Ford F150 Pickup. Instruction - part 1478

Fig. 194: Identifying CHT Sensor Harness Connector Terminals (All Others) 
Courtesy of FORD MOTOR CO. 

Diagnostic Aids 

Perform this test only when directed by QUICK TEST. This test is intended to diagnose the following:  

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Wiring Harness Circuits (CHT, SIG RTN & VREF)  

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Faulty CHT Sensor  

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Faulty Powertrain Control Module (PCM)  

Testing 

 

2003 Ford Pickup F150 

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

  

1) For KOEO & KOER Only DTC P1116, & For KOEO, KOER & Continuous Memory DTC 
P1288: Check Operation Of CHT Sensor 
DTC P1116 or P1288 indicates CHT sensor is out of self-test range (.3-3.7 volts). Possible causes for 
these faults are: 

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Engine Overheating  

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Low Coolant Level  

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Faulty ECT Sensor  

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Faulty Sensor Connector  

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Poor Thermostat Operation  

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Faulty Powertrain Control Module (PCM)  

Start engine and raise engine speed to 2000 RPM until engine is at normal operating temperature. If 
engine is a no-start or has a stalling concern, go to step 3). Ensure upper radiator hose is hot and 
pressurized. Perform KOER ON-DEMAND SELF-TEST. Check for DTC P1116 or P1288. If DTC 
P1116 or P1288 is not present, engine temperature was not stabilized. Service any other DTCs and repeat 
QUICK TEST. For LS and Thunderbird, if DTC P1116 or P1288 is present, go to step 3). For all others, 
go to next step. 

2) Check VREF Circuit Voltage At TP Sensor 
 
Turn ignition switch to OFF position. Disconnect TP sensor connector. Turn ignition switch to ON 
position. Using a DVOM, measure voltage between VREF and SIG RTN circuits at TP sensor harness 
connector. See Fig. 163-Fig. 166 . If voltage is 4-6 volts, VREF voltage is okay. Reconnect TP sensor 
and go to next step. If voltage is not 4-6 volts, go to TEST C, step 1). 

3) Check Resistance Of CHT Sensor With Engine Off 
 
Turn ignition switch to OFF position. Disconnect CHT sensor connector. Using a DVOM, measure 
resistance between CHT sensor terminals. See Fig. 193 and Fig. 194 . See CHT SENSOR 
SPECIFICATIONS table. If resistance is not as specified, replace CHT sensor. If resistance is as 
specified and engine is a no-start or engine has a stalling concern, see appropriate symptom under 
SYMPTOMS in TROUBLE SHOOTING - NO CODES - CNG, FLEX-FUEL & GASOLINE article. If 
resistance is as specified and engine starts and does not stall, go to next step. 

4) Check Resistance Of CHT Sensor With Engine Running 
 
Start engine. Ensure engine is at normal operating temperature. Raise engine speed to 2000 RPM for 2 
minutes. Using a DVOM, measure resistance between CHT sensor terminals. See CHT SENSOR 
SPECIFICATIONS table. If resistance is as specified, replace PCM. If resistance is not as specified, 
replace CHT sensor. 

NOTE:

For additional testing information, see DIAGNOSTIC AIDS.

NOTE:

Engine coolant temperature must be more than 50°F (10°C) to pass KOEO 
self-test and more than 180°F (82°C) to pass KOER self-test.

 

2003 Ford Pickup F150 

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

  

5) For KOEO & KOER Only DTCs P1289 & P1290: Check CHT V PID Voltage 
DTC P1289 indicates that CHT sensor circuit is open. DTC P1290 indicates CHT sensor circuit is 
shorted. Possible causes for these faults are: 

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Open Or Grounded CHT Circuit  

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Faulty CHT Sensor  

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Faulty CHT Sensor Connector  

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Faulty Powertrain Control Module (PCM)  

Turn ignition switch to OFF position. Connect scan tool to Data Link Connector (DLC). Turn ignition 
switch to ON position. Using scan tool, access CHT V PID from PID/DATA MONITOR & RECORD 
menu. If CHT V PID voltage is less than .2 volt, go to next step. If CHT V PID voltage is .2 volt or more, 
go to step 7). 

6) Check For Grounded Circuit 
 
Disconnect CHT sensor connector. Using scan tool, access CHT V PID from PID/DATA MONITOR & 
RECORD menu. If CHT V PID reading is more than 4.6 volts, replace CHT sensor. If CHT V PID 
voltage is 4.6 volts or less, go to step 21). 

7) Check For Open Harness 
 
Disconnect CHT sensor connector. Connect a jumper wire between CHT and SIG RTN circuits at CHT 
sensor harness connector. Turn ignition switch to ON position. Using scan tool, access CHT V PID from 
PID/DATA MONITOR & RECORD menu. 

If CHT V PID voltage is less than .2 volt, replace CHT sensor. If PID voltage is .2 volt or more, remove 
jumper wire and go to step 11). 

10) For KOEO & KOER Only DTC P0118: Simulate Opposite Signal To PCM 
This DTC indicates CHT sensor signal is more than self-test maximum of 4.6 volts, or -58°F (-50°C). 
Possible causes for this fault are: 

NOTE:

For additional testing information, see DIAGNOSTIC AIDS.

NOTE:

If a scan tool communication concern exists, remove jumper wire and go 
to step 12).

NOTE:

A break in step numbering sequence occurs at this point. Procedure skips 
from step 7) to step 10). No test procedures have been omitted.

NOTE:

For additional testing information, see DIAGNOSTIC AIDS.

NOTE:

If a scan tool communication concern exists, remove jumper wire and go 
to step 12).

 

2003 Ford Pickup F150 

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

  

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Open Circuit  

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Sensor Signal Shorted To Power  

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Faulty CHT Sensor Or Connector  

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Faulty PCM  

Turn ignition switch to OFF position. Disconnect CHT sensor connector. Inspect connector for loose, 
damaged or corroded terminals. Repair as necessary. Connect a jumper wire between CHT and SIG RTN 
circuits at CHT sensor harness connector. Connect scan tool to Data Link Connector (DLC). Turn 
ignition switch to ON position. 

Using scan tool, access CHT V PID from PID/DATA MONITOR & RECORD menu. If CHT V PID 
voltage is less than .2 volt, replace CHT sensor. If CHT V PID voltage is .2 volt or more, remove jumper 
wire and go to next step. 

11) Check CHT Signal & SIG RTN Circuits For Open 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 CHT and 
SIG RTN circuits between PCM harness connector and CHT sensor harness connector. See Fig. 193 or 
Fig. 194 . If both resistance measurements are less than 5 ohms, replace PCM. If either resistance 
measurement is 5 ohms or more, repair open in affected circuit. 

12) Check CHT Circuit For Short To VREF 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 between CHT 
and VREF circuits at PCM harness connector (both VREF circuits on 150-pin PCM). See WIRING 
DIAGRAMS. See PCM CONNECTOR IDENTIFICATION. If resistance is more than 10 k/ohms, 
replace PCM. If resistance is 10 k/ohms or less, locate and repair short circuit to VREF. 

20) For KOEO & KOER Only DTC P0117: Simulate Opposite Signal To PCM 
DTC P0117 indicates CHT sensor signal is less than self-test minimum of .2 volt or 250°F (121°C). 
Minimum signal for CHT sensor is .2 volt. Possible causes for this fault are: 

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Grounded Circuit In Harness  

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Faulty CHT Sensor Or Connector  

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Faulty PCM  

Turn ignition switch to OFF position. Disconnect CHT sensor connector. Inspect connector for loose, 
damaged or corroded terminals. Repair as necessary. Connect scan tool to Data Link Connector (DLC). 

NOTE:

A break in step numbering sequence occurs at this point. Procedure skips 
from step 12) to step 20). 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