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HOMESERVICE MANUALSMERCURY1991TRACER BASE, 4D SEDAN, AUTOMATICREPAIR AND DIAGNOSISEXTERNAL PAGESDIFFERENT CARSECTION 4 (ENGINE CONTROLS - TESTS W/CODES - EEC-IV)CIRCUIT TESTSCIRCUIT TEST DA - TEMPERATURE SENSOR TEST (ACT & ECT)DIAGNOSTIC AIDS
1991 Mercury Tracer Base, 4D Sedan, Automatic

Diagnostic Aids

1991 Mercury Tracer Base, 4D Sedan, AutomaticSECTION Diagnostic Aids
WARNING: This page does not describe the selected car, but rather 15 other vehicles, including the 1992 Mercury Tracer, 1992 Mercury Topaz, 1992 Mercury Sable, 1992 Mercury Grand Marquis, and 1992 Mercury Cougar. However, it is still accessible from the selected car via links, so may be relevant.

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 ACT and VAT sensors. Engine coolant temperature must be greater than 50°F (10°C) to pass KOEO SELF-TEST and greater than 180°F (82°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% due to sensor and VREF variations.

This circuit test is intended to diagnose following components and circuits:

  • Air Charge Temperature (ACT) sensor.
  • Engine Charge Temperature (ECT) sensor.
  • Vehicle harness circuits (ACT, ECT and SIG RTN).
  • Electronic Control Assembly (ECA).

To prevent replacing good components, ensure following non-EEC areas or components are not cause of problem:

  • Coolant level low.
  • Cooling system, water pump or fan.
  • Electro drive cooling fan.
  • Engine operating temperature low.
  • Engine oil level low.
  • Thermostat.
  • Air cleaner duct.
  • Ambient temperature too low.
Fig 1: Temperature Sensor Circuit & Connector Terminal ID
G200169
TEST PIN NO. 7 (ECT) WIRE COLOR IDENTIFICATION

Application Wire Color
Probe 3.0L (1) Yellow/Red
1.9L Blue/White
Except 1.9L & Probe 3.0L Light Green/Red
(1) ECT wire may also be Yellow/Black.
TEST PIN NO. 25 (ACT) WIRE COLOR IDENTIFICATION

Application Wire Color
1.9L White/Green
2.3L Gray
3.0L
Probe (1) Yellow
Sable & Taurus (Except SHO) Light Green/Purple
Taurus SHO, Tempo & Topaz Gray
3.8L Light Green/Purple
4.6L
Crown Victoria & Grand Marquis Light Green/Purple
Town Car Gray
5.0L
Cougar & Thunderbird Light Green/Purple
Mark VII & Mustang Gray
(1) ACT wire may also be White/Light Green.
TEST PIN NO. 46 (SIG RTN) WIRE COLOR IDENTIFICATION

Application Wire Color
Probe 3.0L (1) Light Green/Yellow
1.9L Light Green/Black
Except 1.9L & Probe 3.0L Gray/Red
(1) SIG RTN wire may also be Black/Blue.

1) Code 21/116 Or 24/114:  Code 21/116 (ECT) or 24/114 (ACT) indicates corresponding sensor is out of self-test range. Correct range for measurement is .3-3.7 volts. Check for following possible causes:

  • Low ambient temperature (less than 50°F).
  • Low coolant level.
  • Faulty harness connector.
  • Faulty sensor.
  • ACT sensor improperly mounted in air cleaner.

If vehicle cannot be started, go to step 3). If vehicle stalls, go to CIRCUIT TEST S. Ensure upper radiator hose is hot and pressurized. Repeat QUICK TEST  . If Code 21, 24, 114 or 116 is present, go to step 2). If none of these codes are present, service other codes as necessary.

2) Check VREF Circuit Voltage At TPS  Turn ignition off. Disconnect Throttle Position Sensor (TPS). With ignition on and engine off, measure voltage at TPS vehicle harness connector between VREF and SIG RTN. See Fig 2 . If voltage is 4-6 volts, reconnect TPS and go to step 3). If voltage is not 4-6 volts, go to CIRCUIT TEST C.

3) Check Temperature Sensor Resistance (KOEO)  Turn ignition off. Disconnect suspect sensor. Measure resistance between sensor signal circuit and SIG RTN circuit at sensor. If resistance is not within specification, replace suspected sensor. See Fig 3 . Reconnect vehicle harness, and repeat QUICK TEST. If resistance is within specification, perform following step as applicable.

  • For diagnosing vehicles with ECT sensor and a no-start condition, DO NOT service Code 21/116 at this time. Go to CIRCUIT TEST AA for TFI, CIRCUIT TEST AB for DIS and CIRCUIT TEST AC for EDIS.
  • For other vehicles, go to step 4).
Fig 2: TPS Harness Connector Terminal ID
G90B10950
RENDER: 1.0x

NO RELATED

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When to See a Mechanic

Stop DIY work and contact a certified mechanic immediately if any of the following apply:

  • • You smell fuel, burning insulation, or see smoke.
  • • Brakes feel soft, pull hard to one side, or make grinding noises.
  • • The engine overheats, stalls repeatedly, or misfires under load.
  • • You are missing required tools, torque specs, or safe lifting equipment.
  • • You are not confident in the next step or safety outcome.