Diagnostic Aids

Perform this test when instructed by QUICK TEST or CIRCUIT TEST AA. This test is only intended to diagnose:

Fuel pump relay.
Inertia switch.
Wiring harness circuits (BATT +, VPWR, FUEL PUMP, GND and POWER-TO-PUMP).
ECA.

Fig 1: Fuel Pump Monitor Circuit Diagram (Typical)

Fig 2: Fuel Pump Monitor Ckt. Diagram (Escort & Tracer)

TEST PIN NO. 8 OR 19 (FPM) WIRE COLOR ID

Application	Wire Color
Escort & Tracer	Black/Pink

TEST PIN NO. 22 (FP) WIRE COLOR IDENTIFICATION

Application	Wire Color
Escort & Tracer	Light Green

TEST PIN NO. 37 & 57 (VPWR) WIRE COLOR ID

Application	Wire Color
Escort & Tracer	White/Red

Fig 3: Fuel Pump Monitor Ckt. Diagram (Cougar & Thunderbird)

TEST PIN NO. 8 (POWER-TO-PUMP) WIRE COLOR ID

Application	Wire Color
Cougar & Thunderbird	Pink/Black

TEST PIN NO. 22 (FP) WIRE COLOR IDENTIFICATION

Application	Wire Color
Cougar & Thunderbird	Tan/Light Green

Fig 4: Fuel Pump Monitor Ckt. Diagram (Crown Victoria, Grand Marquis & Town Car)

Fig 5: Fuel Pump Monitor Circuit Diagram (Mark VII)

Fig 6: Fuel Pump Monitor Circuit Diagram (Mustang)

1) No Fuel System Pressure: Check Fuel Pump Operation Turn ignition switch from OFF to RUN position several times (DO NOT turn to START position). If fuel pump runs briefly each time ignition is turned to RUN position, fuel pump circuit is okay. If fuel pump does not run, go to step 2).

2) Check For VPWR To ECA Turn ignition off. Install EEC-IV Breakout Box (T83L-50-EEC-IV). Connect ECA to breakout box. Turn ignition on. Measure voltage between test pins No. 37 and 40 at breakout box. Measure voltage between test pins No. 57 and 60 at breakout box. If both voltage readings are more than 10.5 volts, go to step 3). If voltage is 10.5 volts or less, go to CIRCUIT TEST B, step 1).

3) Check Voltage To POWER-TO-PUMP Circuit With ignition on, measure voltage between chassis ground and POWER-TO-PUMP circuit at fuel pump relay while cranking engine. If reading is less than 8 volts, go to step 4). If reading is 8 volts or more, check fuse to fuel pump relay. If fuse is okay, repair open in BATT+ circuit between fuel pump relay and battery positive terminal. Remove breakout box, and repeat QUICK TEST .

4) Checking BATT (+) Circuit To Fuel Pump Relay Turn ignition on. Leave breakout box installed and ECA connected. Locate fuel pump relay. Measure voltage between chassis ground and BATT (+) circuit at fuel pump relay. If voltage is less than 10.5 volts, repair open in BATT (+) circuit between fuel pump relay and positive battery terminal. Repeat QUICK TEST . If reading is 10.5 volts or more, go to step 5).

5) Check Voltage At POWER-TO-PUMP Circuit Turn ignition off. Connect jumper wire from test pin No. 22 to test pin No. 40 or 60 at breakout box. Turn ignition on. Measure voltage between chassis ground and POWER-TO-PUMP circuit at fuel pump relay. If voltage is 10.5 volts or more, replace ECA and repeat QUICK TEST . If voltage is less than 10.5 volts, replace fuel pump relay, and repeat QUICK TEST.

NOTE: A break in step numbering sequence occurs at this point. Procedure skips from step 5) to step 7). No test procedures have been omitted.

7) Code 87/556: Check VPWR To Fuel Pump Relay Code 87/556 indicates a fuel pump primary circuit failure. Possible causes for this fault are:

Inertia switch not reset or circuit open.
Open or shorted circuit.
Faulty fuel pump relay.
Faulty ECA.

Disconnect fuel pump relay. Turn ignition on. Measure voltage between chassis ground and VPWR circuit at fuel pump relay wiring harness connector. If reading is 10.5 volts or more, go to step 8). If reading is less than 10.5 volts, verify inertia switch is in ON position. If switch is okay, repair open in VPWR circuit between EEC power relay and fuel pump relay. Connect fuel pump relay and repeat QUICK TEST .

8) Check Fuel Pump Relay Turn ignition off. Disconnect fuel pump relay. See Fig 7 . Set DVOM on 200-ohm scale. On ISO relays, measure resistance between terminals No. 85 and 86. On all other relays, measure resistance between VPWR pin and FUEL PUMP circuit pin at fuel pump relay. Both resistances should be 40-85 ohms. Set DVOM to 20-k/ohm scale. On ISO relays, measure resistance between terminal No. 85 and terminals No. 30 and 87. On all other relays, measure resistance between FUEL PUMP circuit pin and both POWER-TO-PUMP and BATT (+) pins at fuel pump relay. All resistances should be greater than 10,000 ohms. If resistances are as specified, go to step 9). If resistances are not as specified, replace fuel pump relay and repeat QUICK TEST.

Fig 7: Fuel Pump Relay Connector Terminal ID

9) Check For Short To Power Turn ignition off. Disconnect fuel pump relay. Disconnect 60-pin ECA connector. Inspect terminals, and repair if damaged. Install EEC-IV Breakout Box (T83L-50-EEC-IV), leaving ECA disconnected. Turn ignition on. Measure voltage between test pin No. 22 and negative battery terminal. If voltage is less than 1.0 volt, go to step 10). If voltage is 1.0 volt or more, repair short circuit. Reconnect ECA, and attempt to start vehicle. If vehicle fails to start, replace ECA. Repeat QUICK TEST .

10) Check For Shorts To Ground Turn ignition off. Leave fuel pump relay disconnected. Measure resistance between test pin No. 22 and test pins No. 40 and 60. If resistance is less than 10,000 ohms, repair short in FUEL PUMP circuit. Remove breakout box, and repeat QUICK TEST . If resistance is 10,000 ohms or more, go to step 11).

11) Check Fuel Pump Circuit Continuity Turn ignition off. Leave fuel pump relay disconnected. Measure resistance between FUEL PUMP circuit at fuel pump relay wiring harness connector and test pin No. 22 at breakout box. If resistance is less than 5 ohms, replace ECA and repeat QUICK TEST . If resistance is 5 ohms or more, repair open circuit. Reconnect all components, and repeat QUICK TEST.

NOTE: A break in step numbering sequence occurs at this point. Procedure skips from step 11) to step 20). No test procedures have been omitted.

20) Code 95/542 A KOEO Code 95/542 indicates one of following conditions:

Due to internal circuitry of ECA, a left/front HEGO signal short to power could produce a Code 95/542 or 96/543.

35) Check Left/Front HEGO Sensor For Short To Power Turn ignition off. Disconnect left or front HEGO sensor. See Fig 1 . Measure resistance between HEGO SIGNAL terminal and KEY POWER terminal at HEGO sensor wiring harness connector. See Fig 2 . If resistance is 10,000 ohms or more, go to step 36). If resistance is less than 10,000 ohms, replace HEGO sensor. Clear KAM, and repeat QUICK TEST .

Fig 1: HEGO Sensor Connector

Fig 2: HEGO Sensor Vehicle Harness Connector

36) Check HEGO Circuit For Short To Power Turn ignition off. Disconnect ECA. Inspect and repair any damaged terminals. Turn ignition on. With left or front HEGO sensor disconnected, measure voltage between HEGO SIGNAL at HEGO wiring harness connector and chassis ground. If voltage is less than 2 volts, replace ECA and repeat QUICK TEST . If voltage is 2 volts or more, repair short circuit. Reconnect ECA and HEGO sensor. Clear KAM, and repeat QUICK TEST .

NOTE: A break in step numbering sequence occurs at this point. Procedure skips from step 36) to step 90). No test procedures have been omitted.

90) Continuous Memory Code 95/542 Code 95/542 indicates one of following conditions:

Faulty ground circuit at fuel pump.
FPM or POWER-TO-PUMP circuit short to power.
Fuel pump relay contacts stuck closed.
Open circuit in or between fuel pump and FPM circuit at ECA.
Left or front HEGO circuit short to power (dual HEGO system).
FUEL PUMP circuit is activated at a time that is not programmed into ECA strategy.

Start engine, and enter wiggle test. See CONTINUOUS MONITOR MODE (WIGGLE TEST) under QUICK TEST. Check for engine miss or intermittent fuel pump deactivation while performing following:

Shake and bend POWER-TO-PUMP circuit wiring harness connector between fuel pump relay and fuel pump.
Shake and bend fuel pump ground circuit between fuel pump and ground.
Lightly tap fuel pump to simulate road shock.
Lightly tap inertia switch to simulate road shock.

With ignition off, check harness connectors for corrosion and damage. Isolate and repair any faults. Clear continuous memory, and repeat QUICK TEST . If no faults are found, go to step 91).

91) Check FPM Circuit Turn ignition off. Disconnect ECA 60-pin connector. Inspect terminals, and repair if damaged. Install EEC-IV Breakout Box (T83L-50-EEC-IV), leaving ECA disconnected. Connect test light between test pin No. 8 (No. 19 on Escort, Mustang and Tracer) and test pin No. 37 at breakout box. With test light lit, perform wiggle test on FPM circuit between fuel pump and ECA. Light will go out if fault is found, indicating an open circuit. If a fault is found, repair as necessary and repeat QUICK TEST . If no fault is found, go to step 92).

92) Check For Shorts To Power Connect a test light between breakout box test pin No. 8 (No. 19 on Escort, Mustang and Tracer) and test pin No. 40. Test light should be off. Observe test light while bending and shaking FPM circuit and POWER-TO-PUMP circuit. Lightly tap fuel pump relay to simulate road shock. Fault is indicated if test light comes on. Isolate and repair fault as necessary, and repeat QUICK TEST . If no fault is found, go to step 96) (dual HEGO) or step 99) (single HEGO).

93) Continuous Memory Code 96/543: Check For Continuous Memory Code 87/556 If Code 87 or 556 is present, go to step 95). If Codes 87 and 556 are not displayed, go to step 94).

94) Check EEC-IV Harness A Continuous Memory Code 96/543, without an accompanying Continuous Memory Code 87/556, indicates one of following conditions has occurred during vehicle operation:

An open in BATT (+) circuit between BATT (+) and fuel pump relay.
Fuel pump relay contacts open.
Open in POWER-TO-PUMP circuit between fuel pump relay to FPM splice (if applicable).
Left/front HEGO circuit short to power (dual HEGO).

Start engine. Check for engine miss or intermittent fuel pump deactivation while performing following:

Shake and bend BATT (+) circuit wiring harness between power source and fuel pump relay.
Shake and bend POWER-TO-PUMP circuit wiring harness connector between fuel pump relay and FPM splice (if applicable).
Lightly tap fuel pump relay to simulate road shock.

Turn ignition off. Inspect all fuel pump relay and BATT (+) connectors for damage and corrosion. If fault is found, repair as necessary. Clear and repeat QUICK TEST . If no fault is found, a Continuous Memory Code 95/543 may have been set without a Continuous Memory Code 87/556 under certain conditions, even though a fault has occurred in fuel pump primary circuit. Go to step 95) for fuel pump primary circuit check.

95) Continuous Memory Code 87/556: Check EEC-IV Harness A Continuous Memory Code 87 or 556 indicates primary fuel pump circuit has failed during vehicle operation. Possible causes for this fault are:

Open in VPWR circuit between EEC power relay and fuel pump relay.
Open coil in fuel pump relay.
Open in fuel pump circuit (pin No. 22).
Faulty inertia switch.

Start engine. Check for engine miss or intermittent fuel pump deactivation while performing following:

Shake and bend VPWR circuit wiring harness between EEC and fuel pump relay.
Shake and bend FP circuit wiring harness connector between fuel pump relay and ECA.
Lightly tap fuel pump relay to simulate road shock.
Lightly tap inertia switch to simulate road shock (if equipped).

Turn ignition off. Disconnect ECA 60-pin connector. Inspect terminals, and repair if damaged. Install EEC-IV Breakout Box (T83L-50-EEC-IV), leaving ECA disconnected. If fault is found, isolate and repair as necessary. Repeat QUICK TEST . If no faults are found but Code 96/543 is found, go to step 96) (dual HEGO). If fault can not be duplicated at this time, go to step 99) (all others).

Due to internal circuitry of ECA, an intermittent left/front HEGO signal short to power could produce a Continuous Memory Code 95/542 or 96/543.

96) Check Left/Front HEGO Circuit For Short To Power Turn ignition off. Breakout box should be installed with ECA disconnected. Connect test light between left/front HEGO test pin and pin No. 40 at breakout box. Test light should be off. Observe test light while bending and shaking left/front HEGO circuit from HEGO sensor to ECA. Lightly tap HEGO SENSOR to simulate road shock. Fault is indicated if test light comes on. Isolate and repair as necessary. Clear Keep-Alive Memory (KAM), and repeat QUICK TEST . If no fault is indicated, go to step 99).

NOTE: A break in step numbering sequence occurs at this point. Procedure skips from step 96) to step 99). No test procedures have been omitted.

WARNING: Following road test is an optional procedure. Follow all applicable safety procedures and traffic laws. This road test requires a driver and an assistant. Assistant should make measurements, observe changes and record notes. If this test is not performed, go to TESTS W/O CODES article in the ENGINE PERFORMANCE Section for other possible causes.

99) Road Test Vehicle Purpose of this test is to identify faults by monitoring certain controlled parameters while trying to recreate a driveability or MIL light symptom. To prepare for road test:

Install fuel pressure gauge.
Install MAP/BP tester.
Disconnect ECA 60-pin connector, install breakout box and reconnect ECA to breakout box.
Connect "T" vacuum gauge into manifold vacuum line.
Have DVOM, writing materials and appropriate schematics and pin voltage charts available.

With ignition on and negative lead of DVOM connected to negative battery terminal, ensure following signals are correct:

POWERS: KAPWR (pin No. 1) is greater than 10.5 volts, VPWR (pins No. 37 and 57) is greater than 10.5 volts and VREF (pin No. 26) is 4-6 volts.
GROUNDS: PWR GND (pins No. 40 and 60), SIG RTN (pin No. 46) and IGN GND (pin No. 16) are 0.0-0.5 volt.
OPTIONAL GROUNDS: HEGO GND (pin No. 49), CSE GND (pin No. Step 20) and MAF RTN (pin No. 9 or 15) are 0.0-0.5 volt.

Test lights and DVOM are useful during diagnosis. For example: with Continuous Memory Code 87/556 (fuel pump primary circuit failure) and a surge or stall symptom, connect a test light to fuel pump relay between VPWR and ground. Connect DVOM between FP circuit at fuel pump relay and breakout box test pin No. 1. Under normal driving conditions, test light will be on and DVOM will read battery voltage. If vehicle stalls, ECA will open FP circuit and DVOM voltage will be low. If fault is in fuel pump circuit, test light and DVOM status will change as fault occurs. If test light at VPWR circuit goes out, fault is in VPWR circuit to fuel pump relay. If test light and DVOM status do not change and Continuous Memory Code 87/556 is set again, replace fuel pump relay. If only FP voltage goes low, fault is in FP circuit or ECA. To diagnose FP circuit and ECA, connect DVOM between breakout box test pin No. 1 and 22. If voltage goes low as symptom occurs, replace ECA. If voltage stays high as symptom occurs, fault is in FP circuit. For fuel pump secondary circuit Codes 95/542 and 96/543, circuits BATT (+), POWER-TO-PUMP and FPM can be diagnosed using same procedure. Drive vehicle and attempt to induce symptom. Information provided by vehicle operator may help when trying to recreate symptom. When symptom occurs, assistant should observe and record changes in voltage signals. Information about symptom and operating condition value of voltage signal and any other information available should be recorded for analysis. If unable to duplicate symptom during road test, verify EEC-IV values are within acceptable range. After test is completed, analyze results to locate and repair fault causing symptom. If problem cannot be identified, go to TESTS W/O CODES article in the ENGINE PERFORMANCE Section other possible causes of symptom.