Ford F150 Pickup. Instruction - part 1501

For HO2S connector terminals, see Fig. 233. 

Fig. 235: Identifying Natural Gas Module Circuits & Connector Terminals 
Courtesy of FORD MOTOR CO. 

HO2S-21 HTR (Left Upstream)

94

HO2S-22 SIG (Left Downstream)

61

HO2S-22 HTR (Left Downstream)

96

HO2S SIG RTN

91

HO2S VPWR

71

 

2003 Ford Pickup F150 

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

  

Fig. 236: Identifying Fuel Tank Pressure Sensor Connector Terminals 
Courtesy of FORD MOTOR CO. 

Testing 

30) For KOEO, KOER & Continuous Memory DTCs P0135, P0141, P0155 Or P0161: HO2S HTR 
SIG Circuit Is Open, Shorted To Ground Or VPWR, Or Excessive Current Draw 
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: 

z

DTC P0135 Refers To Upstream HO2S-11  

z

DTC P0141 Refers To Downstream HO2S-12  

z

DTC P0155 Refers To Upstream HO2S-21  

z

DTC P0161 Refers To Downstream HO2S-22  

Refer to illustration for HO2S identification. See Fig. 231. Possible causes are:  

z

Short To VPWR Or HO2S Circuit  

z

Water In Connectors  

z

Open In GND Or VPWR Circuit  

z

Low Battery Voltage  

z

Corroded Or Poorly Connected Terminals  

z

Damaged HO2S Heater  

z

Damaged Powertrain Control Module (PCM)  

z

Faulty HO2S Heater  

Inspect HO2S connectors for loose, damaged or corroded terminals. Repair as necessary. If HO2S 

NOTE:

Test procedure begins with 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

  

connectors are okay, go to next step. 

31) Perform KOEO 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 DTCs P0135, P0141, P0155 and/or P0161 are present, go to 
next step. If specified DTCs are not present, fault may be intermittent. Go to TEST Z, step 1). 

32) Check VPWR Voltage To HO2S Harness Connector 
Turn ignition switch to OFF position. Disconnect suspect HO2S connector. 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 
10.5 volts or less, go to next step. If voltage is more than 10.5 volts, go to step 34). 

33) Check VPWR Circuit For Open In Harness 
 
Turn ignition switch to OFF position. Disconnect PCM connector. Inspect connector for loose, damaged 
or corroded terminals. Repair as necessary. Using a DVOM, measure resistance of VPWR circuit 
between PCM harness connector and HO2S harness connector. See NGV HO2S PCM TERMINAL 
IDENTIFICATION table. See PCM CONNECTOR IDENTIFICATION and Fig. 233. If resistance is 
less than 5 ohms, go to next step. If resistance is 5 ohms or more, check VPWR circuit fuse. If fuse is 
okay, repair open in VPWR circuit. 

34) Check HO2S HTR Resistance 
 
Turn ignition switch to OFF position. Using a DVOM, measure resistance of HO2S HTR GND and 
VPWR terminals at HO2S connector. See Fig. 233. If resistance is 3-30 ohms, go to next step. If 
resistance is not 3-30 ohms, replace faulty HO2S. 

35) Check HO2S Case For Short To HTR GND Or VPWR 
 
Using a DVOM, measure resistance between HO2S case and HO2S HTR GND and VPWR terminals at 
HO2S connector. See Fig. 233. If both resistance measurements are more than 10 k/ohms, go to next step. 
If either resistance measurement is 10 k/ohms or less, replace faulty HO2S. 

36) Check For Shorts To Other Grounds Or VPWR In HO2S HTR GND Harness Circuits 
 
Disconnect PCM connector. Using a DVOM, measure resistance between HO2S HTR circuit, and PWR 
GND, SIG RTN and VPWR circuits at suspect HO2S harness connector. 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 between affected circuits. 

37) Check HO2S HTR GND For Open In Harness 

NOTE:

If pairs of DTCs P0135 and P0155, or P0141 and P0161 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

  

 
Using a DVOM, measure resistance of HO2S HTR GND circuit between suspect HO2S harness 
connector and PCM harness connector. See NGV HO2S PCM TERMINAL IDENTIFICATION table. 
See PCM CONNECTOR IDENTIFICATION and Fig. 233. If resistance is less than 5 ohms, replace 
PCM. If resistance is 5 ohms or more, repair open or excessive resistance in HTR GND circuit in wiring 
harness. 

40) For Continuous Memory Only DTCs P1130, P1150, & For KOER & Continuous Memory 
DTCs P1131, P1132, P1151, P1152, P2195, P2196, P2197 Or P2198: Upstream HO2S Not Switching
Continuous Memory DTCs P1130 and P1150 indicate when an HO2S fails to switch due to a circuit or 
fuel at or exceeding a calibrated limit. KOER and Continuous Memory DTCs P1131, P1132, P1151, 
P1152, P2195, P2196, P2197 and P2198 indicate a concern when fuel control system does not detect 
HO2S switching for a calibrated time. DTCs P1130, P1131, P1132, P2195 and P2196 refer to HO2S-11. 
DTCs P1150, P1151, P1152, P2197 and P2198 refer to HO2S-21. Possible causes for these faults are: 

z

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. 

z

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

z

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

z

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 
DTCs P0171, P0172, P0174 and P0175 indicate a concern when adaptive fuel strategy senses a lean or 
rich condition beyond the minimum or maximum calibrated limit. DTCs P0171 (lean) and P0172 (rich) 

NOTE:

A break in step numbering sequence occurs at this point. Procedure skips 
from step 37) to step 40). No test procedures have been omitted.

NOTE:

For additional testing information, see DIAGNOSTIC AIDS.

NOTE:

For additional testing information, see DIAGNOSTIC AIDS.

 

2003 Ford Pickup F150 

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