Mechanics

TROUBLE CODE P0125 ( TC) COLD STARTS, ENGINE FIRES UP THEN IDLES LOW THEN RETURNS TO NORMAL IDLE, AND THEN WHEN PUT IN DRIVE DOES SAME THING.

2001 Lincoln Town Car • 127 miles

I know the code has something to do with thermostat, low coolant, or coolant temp sensor, but does it relate to this? When I start the car cold, it fires up and then idles really low for about a second and then pops back up to regular idle. Then when I put it in drive and have my foot on the brake, the car does the same thing, but sometimes does it more than once. After this happens and it returns to normal idle, it drives fine. What would be the cause of this? Would this be related to the p0125 code? Any help is appreciated.
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Jross2828
January 2, 2012.



According to our reference, the P0125 refers to a "Continuous Memory Only"
ENGINE CONTROL SYSTEM - SELF-DIAGNOSTICS - EEC-V - CNG & GASOLINE. Page 1 of 10
TEST DA: TEMPERATURE SENSOR TEST (IAT, ECT & EOT)

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.
Diagnostic Aids

Perform this test only when directed by QUICK TEST. Ambient air temperature must be at least 50°F (10°C) to receive valid input from Intake Air Temperature (IAT) sensor. Engine coolant temperature and
engine oil temperature must be more than 50°F (10°C) to pass KOEO SELF-TEST. Engine coolant temperature must be more than 180°F (82°C) and engine oil temperature must be more than 150°F (66°
C) to pass KOER SELF-TEST. Voltage values in this test are based on a 5-volt VREF signal. Values may vary up to 15 percent due to sensor and VREF variations.
This system test is intended to diagnose the following components and circuits: ? Intake Air Temperature (IAT) Sensor Or Integrated Intake Air Temperature (IAT) Sensor ? Engine Coolant Temperature (ECT) Sensor
? Engine Oil Temperature (EOT) Sensor
? Wiring Harness Circuits (IAT, ECT, EOT & SIG RTN) ? Powertrain Control Module (PCM)
To prevent replacing good components, ensure the following non-EEC areas or components are not cause of problem: ? Coolant Level Low
? Cooling System, Water Pump Or Fan ? Engine Operating Temperature
? Engine Oil Level Low ? Thermostat
? Air Cleaner Duct
? Ambient Temperature
NOTE: On some models, IAT sensor is part of Mass Airflow (MAF) sensor
assembly. If all 6 terminals of MAF sensor connector are being used, IAT sensor is integral to MAF sensor. See WIRING DIAGRAMS article.
NOTE: Proceed to DTC testing steps listed in FAULT CODE SETTING CONDITION table of fault code setting condition.
FAULT CODE SETTING CONDITION
Fault Code P0112
P0113
KOEO DA20
DA10
KOER DA20
DA10
Continuous Memory DA90
DA90

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P0116 (ECT Sensor) 1 P0117 (ECT Sensor) 1
P0118 (ECT Sensor) 1 P0125
P1112
P1116 (ECT Sensor) 1 P1117 (ECT Sensor) 1
P1183 P1184
() For Engines equipped with Cylinder Head Temperature Sensor (CHT) see FAULT CODE SETTING CONDITION

DA20 DA10

DA1

DA20 DA10

DA1

DA80 DA90
DA90 DA100
DA90

DA90 DA111
DA110
1) DTC P1116: Check Operation Of ECT Sensor

This DTC indicates sensor is out of self-test range. Correct range for measurement is.3-3.7 volts. Check for following possible causes: ? Low Coolant Level
? Faulty Harness Or Connector ? Faulty Sensor
? Faulty PCM
If directed here because engine is a no-start, go to step 3). If vehicle has a stalling problem, go to appropriate symptom under SYMPTOMS in TROUBLE SHOOTING - NO CODES - EEC-V -
CNG & GASOLINE article. Start and run engine at 2000 RPM until engine reaches normal operating temperature. Ensure upper radiator hose is hot and pressurized. Repeat KOER ON-
DEMAND SELF-TEST. If DTC P1116 is present, go to next step. If DTC P1116 is not present, engine was not at closed loop operating conditions when KOER ON-DEMAND SELF-TEST was
originally performed. Repair any other DTCs that are present.
2) Check VREF Circuit Voltage To TP Sensor

Turn ignition switch to OFF position. Disconnect Throttle Position (TP) sensor. Turn ignition switch to ON position. Using a DVOM, measure voltage between VREF and SIG RTN terminals
at TP sensor harness connector. See Fig. 5-Fig. 8. If voltage is 4-6 volts, reconnect TP sensor and go to next step. If voltage is not 4-6 volts, go to TEST C, step 1).
3) Check ECT Sensor Resistance With Engine Off

Turn ignition switch to OFF position. Disconnect ECT sensor. Using a DVOM, measure resistance between ECT sensor SIG and SIG RTN circuit terminals. See IAT, ECT & EOT
SENSOR SPECIFICATIONS table. See Fig. 14. If resistance is not as specified, replace faulty ECT sensor. If resistance is as specified, perform following step as applicable: ? For diagnosing vehicles with an ECT sensor related fault, or engine is a no-start, DO NOT service DTC P1116 at this time. See NO START/NORMAL CRANK symptom under
SYMPTOMS in TROUBLE SHOOTING - NO CODES - EEC-V - CNG & GASOLINE article.
? For diagnosing vehicles with cooling fan problems or engine cooling problems, DO NOT

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service DTC P1116 at this time. Service next DTC. If no other DTCs are present, repair by symptom. See SYMPTOMS in TROUBLE SHOOTING - NO CODES - EEC-V - CNG &
GASOLINE article.
? For vehicles with no other fault conditions or DTCs, go to next step.
Fig. 14: Identifying Engine Coolant Temperature (ECT) Sensor Circuits & Connector Terminals
Courtesy of FORD MOTOR CO.
Fig. 15: Identifying Engine Oil Temperature (EOT) Sensor Circuits & Connector Terminals (LS)
Courtesy of FORD MOTOR CO.
Fig. 16: Identifying Intake Air Temperature (IAT) Sensor Circuits & Connector Terminals (Continental, Cougar 2.5L, Crown Victoria, Expedition, F150 Pickup, Grand Marquis, LS,
Mustang 4.6L & Ranger 2.5L) Courtesy of FORD MOTOR CO.
Fig. 17: Identifying MAF With Integrated Intake Air Temperature (IAT) Sensor Circuits & Connector Terminals (Cougar 2.0L & Focus)
Courtesy of FORD MOTOR CO.
Fig. 18: Identifying MAF With Integrated Intake Air Temperature (IAT) Sensor Circuits & Connector Terminals (All Other Models)
Courtesy of FORD MOTOR CO.
NOTE: Engine must be at normal operating temperature before taking temperature sensor measurements.
NOTE: A break in step numbering sequence occurs at this point. Procedure skips from step 4) to step 10). No test procedures have been
omitted.
4) Check ECT Sensor Resistance With Engine Running
Reconnect all connectors. Start engine and operate at 2000 RPM for 2 minutes. Turn ignition switch to OFF position. Disconnect ECT sensor. Using a DVOM, measure resistance between
ECT sensor SIG and SIG RTN circuit terminals. See IAT, ECT & EOT SENSOR SPECIFICATIONS table. See Fig. 14. If resistance is not as specified, replace faulty ECT
sensor. If resistance is as specified, replace PCM.

(1)
IAT, ECT & EOT SENSOR SPECIFICATIONS
Temperature °F (°C) 50 (10)
68 (20) 86 (30)
104 (40) 122 (50)
140 (60)
Volts 3.51
3.07 2.60
2.13 1.70
1.33
k/Ohms 58.75
37.30 24.27
16.15 10.97
7.70

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158 (70) 176 (80)
194 (90) 212 (100)
230 (110) 248 (120)
(1) Values may vary by 15 percent.
1.02 0.78
0.60 0.46
0.35 0.27
5.37 3.84
2.80 2.07
1.55 1.18
10) DTC P0118 Or P0113: Check Voltage Between VREF & SIG RTN

DTC P0118 (ECT) or P0113 (IAT) indicates ECT or IAT sensor signal is more than self-test maximum. Maximum measurement should be 4.6 volts at -58°F (-50°C). Check for following
possible causes: ? Open Circuit In Harness Or Connector ? Sensor Signal Short To Power
? Faulty Sensor ? Faulty PCM
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
harness connector. See Fig. 5-Fig. 8. If voltage is 4-6 volts, go to next step. If voltage is not 4-6 volts, go to TEST C, step 1).
11) Simulate Opposite Signal To PCM

Turn ignition switch to OFF position. Disconnect suspect temperature sensor. Connect a jumper wire between ECT or IAT sensor SIG and SIG RTN terminal at suspect sensor harness connector.
With scan tool installed, turn ignition switch to ON position.
NOTE: If a scan tool communication error is displayed, remove jumper wire and go to step 13).
Using scan tool, select ECT-V and IAT-V PID from PID/DATA MONITOR & RECORD menu. If PID value is less than.2 volt, replace suspect sensor. If PID value is.2 volt or more, remove
jumper wire and go to next step.
12) Check Temperature Sensor SIG & SIG RTN Circuits For Open

Turn ignition switch to OFF position. Ensure suspect temperature sensor is disconnected. Disconnect PCM connector(s). Inspect connector for loose, damaged or corroded terminals.
Repair as necessary. Using a DVOM, measure resistance of SIG RTN circuit between PCM harness connector SIG RTN terminal and suspect sensor harness connector SIG RTN terminal.
See Fig. 14-Fig. 18. See WIRING DIAGRAMS article.
Using a DVOM, measure resistance of SIG circuit between PCM harness connector ECT or IAT terminal and suspect sensor harness connector ECT or IAT terminal. If both resistance
measurements are less than 5 ohms, replace PCM. If either resistance measurement is 5 ohms or

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more, repair open in affected circuit.
13) Check Temperature Sensor SIG Circuit For Short To VREF

Turn ignition switch to OFF position. Disconnect PCM connector(s). Turn ignition switch to ON position. Using a DVOM, measure resistance between PCM harness connector VREF circuit
terminal and SIG circuit (ECT or IAT) at suspect sensor harness connector. See Fig. 14-Fig. 18. See WIRING DIAGRAMS article. If resistance is more than 10 k/ohms, replace PCM. If
resistance is 10 k/ohms or less, repair short to VREF in wiring harness.
NOTE: A break in step numbering sequence occurs at this point. Procedure
skips from step 13) to step 20). No test procedures have been omitted.
20) KOEO & KOER DTC P0117 Or P0112: Simulate Opposite Signal To PCM

DTC P0117 (ECT) or P0112 (IAT) indicates sensor signal is less than self-test minimum. Minimum signal for IAT and ECT sensor is.2 volt. Possible causes for these faults are: ? Circuit Grounded In Wiring Harness ? Faulty Sensor
? Faulty Connection ? Faulty PCM
Turn ignition switch to OFF position. Disconnect suspect temperature sensor connector. Inspect connector for loose, damaged or corroded terminals. Repair as necessary. Connect scan tool to
Data Link Connector (DLC). Turn ignition switch to ON position. Using scan tool, select ECT-V or IAT-V PID from PID/DATA MONITOR & RECORD menu. If PID value is 4.2 volts or less,
go to next step. If PID value is more than 4.2 volts, replace faulty temperature sensor.
21) Check VREF Circuit Voltage To TP Sensor

Turn ignition switch to OFF position. Disconnect TP sensor connector. Turn ignition switch to ON position. Using a DVOM, measure voltage between TP sensor harness connector VREF and
SIG RTN terminals. If voltage is 4-6 volts, connect TP sensor and go to next step. If voltage is not 4-6 volts, see TEST C, step 1).
22) Check Temperature Sensor SIG Circuit For Short To Ground

Turn ignition switch to OFF position. Ensure suspect sensor is disconnected. Disconnect PCM connector(s). Inspect connector for loose, damaged or corroded terminals. Repair as necessary.
Using a DVOM, measure resistance between PCM harness connector ECT or IAT sensor SIG circuit terminal and PCM PWR GND and SIG RTN terminals. See PCM PWR GND, SIG RTN
& VREF TERMINAL IDENTIFICATION table. If any resistance measurement is 10 k/ohms or less, repair short to ground. If all resistance measurements are more than 10 k/ohms, replace
PCM.
NOTE: A break in step numbering sequence occurs at this point. Procedure
skips from step 22) to step 80). No test procedures have been
omitted.

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NOTE: Ensure engine temperature is at ambient room temperature before performing this test step.
80) Continuous Memory DTC P0116: Check ECT Sensor Resistance With Engine Off DTC P0116 indicates ECT sensor drifted higher than normal sensor calibration curve and could
prevent one or more OBD-II monitors from functioning. PCM will set DTC P0116 when all of the following conditions are met: ? Engine coolant temperature at engine start up exceeds IAT temperature by more than calibrated value, about 30°F (1°C).
? Engine coolant temperature exceeds a calibrated value, about 225°F (107°C). ? Fuel, HEGO, catalyst and misfire monitors have not completed.
? Calibrated timer to set DTC P0116 has expired.
Possible causes for this fault are: ? Faulty ECT Sensor
? Coolant System Fault
Turn ignition switch to OFF position. Disconnect ECT sensor. Using a DVOM, measure resistance between ECT sensor SIG and SIG RTN circuit terminals. See IAT, ECT & EOT
SENSOR SPECIFICATIONS table. See Fig. 14. If resistance is not as specified, replace faulty ECT sensor. If resistance is as specified, go to next step.
NOTE: Engine must be at normal operating temperature before taking
temperature sensor measurements.
NOTE: A break in step numbering sequence occurs at this point. Procedure
skips from step 81) to step 90). No test procedures have been
omitted.
81) DTC P0116: Check ECT Sensor Resistance With Engine Running
Reconnect ECT connector. Start engine and operate at 2000 RPM for 2 minutes. Turn ignition switch to OFF position. Disconnect ECT sensor. Using a DVOM, measure resistance between
ECT sensor SIG and SIG RTN circuit terminals. See IAT, ECT & EOT SENSOR SPECIFICATIONS table. See Fig. 14. If resistance is not as specified, replace faulty ECT
sensor. If resistance is as specified, fault is not present at this time. Perform DRIVE CYCLE PROCEDURES under ADDITIONAL SYSTEM FUNCTIONS to determine if fuel, HEGO,
catalyst and misfire monitors can be executed. Repeat QUICK TEST.
90) Continuous Memory DTC P0112, P1112, P0113, P0117, P1117 Or P0118: Check For Intermittent

These DTCs indicate possible intermittent fault. Possible causes for these faults are: ? Faulty Sensor
? Faulty Sensor Connector
? Open Or Grounded Circuit In Harness ? Faulty PCM

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Connect scan tool to Data Link Connector (DLC). Turn ignition switch to ON position. Using scan tool, select ECT-V and IAT-V PID from PID/DATA MONITOR & RECORD menu. While
observing appropriate PID, tap on sensor and wiggle sensor connector to simulate road shock. If no change in PID voltage reading occurs, go to next step. If any change in PID voltage reading
occurs, turn ignition switch to OFF position. Inspect connectors for loose, damaged or corroded terminals. Repair as necessary. If connectors are okay, replace faulty temperature sensor. If
directed here for Continuous Memory DTCs P1112 and P1117, perform DRIVE CYCLE PROCEDURES under ADDITIONAL SYSTEM FUNCTIONS to verify repair. Repeat QUICK
TEST.
91) Check EEC-V Wiring Harness

While still observing PID, wiggle and bend small sections of wiring harness working toward PCM. If no changes in PID voltage reading occurs, go to next step. If changes in PID voltage
reading occurs, isolate fault and repair as necessary. If directed here for Continuous Memory DTCs P1112 and P1117, perform DRIVE CYCLE PROCEDURES under ADDITIONAL
SYSTEM FUNCTIONS to verify repair. Repeat QUICK TEST.
92) Inspect PCM & Wiring Harness Connectors

Turn ignition switch to OFF position. Disconnect PCM connector(s). Inspect connector(s) for damaged terminals, corrosion and loose terminals. If connectors and terminals are damaged, repair
as necessary. If directed here for Continuous Memory DTCs P1112 and P1117, perform DRIVE CYCLE PROCEDURES under ADDITIONAL SYSTEM FUNCTIONS to verify repair. Repeat
QUICK TEST. If connectors and terminals are okay, fault cannot be identified at this time. Testing is complete. If directed here for Continuous Memory DTCs P1112 and P1117, perform
DRIVE CYCLE PROCEDURES under ADDITIONAL SYSTEM FUNCTIONS to verify repair. Repeat QUICK TEST.
NOTE: A break in step numbering sequence occurs at this point. Procedure
skips from step 92) to step 100). No test procedures have been omitted.
100) Continuous Memory DTC P0125: Check Engine Coolant Level

This DTC indicates ECT sensor has not reached the required temperature level to enter closed loop operating conditions within a specified amount of time after starting engine. Possible causes
for this fault are: ? Insufficient Engine Warm-Up Time ? Thermostat Leaking Or Stuck Open
? Malfunctioning CHT Or ECT Sensor ? Low Coolant Level
Check and repair cooling system as necessary. Clear DTCs and repeat QUICK TEST.
NOTE: A break in step numbering sequence occurs at this point. Procedure skips from step 100) to step 110). No test procedures have been
omitted.

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110) DTC P1184: Check Operation Of EOT Sensor

This DTC indicates Engine Oil Temperature (EOT) sensor signal was out of self-test range. Correct range for measurement is.3-1.2 volt. Possible causes for this fault are: ? Faulty Sensor Or Connector ? Fault In Harness
? Faulty PCM
Connect scan tool. Start and operate engine at 2000 RPM until engine temperature becomes stabilized. Perform KOER ON-DEMAND SELF-TEST. If DTC P1184 is present, turn ignition
switch to OFF position and go to next step. If DTC P1184 is not present, engine oil temperature was not at operating temperature. Repair other DTCs as required.
111) DTC P0298, P1183 Or P1184: Check Temperature Signal

These DTC indicate engine oil temperature protection strategy in PCM has been activated by engine oil over-temperature condition. Possible causes for this fault are: ? Very High Engine RPM For An Extended Period Of Time ? Overheating Condition
? Fault In EOT Sensor Or Harness ? Base Engine Problems
Turn ignition switch to ON position (engine off). Using scan tool, select EOT-V PID from PID/DATA MONITOR & RECORD menu. If EOT-V PID voltage is less than.3 volt, go to next
step. If EOT-V PID voltage is.3 volt or more go to step 115).
112) Simulate Opposite EOT Signal To PCM

While monitoring EOT-V PID voltage, disconnect EOT sensor. If EOT-V PID voltage is more than 4.2 volts, replace EOT sensor. If EOT-V PID voltage is 4.2 volts or less, go to next step.
113) Check EOT SIG Circuit For Short To Ground

Turn ignition switch to OFF position. Disconnect PCM connector(s). Using a DVOM, measure resistance PCM harness connector terminals No. C39 (EOT) and No. C17 (SIG RTN) circuits. See
Fig. 15. Using a DVOM, measure resistance between PCM harness connector terminals No. C39 (EOT) and No. A24, A25, A26, A27 and A43 (PWR GND) circuits. See Fig. 3. If all resistance
measurements are more than 10 k/ohms, replace PCM. If any resistance measurement is 10 k/ohms or less, repair short to ground in affected circuit.
NOTE: A break in step numbering sequence occurs at this point. Procedure skips from step 113) to step 115). No test procedures have been
omitted.
115) Check For High EOT Signal

If EOT-V PID voltage is more than 4.2 volts, go to next step. If EOT-V PID voltage is 4.2 volts or less, go to step 120).

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116) Simulate Low Signal To PCM

Disconnect EOT sensor. Connect jumper wire between EOT sensor harness connector terminals (EOT and SIG RTN). Turn ignition switch to ON position. Using scan tool, access EOT-V PID
from PID/DATA MONITOR & RECORD menu. If EOT-V PID voltage is less than.3 volt, replace EOT sensor. If EOT-V PID voltage is.3 volt or more, go to next step.
117) Check EOT Sensor SIG & SIG RTN Circuits For Open

Turn ignition switch to OFF position. Disconnect PCM connector(s). Using a DVOM, measure resistance of EOT (SIG) circuit between PCM harness connector terminal No. C39 and EOT
sensor. See Fig. 15. Using a DVOM, measure resistance of SIG RTN circuit between PCM harness connector terminal No. C17 and EOT sensor. If each resistance measurement is less than
5 ohms, replace PCM. If either resistance measurement is 5 ohms or more, repair open in affected circuit.
NOTE: A break in step numbering sequence occurs at this point. Procedure skips from step 117) to step 120). No test procedures have been
omitted.
120) Intermittent EOT Sensor Check

While observing EOT-V PID, tap on EOT sensor and wiggle sensor connector to simulate road shock. If no large change in EOT-V PID voltage reading occurs, go to next step. If any large
change in EOT-V PID voltage reading occurs, turn ignition switch to OFF position. Inspect connectors for loose, damaged or corroded terminals. Repair as necessary. If connectors are okay,
replace EOT sensor.
121) Check EEC-V Wiring Harness

While still observing EOT-V PID, wiggle and bend small sections of wiring harness working toward PCM. If no large change in EOT-V PID voltage reading occurs, fault is not present at this
time. Perform DRIVE CYCLE PROCEDURES under ADDITIONAL SYSTEM FUNCTIONS to verify repair. Repeat QUICK TEST. If any large change in EOT-V PID voltage reading
occurs, isolate fault and repair as necessary. Clear DTCs and perform DRIVE CYCLE PROCEDURES under ADDITIONAL SYSTEM FUNCTIONS to verify repair. Repeat QUICK
TEST.
NOTE: A break in step numbering sequence occurs at this point. Procedure
skips from step 121) to step 130). No test procedures have been omitted.
130) DTC P0298: Engine Oil Over-Temperature Condition

Engine oil temperature protection strategy in PCM has been activated. Check for engine overheating condition or mechanical problem. If problem is found, repair as necessary. If problem
is not found, go to next step.
131) Check For EOT Sensor

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Page 10 of 10
Engine oil temperature strategy can be activated in PCM without an EOT sensor. Ensure vehicle is equipped with an EOT sensor. If vehicle is equipped, go to step 111). If vehicle is not equipped,
improper transmission gear selection or excessive RPM for extended period may have activated engine protection strategy in PCM.

Rivermikerat
Jan 2, 2012.