Ford F150 Pickup. Instruction - part 1534

cylinders, go to next step. If spark is missing from one cylinder, check spark plug wire and spark plug 
where missing cylinder pattern exists. Measure resistance of spark plug wire. Spark plug wire resistance 
should be 7 k/ohms or less per foot. Measure resistance of spark plug. Spark plug resistance should be 2-
20 k/ohms. Repair as necessary. Perform DRIVE CYCLES. Ensure MISFIRE & FUEL MONITOR 
PROCEDURES are performed to verify repair. 

Fig. 283: Identifying One Missing Spark Pattern 
Courtesy of FORD MOTOR CO. 

7) Check For High Spark Plug Firing Voltage 
 
Observe scope pattern and check for high spark firing voltage and pattern. See Fig. 284. If spark plug 
firing voltage is 15 kilovolts or less, go to next step. If average spark plug firing voltage is more than 15 
kilovolts, check spark plug wires and spark plugs on affected cylinders. Measure resistance of spark plug 
wires. Spark plug wire resistance should be 7 k/ohms or less per foot. Measure resistance of spark plugs. 
Spark plug resistance should be 2-20 k/ohms. Repair as necessary. Perform DRIVE CYCLES. Ensure 
MISFIRE & FUEL MONITOR PROCEDURES are performed to verify repair. 

 

2003 Ford Pickup F150 

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

  

Fig. 284: Identifying High Spark Plug Firing Voltage 
Courtesy of FORD MOTOR CO. 

8) Check For Low Spark Plug Firing Voltage 
 
Observe scope pattern and check for low spark plug firing voltage and pattern. See Fig. 285. If spark plug 
firing voltage is inconsistent (low on one or more cylinders), go to next step. If spark plug firing voltage 
is consistently low or a sloped spark line is present in one or more cylinders, check spark plug wires and 
spark plugs on affected cylinders. Measure resistance of spark plug wires. Spark plug wire resistance 
should be 7 k/ohms or less per foot. Measure resistance of spark plugs. Spark plug resistance should be 2-
20 k/ohms. Repair as necessary. Perform DRIVE CYCLES. Ensure MISFIRE & FUEL MONITOR 
PROCEDURES are performed to verify repair. 

 

2003 Ford Pickup F150 

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

  

Fig. 285: Identifying Low Spark Plug Firing Voltage 
Courtesy of FORD MOTOR CO. 

9) Check For Uneven Spark Plug Firing Voltage Between Cylinders 
 
Observe scope pattern and check for uneven spark plug firing voltage and pattern. See Fig. 286. If spark 
plug firing voltage variation is more than 6 kilovolts, check spark plug wires and spark plugs on affected 
cylinders. Measure resistance of spark plug wires. Spark plug wire resistance should be 7 k/ohms or less 
per foot. Measure resistance of spark plugs. Spark plug resistance should be 2-20 k/ohms. Repair as 
necessary. Perform DRIVE CYCLES. Ensure MISFIRE & FUEL MONITOR PROCEDURES are 
performed to verify repair. If spark plug firing voltage variation is 6 kilovolts or less, fault is unable to be 
duplicated at this time. Go to TEST Z, step 1). 

 

2003 Ford Pickup F150 

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

  

Fig. 286: Checking For Uneven Spark Plug Firing Voltage Between Cylinders 
Courtesy of FORD MOTOR CO. 

15) DTC P0301-P0310: Misfire On Cylinders No. 1-10 
 
If DTC P0301, P0302, P0303, P0304, P0305, P0306, P0307, P0308, P0309 or P0310 is present, go to 
next step. If specified DTCs are not present, go to step 17). 

16) Check For Spark At Cylinder(s) Indicated By DTC(s) 
 
Disable Inertia Fuel Shutoff (IFS) switch. Disconnect ignition coil(s) from spark plug(s). Connect Air 
Gap Spark Tester (303-D037) to suspect coil(s). Check for spark at cylinder(s) while cranking engine. If 
Blue-White spark is present, turn ignition switch to OFF position and go to step 18). If Blue-White spark 
is not present, check coil boots of missing cylinders. Replace as necessary. If boots are okay, measure 
resistance of spark plug(s). If resistance is not 2-20 k/ohms, replace affected spark plug(s) and go to 
TEST JF, step 1). 

17) Check For Spark At All Cylinders 
 
Disable Inertia Fuel Shutoff (IFS) switch. Disconnect ignition coil(s) from spark plug(s). Install Air Gap 

NOTE:

A break in step numbering sequence occurs at this point. Procedure skips 
from step 9) to step 15). No test procedures have been omitted.

 

2003 Ford Pickup F150 

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