Ford F150 Pickup. Instruction - part 1497

the sensor is thought to be switching from 0 volts to -1 volts during testing, the PCM will use this input 
and remain in fuel control. Possible causes are: 

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Contaminated HO2S (water, fuel, etc.).  

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Crossed HO2S signal/signal return wiring.  

Check the following areas for cause of contamination:  

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Use Of Unapproved Silicone Sealers  

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Fuel Contaminated By Silicone Additives  

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Excessive Oil Burning (Such As; Rings, Valve Seals And Oil Overfill)  

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Antifreeze (Glycol) Leaking Internally In Engine  

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Lead Contaminated Fuel  

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Short Trip Driving In Cold Weather  

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Use Of Unapproved Cleaning Products  

If contamination exists, repair source of contamination and replace faulty HO2S, oil and filter. Perform 
PCM RESET PROCEDURE under CLEARING CODES under SELF-DIAGNOSTIC SYSTEM. 
Perform DRIVE CYCLES. Ensure HO2S MONITOR PROCEDURE is performed. If contamination 
does not exist and you were directed here to diagnose DTC P0141 or P0161, go to step 30), for all others 
replace PCM. 

28) Verify Wiring Is In Proper Terminal Location 
 
Ensure suspect HO2S harness connector and PCM is disconnected. Using a DVOM, measure resistance 
of HO2S SIG and SIG RTN circuits between PCM harness connector and HO2S harness connector. See 
PCM HO2S, PWR GND & VPWR CIRCUIT TERMINAL IDENTIFICATION table. See Fig. 233. 
If both resistance measurements are less than 5 ohms, replace HO2S. If either resistance measurement is 5 
ohms or more, repair wiring as necessary. 

30) For KOEO, KOER & Continuous Memory DTCs P0135, P0141, P0155 & P0161: HO2S Heater 
Circuit Shorted To GND Or VPWR, Or Open 
These DTCs indicate a short to VPWR, or an open VPWR or GND circuit in HO2S heater circuit causing 
current draw to exceed calibrated limit. HO2S DTC identification is as follows: 

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DTC P0135 Is For HO2S-11  

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DTC P0141 Is For HO2S-12  

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DTC P0147 Is For HO2S-13  

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DTC P0155 Is For HO2S-21  

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DTC P0161 Is For HO2S-22  

NOTE:

A break in step numbering sequence occurs at this point. Procedure skips 
from step 28) to step 30). No test procedures have been omitted.

NOTE:

For additional testing information, see DIAGNOSTIC AIDS.

 

2003 Ford Pickup F150 

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

  

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DTC P0167 Is For HO2S-23  

Refer to illustrations for HO2S identification. See Fig. 230-Fig. 232 . Possible causes are:  

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Short To VPWR Or HO2S Circuit In Harness  

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Water In Connectors  

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Open In GND Or VPWR Circuit  

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Low Battery Voltage  

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Corroded Or Poorly Connected Terminals  

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Damaged HO2S Heater  

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Damaged Powertrain Control Module (PCM)  

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Faulty HO2S Heater  

Inspect HO2S circuit for exposed wiring, water contamination, corrosion and proper assembly. Repair as 
necessary. If HO2S connectors are okay, go to next step. 

31) Perform KOEO On-Demand Self-Test 
 
Start engine and operate at 2000 RPM for one minute. Turn ignition switch to OFF position. Perform 
KOEO ON-DEMAND SELF-TEST. If either DTC P0135, P0141, P0147, P0155, P0161 or P0147 is 
present, go to next step. If specified DTCs are not present, go to step 33). 

32) Check VPWR Voltage To HO2S Harness Connector 
Turn ignition switch to OFF position. Disconnect suspect HO2S harness connector(s). Inspect wiring 
harness for damage and repair as necessary. Turn ignition switch to ON position. Using a DVOM, 
measure voltage between SIG RTN and VPWR circuits at suspect HO2S harness connector. See Fig. 233. 
If voltage is more than 10.5 volts, go to next step. If voltage is 10.5 volts or less, go to TEST B, step 5) 
(LS and Thunderbird), or check VPWR circuit fuse to HO2S heater (all others). If VPWR fuse is blown, 
check VPWR circuit for short to ground. See WIRING DIAGRAMS. Replace fuse and repair circuit as 
necessary. If VPWR circuit fuse is okay, repair open in VPWR circuit. See WIRING DIAGRAMS. 

33) Check HO2S HTR Circuit For Short To PWR GND, SIG RTN Or VPWR 
 
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 between 
suspect HO2S HTR circuit, and PWR GND, SIG RTN and VPWR circuits at suspect HO2S harness 
connector. See PCM HO2S, PWR GND & VPWR CIRCUIT TERMINAL IDENTIFICATION 
table. See Fig. 233. If all resistance measurements are more than 10 k/ohms, go to next step. If any 
resistance measurement is 10 k/ohms or less, repair short in affected circuit. 

34) Check HO2S HTR Circuit For Open In Harness 

NOTE:

If pairs of DTCs P0135 and P0155, P0141 and P0161, or P0147 and P0167 
are retrieved, both HO2S HTR circuits will require testing. DTCs retrieved 
individually, are to be tested individually.

 

2003 Ford Pickup F150 

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

  

 
Leave ignition switch in OFF position and HO2S disconnected. Using a DVOM, measure resistance of 
suspect HO2S HTR circuit between PCM harness connector and HO2S harness connector. See PCM 
HO2S, PWR GND & VPWR CIRCUIT TERMINAL IDENTIFICATION table. See Fig. 233. If 
resistance is 5 ohms or more, repair open circuit or excessive resistance in HO2S HTR circuit. If 
resistance is less than 5 ohms, go to next step. 

35) Check HO2S HTR Resistance 
 
Using a DVOM, measure resistance between HO2S HTR and VPWR circuits at suspect HO2S connector. 
See Fig. 233. If resistance is 3-30 ohms, go to next step. If resistance is not 3-30 ohms, replace HO2S. 

36) Check HO2S Case For Short To VPWR, HTR Or SIG RTN 
 
Using a DVOM, measure resistance between HO2S component case and HO2S HTR, SIG RTN and 
VPWR circuits at HO2S connector. If all resistance measurements are more than 10 k/ohms, replace 
PCM. If any resistance measurement is 10 k/ohms or less, replace HO2S. 

40) For Continuous Memory Only DTCs P1130, P1150, & KOER & Continuous Memory Only 
DTCs P1131, P1132, P1152, P2195, P2196, P2197 & P2198, & For KOEO, KOER & Continuous 
Memory DTC P1151: Upstream HO2S Not Switching 
DTCs P1131, P1151, P2195 and P2197 indicate air/fuel ratio is correcting rich for an overly lean 
condition. DTCs P1132, P1152, P2196 and P2198 indicate air/fuel ratio is correcting lean for an overly 
rich condition. DTCs P1130 and P1150 indicate when an HO2S fails to switch due to a circuit or fuel 
exceeding a calibrated limit. HO2S DTC identification is as follows: 

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DTCs P1130, P1131, P1132, P2195 & P2196 are for HO2S-11.  

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DTCs P1150, P1151, P1152 P2197 & P2198 are for HO2S-12.  

Possible causes are:  

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Fuel System 
 
Excessive fuel pressure, leaking or contaminated fuel injectors, leaking fuel pressure regulator, low 
fuel pressure or engine running out of fuel or vapory recovery system fault. 

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Induction System 
 
Air leaks after MAF sensor, air intake system obstructions, vacuum leaks, PCV system or 
improperly seated engine oil dipstick. 

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EGR System 

NOTE:

A break in step numbering sequence occurs at this point. Procedure skips 
from step 36) to step 40). No test procedures have been omitted.

NOTE:

For additional testing information, see DIAGNOSTIC AIDS.

 

2003 Ford Pickup F150 

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

  

 
Leaking gasket, stuck EGR valve or leaking diaphragm or EVR. 

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Engine Mechanical 
 
Engine oil overfilled, cam timing, cylinder compression or exhaust leaks before or near HO2S.  

Inspect engine for obvious defects in specified systems. Repair as necessary. If no faults are found, go to 
TEST DC, step 25). 

41) For Continuous Memory Only DTC P0171, P0172, P0174 Or P0175: Fuel System At Corrected 
Fuel Trim 
All Continuous Memory ignition and misfire DTCs must be serviced prior to servicing any fuel trim 
DTCs. DTCs P0171, P0172, P0174 and P0175 indicate a concern when adaptive fuel strategy senses a 
lean or rich condition beyond minimum or maximum calibrated limit. Fuel system DTC identification is 
as follows: 

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Bank No. 1 
 
DTCs P0171 (lean), and P0172 (rich). 

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Bank No. 2 
 
DTCs P0174 (lean), and P0175 (rich).  

Possible causes for these faults are:  

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Fuel System 
 
Excessive fuel pressure, leaking or contaminated fuel injectors, leaking fuel pressure regulator, low 
fuel pressure or engine running out of fuel or vapory recovery system fault. 

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Induction System 
 
Air leaks after MAF sensor, air intake system obstructions, vacuum leaks, PCV system or 
improperly seated engine oil dipstick. 

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EGR System 
 
Leaking gasket, stuck EGR valve or leaking diaphragm or EVR. 

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Engine Mechanical 
 
Engine oil overfilled, cam timing, cylinder compression or exhaust leaks before or near HO2S. 

NOTE:

For additional testing information, see DIAGNOSTIC AIDS.

 

2003 Ford Pickup F150 

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