Diagnostic Aids

WARNING: This page does not describe the selected car, but rather 26 other vehicles, including the 1999 Mercury Tracer, 1999 Mercury Sable, 1999 Mercury Mystique, 1999 Mercury Mountaineer, and 1999 Mercury Grand Marquis. However, it is still accessible from the selected car via links, so may be relevant.

Perform this test only when directed by QUICK TEST. EFT sensor will operate within the range of -40 to 275°F (-40 to 135°C). This system test is intended to diagnose the following components and circuits:

EFT sensor.
Wiring harness circuits (EFT and SIG RTN).
Powertrain Control Module (PCM).

PCM EFT TERMINAL IDENTIFICATION

Application	PCM Terminal No.
Gasoline Vehicles	10
Natural Gas Vehicles	62

EFT SENSOR SPECIFICATIONS⁽¹⁾

Temperature °F (°C)

Volts

Ohms

50 (10)

3.51

58,750

68 (20)

3.07

27,300

86 (30)

2.60

24,270

104 (40)

2.13

16,150

122 (50)

1.70

10,970

140 (60)

1.33

7700

158 (70)

1.02

5370

176 (80)

0.78

3840

194 (90)

0.60

2800

212 (100)

0.46

2070

248 (120)

0.27

1180

⁽¹⁾	Values may vary by 15 percent.

NOTE: Fuel Rail Pressure (FRP) sensor may also be known as Injection Pressure (IP) sensor. Engine Fuel Temperature (EFT) sensor may also be known as Fuel Rail Temperature (FRT) sensor.

1) DTC P0181: Check For KOER DTCs

This DTC indicates sensor signal is greater than self-test maximum. Check for following possible causes:
- Open circuit in wiring harness.
- Faulty wiring harness connector.
- Faulty EFT sensor.
- Faulty PCM.
Start engine. Ensure engine is at normal operating temperature. Perform KOER ON-DEMAND SELF-TEST . If DTC P0182 or P0183 is present with DTC P0181, go to next step. If only DTC P0181 is present, clear DTCs. Perform OBD-II DRIVE CYCLE. See DRIVE CYCLES under ADDITIONAL SYSTEM FUNCTIONS. Repeat QUICK TEST .

2) DTC P0180, P0181, P0182 Or P0183

These DTCs indicate sensor signal is greater or less than self-test maximum. Check for following possible causes:
- Open or short circuit in wiring harness.
- Faulty wiring harness connector.
- Faulty EFT sensor.
- Faulty PCM.
Turn ignition off. Disconnect EFT sensor connector. With scan tool connected, turn ignition on.

NOTE: If scan tool communication link error is displayed, remove jumper wire and go to step 5).

Using scan tool, select EFTA V PID from PID/DATA monitor menu. Note PID value. Connect a jumper wire between signal circuit (EFT A) terminal and SIG RTN terminal at EFT sensor wiring harness connector. If PID value is more than 4.5 volts with sensor disconnected and less than .2 volt with jumper wire connected, replace EFT sensor. If PID value is not as specified, proceed as follows.
- For DTC P0182, go to next step.
- For DTC P0183, go to step 5).
- If PID value is less than 4.5 volts with EFT sensor disconnected, go to next step.
- If PID value is more than .2 volt with jumper wire connected, go to step 5).

3) Check VREF Circuit Voltage At Fuel Rail Pressure (FRP) Sensor

Turn ignition off. Disconnect FRP sensor connector. Turn ignition on. Measure voltage between ground and VREF terminal at FRP sensor wiring harness connector. See Fig 2 or Fig 3 . If voltage is 4-6 volts, connect FRP sensor and go to next step. If voltage is not 4-6 volts, go to TEST C .

4) Check Signal Circuit For Short To Ground

Turn ignition off. Ensure EFT sensor is disconnected. Disconnect PCM 104-pin connector. Inspect connector for loose, damaged or corroded terminals. Repair as necessary. Measure resistance between PCM connector pin for EFT circuit and PCM connector pin No. 91. See PCM EFT TERMINAL IDENTIFICATION table. Also measure resistance between PCM connector pin for EFT A circuit and ground. If both resistance readings are more than 10,000 ohms, replace PCM. If any resistance reading is 10,000 ohms or less, repair short to ground.

5) Check EFT Signal For Short To VREF

Measure resistance between test pin for EFT A circuit and test pin No. 90 at breakout box. See PCM EFT TERMINAL IDENTIFICATION table. If resistance is more than 10,000 ohms, go to next step. If resistance is 10,000 ohms or less, repair short to VREF circuit.

6) Check For Open Circuit

Measure resistance of EFT A circuit between PCM connector pin for EFT A circuit and EFT sensor wiring harness connector. Refer to the PCM EFT TERMINAL IDENTIFICATION table in this article. See Fig 1. Also measure resistance of SIG RTN circuit between EFT sensor wiring harness connector and PCM connector pin No. 91. If both resistance readings are less than 5 ohms, replace PCM. If any resistance reading is 5 ohms or more, repair open circuit.

7) Continuous Memory DTC P0180, P0181, P0182 Or P0183

These DTCs indicate possible intermittent fault. Possible causes for these faults are:
- Faulty sensor.
- Faulty sensor connector.
- Faulty wiring harness.
- Faulty PCM.
Turn ignition on. Using scan tool, select EFTA PID from PID/DATA monitor menu. While observing PID, tap on sensor to simulate road shock. Wiggle sensor connector. If no change in temperature reading occurs, go to next step. If any change in temperature occurs, inspect connectors for loose, damaged or corroded terminals. Repair as necessary. If connectors are okay, replace EFT sensor.

8) Check Sensor Wiring Harness

While observing EFTA PID, wiggle and bend small sections of wiring harness working toward PCM. If fault is indicated, isolate fault and repair as necessary. If no fault is found, fault cannot be identified at this time. Testing is complete.

Fig 1: Identifying Engine Fuel Temperature (EFT) Sensor Connector Terminals

Courtesy of FORD MOTOR CO.

Fig 2: Identifying Fuel Rail Pressure (FRP) Sensor Connector Terminals (Natural Gas Vehicles)

Courtesy of FORD MOTOR CO.

Fig 3: Identifying Fuel Rail Pressure (FRP) Sensor Connector Terminals (Except Natural Gas Vehicles)

Courtesy of FORD MOTOR CO.