 
PCM CONNECTOR IDENTIFICATION and Fig. 168-Fig. 170 . See PCM PWR GND, SIG RTN & 
VREF TERMINAL IDENTIFICATION table. If voltage is 10.5 volts or less, turn ignition switch to 
OFF position. Repair VPWR circuit from PCM power relay to PCM. If voltage is more than 10.5 volts, 
go to next step (for scan tools with Data Link Diagnostic Network Test capability), or for scan tools 
without Data Link Diagnostic Network Test capability, see appropriate MODULE COMMUNICATIONS 
NETWORK article in ACCESSORIES & EQUIPMENT for further diagnosis. If after completing 
MODULE COMMUNICATIONS NETWORK diagnosis and you are directed back here, replace PCM. 

20) Power Take Off Applications 
 
If vehicle is equipped with Power Take Off (PTO), go to next step. If vehicle is not equipped with PTO, 
replace PCM. 

21) Check PTO ON/OFF Input 
 
Turn ignition switch to ON position. While cycling PTO switch/actuator, measure voltage between 
chassis ground and PTO circuit at PCM harness connector terminal No. 4. If voltage is more than one volt 
with PTO on, and less than one volt with PTO off, PTO circuit is okay. Replace PCM. If voltage is not as 
specified, PTO circuit has a fault. Go to TEST FB, step 

1)

 for PTO circuit fault diagnosis. 

22) Check For BUS(+) CKT 914 Shorted To BUS(-) CKT 915 
 
Turn ignition switch to OFF position. Disconnect PCM connector(s). Using a DVOM, measure resistance 
between BUS(+) CKT 914 and BUS(-) CKT 915 circuits at PCM harness connector. See PCM 

 

2003 Ford Pickup F150 

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

  

CONNECTOR IDENTIFICATION and Fig. 355 or Fig. 356 . If resistance is more than 5 ohms, go to 
next step. If resistance is 5 ohms or less, repair short between BUS(+) CKT 914 and BUS(-) CKT 915 
circuits or in associated modules. See appropriate MODULE COMMUNICATIONS NETWORK article 
in ACCESSORIES & EQUIPMENT for further diagnosis. 

23) Check For Open BUS(+) CKT 914 Or BUS(-) CKT 915 In Harness 
 
Using a DVOM, measure resistance of BUS(+) CKT 914 and BUS(-) CKT 915 circuits between PCM 
harness connector and DLC. See PCM CONNECTOR IDENTIFICATION and Fig. 355 or Fig. 356 . 
If either resistance is 5 ohms or more, repair open in BUS(+) CKT 914 or BUS(-) CKT 915 between DLC 
and all associated modules. If both resistance measurements are less than 5 ohms, go to step 19) (if scan 
tool has DATA LINK DIAGNOSTIC NETWORK TEST capability, or if scan tool does not have DATA 
LINK DIAGNOSTIC NETWORK TEST capability, see appropriate MODULE COMMUNICATIONS 
NETWORK article in ACCESSORIES & EQUIPMENT for further diagnosis. If MODULE 
COMMUNICATIONS NETWORK article diagnostics are completed and you are directed back to SELF-
DIAGNOSTICS - CNG, FLEX-FUEL & GASOLINE article, replace PCM. 

30) Check VREF Voltage To FRP Sensor 
 
The purpose of this test step is to determine if the PCM is powering up by checking the VREF from the 
PCM. Turn ignition switch to OFF position. Disconnect Fuel Rail Pressure (FRP) sensor. Turn ignition 
switch to ON position. Using a DVOM, measure voltage between VREF and SIG RTN circuits at the 
FRP sensor harness connector. See Fig. 187. If the voltage is 4.0-6.0 volts, voltage is okay. Go to next 
step. If the voltage is 4.0-6.0 volts, voltage is not okay. Go to TEST C, step 1). 

31) Check B+ Voltage To Data Link Connector (DLC) 
 
Disconnect scan tool from DLC. Inspect the DLC for damage. Repair as necessary. Using DVOM, 
measure voltage between B+ circuit cavity at the DLC and ground. If voltage is greater than 10.5 volts, 
go to next step. If voltage is 10.5 volts or less, repair open in DLC B+ circuit. 

32) Check DLC Chassis Ground Circuit For Open In Harness 
 
Using a DVOM, measure resistance between chassis ground circuit at the DLC and chassis ground. If 
resistance is less than 5.0 ohms, go to next step. If resistance is 5.0 ohms or more, repair open circuit. 

33) Check DLC PWR GND Circuit For Open In Harness 
 
Using a DVOM, measure resistance between PWR GND circuit at the DLC and battery negative 
terminal. If resistance is less than 5.0 ohms, go to next step. If resistance is 5.0 ohms or more, repair open 
circuit. 

34) Check For HS-CAN(+) Short To HS-CAN(-) 
 
Turn ignition switch to OFF position. Disconnect PCM. Using a DVOM, measure resistance between HS-
CAN(+) and HS-CAN(-) circuits at the DLC harness connector. If resistance is greater than 5.0 ohms, go 
to next step. If resistance is 5.0 ohms or less, go to step 39). 

 

2003 Ford Pickup F150 

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

  

35) Check For Open HS-CAN(+/-) Circuits In Harness 
 
Using a DVOM, measure resistance of HS-CAN(+) circuit between PCM harness connector pin and HS-
CAN(+) circuit at the DLC. Measure resistance of HS-CAN(-) circuit between PCM harness connector 
pin and HS-CAN(-) circuit at the DLC. If both resistances are less than 5.0 ohms, go to next step. If either 
resistance is 5.0 ohms or more, repair open circuit. 

36) Check HS-CAN(+/-) Circuits For Short To B+ In Harness 
 
Turn ignition switch to ON position. Using a DVOM, measure voltage between HS-CAN(+) circuit at the 
PCM harness connector pin and chassis ground. Measure voltage between HS-CAN(-) circuit at the PCM 
harness connector pin and chassis ground. If either voltage is greater than 6.0 volts, go to step 39). If both 
voltages are 6.0 volts or less, go to next step. 

37) Check HS-CAN(+/-) Circuits For Short To Ground In Harness 
 
Turn ignition switch to OFF position. Using a DVOM, measure resistance of HS-CAN(+) circuit between 
PCM harness connector pin and chassis ground. Measure resistance of HS-CAN(-) circuit between PCM 
harness connector pin and chassis ground. If both resistances are greater than 50 ohms, replace PCM. If 
either resistance is 50 ohms or less, go to step 39). 

39) Verify If HS-CAN(+/-) Is Shorted In Harness Or Another Module 
 
Determine which, if any, modules are connected to the HS-CAN network. See appropriate WIRING 
DIAGRAMS. If no other modules are connected to the HS-CAN network, repair short circuit. If other 
modules are connected to the HS-CAN network, one at a time, disconnect the modules associated with 
HS-CAN network. After disconnecting each module, again test for short circuit. Repeat until each 
associated module has been disconnected or the short circuit has been eliminated. If the short circuit 
remained after all associated modules were disconnected, repair short circuit in wiring. If short circuit is 
associated with a particular module, see appropriate diagnostic article to repair that module.  

TEST QB: KOEO DTC P0603 OR KOEO, KOER & CONTINUOUS MEMORY DTC P1633 

Diagnostic Aids 

Perform this test when instructed during QUICK TEST or if directed by other test procedures. This test is used 
to diagnose the following:  

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Battery Terminal Condition  

NOTE:

A break in step numbering sequence occurs at this point. Procedure skips 
from step 37) to step 39). No test procedures have been omitted.

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